Genetic advancements in breast cancer treatment: a review

Abstract

Breast cancer (BC) remains a leading cause of cancer-related deaths among women globally, highlighting the urgent need for more effective and targeted therapies. Traditional treatments, including surgery, chemotherapy, and radiation, face limitations such as drug resistance, metastasis, and severe side effects. Recent advancements in gene therapy, particularly CRISPR/Cas9 technology and Oncolytic Virotherapy (OVT), are transforming the BC treatment landscape. CRISPR/Cas9 enables precise gene editing to correct mutations in oncogenes like HER2 and MYC, directly addressing tumor growth and immune evasion. Simultaneously, OVT leverages genetically engineered viruses to selectively destroy cancer cells and stimulate robust antitumor immune responses. Despite their potential, gene therapies face challenges, including off-target effects, delivery issues, and ethical concerns. Innovations in delivery systems, combination strategies, and integrating gene therapy with existing treatments offer promising solutions to overcome these barriers. Personalized medicine, guided by genomic profiling, further enhances treatment precision by identifying patient-specific mutations, such as BRCA1 and BRCA2, allowing for more tailored and effective interventions. As research progresses, the constructive interaction between gene therapy, immunotherapy, and traditional approaches is paving the way for groundbreaking advancements in BC care. Continued collaboration between researchers and clinicians is essential to translate these innovations into clinical practice, ultimately improving BC patients' survival rates and quality of life.

Introduction

Breast cancer (BC) is the second most frequent cancer globally, accounting for a significant part of cancer-related fatalities [1]. BC is the most common cancer in women worldwide [2]. In 2024, it is estimated that around 310,720 women in the U.S. were diagnosed with invasive BC, alongside 56,500 cases of ductal carcinoma in situ (DCIS). Additionally, BC is expected to claim the lives of 42,250 women. A significant portion of invasive BC cases (84%) and fatalities (91%) will be among women aged 50 and above, with nearly half (52%) of all deaths occurring in those aged 70 and older [3]. BC ranks as the second most common cause of cancer-related deaths in women in the United States [4]. Among women, it ranks as the top cause of mortality for those under 40 and the second most significant cause for those over 40 [5].

While current treatments are effective in the early stages, metastatic BC poses obstacles owing to resistance and restrictions, prompting the investigation of alternative therapies. Palliative methods have become the only choice for later stages, as intensive systemic medications exhibit poor response rates and long-term toxicity, affecting quality of life [6, 7]. The urgent requirement for novel therapies has led to the investigation of Oncolytic Viruses (OVs) derived or genetically designed to target and fight cancer cells [8].

Following BC diagnosis, the typical treatments include a combination of surgery, radiation, chemotherapy, endocrine therapy, targeted therapy, or a combination of them all [9, 10]. Cancer treatments like chemotherapy and radiation therapy are frequently insufficient and can be debilitating, as they also harm healthy, rapidly dividing cells during the treatment process [11]. The profound drawbacks of traditional cancer treatments, including systemic toxicity, reduced quality of life, and severe side effects, raise major concerns about these conventional approaches to cancer care. Due to the growth of knowledge and technological progress in cancer biology, new and safer anti-cancer strategies like immunotherapy, gene therapy, and targeted therapy are quickly developing to overcome the shortcomings of traditional treatments. Although traditional anti-cancer therapies have benefited from technological advancements, there is still a need for more precise and targeted approaches to cancer treatment [12]. Some natural compounds have also demonstrated anticancer effects and hold the potential for use as therapeutic agents [13].

The spread of BC is affected by irregular gene expression that triggers downstream signaling pathways [14]. Germline mutations occur more frequently in genes, regardless of their sensitivity to penetrance, while somatic mutations arise during an individual's lifetime and encompass both genomic and epigenetic changes [15, 16]. These genetic and epigenetic modifications influence the metabolic needs of cancer cells, such as changes in lipid metabolism, which contribute to increased proliferation and tumor formation [17]. Gene therapy focuses exclusively on cancerous cells for treatment, sparing healthy cells from being targeted [11].

Since gene changes and gene expression patterns underlie BC development and progression, repairing faulty genes and regulating gene expression using gene therapy is a viable treatment route [18]. Gene therapy, which involves transferring genetic components to treat illnesses or improve the clinical condition of patients, stands out as a remarkable technique for tackling BC and other medical issues [19].

Between 1963 and 1990, recombinant DNA technology emerged, paving the stage for gene therapy. Since 1989, more than 900 authorized clinical studies, including gene therapy techniques, have been completed globally. Since the unique role of genetic alterations and gene expression patterns in BC development, gene therapy has shown extraordinary success in treating this specific cancer type [18]. Mammalian cell culture and microbial fermentation systems are widely used to produce recombinant proteins commercially [20]. Gene Correction, Suicide Gene Therapy, Gene Suppression and Silencing, Decoy Oligodeoxynucleotide-mediated transcription factor targeting, miRNA targeting, BC cell targeting via aptamers, and DNA or RNA vaccination are some of the gene therapy strategies used to treat cancer, such as BC [21]. This study reviews the critical function of gene therapy, concentrating primarily on the latest developments in CRISPR/Cas9 technology and oncolytic virotherapy (OVT).

CRISPR/Cas9 technology and applications

The abbreviation 'CRISPR/Cas9' refers to Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR-associated protein 9, recognized for its enormous potential in genome editing. CRISPR/Cas9 technology shows promise for gene therapy, notably in tackling cancer, infections, and genetic disorders [22]. The technique enables genome editing for comprehensive disease discovery and analysis. In bacteria and archaea, the natural immune defence system (acquired) is mediated by RNA, known as CRISPR/Cas9 [23, 24]. During the immune response, short fragments of foreign DNA are incorporated into the host chromosome's CRISPR repeat spacer as new spacers after exposure to genetic material from plasmids or phages. This enables the host cell to retain a “memory” of the invader, protecting against future infections by the same pathogen [25, 26]. Single-guide RNAs (Cr and Cas9 nuclease) are the main components of CRISPR/Cas9, as the name [27]. It encodes a guide RNA, and when it targets a specific region of DNA, double-strand breaks (DSBs) are created. DSBs are produced by directly binding a target DNA sequence to the Cas9 nuclease [28, 29]. DSBs can be joined using two distinct mechanisms: homologous directed repair (HDR) [30] for homologous sequences and non-homologous end joining (NHEJ) [31] for non-homologous sequences (Fig. 1).

Fig. 1.

Overview of the CRISPR/Cas9 System

The organizational structure of CRISPR/Cas9 plays an essential role in monitoring gene activity during various disease states, repairing genes with damaging mutations, and controlling the activation or repression of malignancy genes [22, 32]. The precise genetic alterations made possible by CRISPR/Cas9 gene editing have transformed several industries, including medicine. It has been used to cure hereditary hematological conditions like sickle cell anemia and thalassemia by directly repairing cell mutations [33].

It is thought that CRISPR/Cas9 can be used to treat cancer. Different tumors, including brain, kidney, colorectal, hepatic, and bladder cancers, are being treated with it all over the world [34]. This technology can be utilized to develop cancer models for simulating cancer-related events, studying cancers [35], or modifying genes [36]. This technique also applies to tracing tumor cell lineages and exploring their evolutionary dynamics [37]. Some studies have shown that targeting factors involved in drug resistance using the CRISPR/Cas9 gene editing technique can significantly enhance the effectiveness of anticancer drugs [38]. Moreover, it is also applicable in cancer diagnosis, identifying genetic interactions in cancers [9]. Therefore, it is foreseeable that CRISPR technologies could be a robust tool for drug clinical application and development [39].

Oncolytic viruses and applications

In the twentieth century, cancer patients who contracted viral infections saw improvements and unexpected increases in their life expectancy, which led to the first unintentional observation of the oncolytic capabilities of specific viruses [40]. OVs are viruses that, through several biological processes, target and lyse tumor cells while sparing healthy ones [41] (Fig. 2). These viruses can target cancer cells and can replicate and deliver within cancer cells and tissues [42]. These viruses can activate the immune system to attack tumors and malignant cells, replicating the virus within the host cell and causing the malignant cell to break and release cancer antigens [43]. They must be non-pathogenic, proficient in targeting and eliminating cancerous cells, and capable of expressing tumor-killing factors through genetic engineering [44, 45].

Fig. 2.

Overview of OV Mechanism

OVs can occur naturally or be engineered in the laboratory by altering natural viruses. These modifications have ushered in a new era of less toxic, targeted virus-based therapies for cancer [46]. Based on the ability of OVs to eradicate cancerous cells, virotherapy is a new and exciting cancer treatment method [47]. Genetic engineering facilitates the development of tumor-selective OVs, ensuring increased efficacy and safety [48].

OVT is a novel approach to cancer treatment that uses naturally occurring or genetically modified viruses to target and kill cancer cells while preserving healthy tissues. In preclinical models, for example, oncolytic adenoviruses designed to interfere with tumor-specific pathways, such as TGF-β, have demonstrated encouraging outcomes by boosting antitumor immunity and working with treatments like CAR-T cells [49, 50]. The ability to specifically infect tumor cells and release immunostimulatory chemicals like cytokines to enhance the immune response further has also been shown by herpes simplex viruses (HSV) that have been altered to target receptors like HER2 and EGFR [50]. Furthermore, it has been demonstrated that OVs combined with immune checkpoint inhibitors, like PD-1 or CTLA-4 blockers, can overcome immunotherapy resistance and improve therapeutic efficacy in tumors, including BC and glioblastoma [50]. Because infected tumors release neoantigens that activate T-cell responses against cancer cells, this strategy also improves systemic antitumor immunity [49]. OVT is showing promise in broadening the range of treatments for solid tumors and hematological malignancies, providing fresh hope in oncology with current clinical trials [49, 50].

CRISPR/Cas9 in BC treatment

CRISPR/Cas9, with various targeting capabilities, offers excellent potential for repairing BC-related mutations [51]. Proto-oncogenes, which regulate cell proliferation and differentiation, can be converted into oncogenes through amplifications, translocations, and mutations, leading to their permanent activation and altered cellular functions that promote tumorigenesis. In BC, oncogenes such as HER2, MYC, CXCR4, ACKR3, MAP3K11, and OPN are commonly deregulated. CRISPR/Cas9 can target these oncogenes to inhibit cell proliferation and tumorigenicity [52]. The HER2 and MYC genes are frequently amplified in BC, and their co-amplification is associated with aggressive clinical behavior and poor prognosis. Therefore, these genes play a crucial role in BC [53]. Given the significant role of these oncogenes in various stages of BC, including tumor progression, metastasis, and treatment resistance, the following section reviews some studies on CRISPR/Cas9 related to them.

HER2 amplification/overexpression has been identified as an oncogenic driver and potential therapeutic target in BC patients [54]. Some studies have used CRISPR/Cas9 to target the HER2 gene in HER2-amplified BC cell lines. One study demonstrated that CRISPR/Cas9 targeting HER2 inhibited cell growth in HER2-positive cell lines (BT474 and SKBR3) by inducing a frameshift mutation in exon 12, leading to a truncated HER2 protein. Additionally, cell proliferation was suppressed via the MAPK-ERK pathway. Targeting exons 5, 10, and 12 of HER2 using CRISPR/Cas9 significantly reduced cell growth in HER2 + BC cells but not in HER2- cells (MCF7), indicating its potential as a therapeutic strategy for HER2 + BC [55]. A study demonstrated that the CRISPR/Cas9 system can directly target the HER2 oncogene in BC, inhibiting cell growth in cell lines with HER2 amplification. The addition of PARP inhibitors enhanced the inhibitory effect. Interestingly, CRISPR-induced mutations did not significantly affect HER2 protein expression levels. Instead, the effect appeared to be mediated by a dominant-negative mutation, which interfered with the MAPK/ERK signaling axis downstream of HER2. This study provides a novel mechanism underlying the anti-cancer effects of HER2 targeting by CRISPR/Cas9, distinct from the clinical drug Herceptin. It suggests incomplete CRISPR targeting of specific oncogenes could still have therapeutic value by generating dominant-negative mutants [55]. Another study investigates the effects of Her2/neu gene knockout in BC using the CRISPR/Cas9 system. In this study, the Her2/neu gene was knocked out in two BC cell lines (T47D and SKBR3) using CRISPR/Cas9, and gene expression profiles were analyzed using whole transcriptome amplification (WTA). The results revealed significant changes in downstream gene expression pathways following Her2 knockout [56] (Table 1).

Table 1.

Application of CRISPR/Cas9 in BC treatment

Study	Target Gene	Approach
HER2 targeting HER2 + BC cell lines	HER2	CRISPR/Cas9 induces frameshift mutation, reducing growth
HER2 targeting PARP inhibitors	HER2	CRISPR/Cas9 targeting PARP inhibitors, interfering with MAPK/ERK
HER2/neu knockout in BC using CRISPR/Cas9	HER2	CRISPR/Cas9 knockout followed by gene expression analysis
MYC gene editing in BC	MYC	CRISPR/Cas9 modification of MYC enhancer site to reduce proliferation
CRISPR/Cas9 + single-cell RNA sequencing in BC	MYC	Screening to identify driver gene cooperation in MYC-driven cells
MYC-driven BC survival protein screening	MYC	Pooled CRISPR/Cas9 screen to find essential RNA-binding proteins for MYC-driven BC survival

MYC is an oncogene frequently amplified in BC and associated with apoptosis inhibition and cell proliferation activation. CRISPR/Cas9 technology for MYC gene editing involves epigenetic modifications or elimination of the MYC enhancer docking site, leading to reduced cell proliferation and decreased MYC protein expression [57]. A study showed that disrupting E-box sites in the MCF7 BC cell line affected MYC binding, target gene expression, and tumor growth, suggesting that this approach could be a valuable tool for identifying MYC-dependent networks in cancer cells [58]. A CRISPR/Cas9 screening combined with single-cell RNA sequencing was performed in engineered human mammary epithelial MCF10A-MYC cells to determine how different driver genes cooperate and how the combination of inactivated tumor suppressor genes affects the oncogenic properties and transcriptome of mammary epithelial cells [59]. In a study, a pooled CRISPR/Cas9 screen targeting over 1000 RNA-binding proteins identified key proteins essential for the survival of MYC-driven BC cells, including TNBC. They found that depletion of the RNA-binding protein YTHDF2 induced apoptosis in TNBC cell lines and inhibited the growth of TNBC xenografts in vivo. The study highlighted YTHDF2 as a potential therapeutic target due to its role in promoting tumorigenesis and epithelial-mesenchymal transition (EMT) [60] (Table 1).

Advantages and challenges of CRISPR/Cas9 in BC treatment

CRISPR/Cas9 directly delivers a gene editing machine into target cells via in vivo or ex vivo procedures, resulting in permanent gene insertion, correction, or inactivation [32]. In a study, CRISPR/Cas9, a potent tool for precise genome editing, could better edit hPSC lines with facilitated delivery approaches than TALENs. The efficiency and mutagenesis of CRISPR/Cas9 were approximately 45–51% and 51–79% higher than TALENs, respectively [61].

On the other hand, CRISPR/Cas9 presents obstacles, particularly off-target effects (OTE) caused by unintentionally binding to undesirable genomic regions, which increase the risk of fatal mutations [32]. The necessity of a PAM sequence can restrict potential target sites, even though SpCas9, widely used in CRISPR technology, can detect a short PAM sequence (5'-NGG-3'). While viral vectors are still crucial for CRISPR therapy, concerns about insertional mutagenesis and immunological responses continue [22, 62].

In 2018, He Jiankui announced the birth of gene-edited infants in China using CRISPR technology, raising ethical issues. The twins received the CRISPR-knockout CCR5 gene to prevent HIV, smallpox, and cholera. Ethical arguments developed about the potential effects on the subjects and future generations, raising concerns about rights and the inheritance of mutations with unknown consequences [63].

Oncolytic viruses in BC treatment

BC is a commonly studied cancer for OV research. For BC, viruses from different Baltimore classification groups, including double-stranded DNA (dsDNA), double-stranded RNA (dsRNA), positive-sense single-stranded RNA (+ ssRNA), and negative-sense single-stranded RNA (-ssRNA), can be utilized for OVT [64]. In OVT, dsDNA and dsRNA viruses have gained attention due to their ability to replicate and destroy cancer cells, particularly in BC [1]. Below is a summary of the review on dsDNA and dsRNA OVs in BC treatment.

dsDNA viruses such as Adenovirus have distinct replication processes [65]. Oncolytic adenoviruses target cancer using two main strategies: transductional targeting, which enables specific infection of cancer cells, and transcriptional targeting, allowing viral replication specifically within cancer cells [66].

A study reported an oncolytic adenovirus transductionally targeted through a chimeric fiber and engineered to encode a full-length antibody against HER2. The virus effectively killed HER2 + BC cells in vitro and demonstrated significant anti-tumor effects in mice [67]. Another oncolytic adenovirus for BC was studied, with its fiber protein modified to include the Lyp-1 peptide, reducing hepatic toxicity and increasing infection of BC cells that express high levels of the Lyp-1 receptor. Additionally, the virus was engineered to encode a decoy of transforming growth factor-beta (TGF-β). This virus induced a potent anti-tumor response in murine triple-negative BC models and enhanced anti-PD-L1 and anti-CTLA-4 therapy [68]. Another study showed that an oncolytic adenovirus armed with the cytokine IL-24 could potently inhibit the growth of BC cells in vitro and mice [69] (Table 2).

Table 2.

Application of OVs in BC treatment

Study	Virus	Approach
Oncolytic adenovirus targeting HER2	Adenovirus	Full-length HER2 antibody; anti-tumor effects in vitro and in vivo
Oncolytic adenovirus with Lyp-1 peptide and TGF-β decoy	Adenovirus	Lyp-1 peptide for reduced toxicity; TGF-β decoy enhances anti-tumor response
Oncolytic adenovirus with IL-24 cytokine	Adenovirus	Armed with IL-24 cytokine; inhibits BC cell growth
Reovirus + topoisomerase inhibitors	Reovirus	Enhanced infectivity and cytotoxicity in TNBC; activates DNA damage response
Reovirus + PD-1 blockade	Reovirus	Oncolysis, cytokine production, enhanced immune response
Reovirus targeting cancer stem cells in BC	Reovirus	Targets CSCs (CD24 − CD44 +), induces apoptosis in CSCs and non-CSCs

dsRNA viruses containing Reovirus are the most prominent viruses in the category [65]. The primary mechanism of reovirus oncolysis of cancer cells has been shown to occur through apoptosis with autophagy during this process in specific cancers [70].

Studies have shown that combining reassortant reovirus with topoisomerase inhibitors can enhance the virus's infectivity and cytotoxicity in TNBC cells. Additionally, this combination therapy activates DNA damage response pathways and induces the production of type III interferon, which negatively affects cancer cell proliferation. These findings highlight the potential of using reovirus in combination with small molecules for more effective treatment of triple-negative BC [71]. A study showed that combining oncolytic Reovirus with PD-1 blockade enhanced the efficacy of BC treatment. In vitro, Reovirus induced oncolysis, cytokine production, and upregulated PD-L1 expression in tumor cells. In vivo, Reovirus significantly reduced tumor burden and increased survival in the EMT6 mouse model of BC, with further enhancement observed when combined with PD-1 blockade. This combination also triggered a systemic anti-tumor immune response, including increased IFN-γ producing CD8 + T cells, demonstrating the potential of Reovirus and PD-1 blockade as an effective immunotherapeutic strategy for BC [72]. A study revealed that oncolytic reovirus effectively reduces primary BC tumors xenografted in immunocompromised mice and targets cancer stem cells (CSCs). CD24 − CD44 + markers and aldehyde dehydrogenase activity identified CSCs with similar reovirus sensitivity as non-CSCs. Both populations underwent apoptosis following reovirus treatment, with comparable Ras-mediated susceptibility. These findings highlight the potential of reovirus to reduce tumors and target CSCs, offering a promising therapeutic strategy for BC [73] (Table 2).

Advantages and challenges of using OVs in BC treatment

OVs emerge as a promising treatment, highlighting advantages over traditional approaches plagued by limitations, side effects, and the risk of recurrence. Recent clinical trials have demonstrated OV’s ability to initiate lytic procedures, effectively annihilating cancer cells resistant to current therapies [74, 75].

OVs have several critical advantages, including: (1) Malignant Cell Susceptibility to Infections: Because of antiviral weaknesses, OVs can infect cancer cells; (2) Genetic Engineering Enhancements: Several components can be introduced to cancer cells to weaken and eradicate them more effectively; and (3) Activation of the Immune Response: OVs cause cancer cells to burst, releasing antigens that stimulate the immune system [43].

OVs are challenging to pursue; the adverse effects vary depending on the OV type, target cells, cancer location, and patient health. Attacks on healthy cells are more frequent, increasing the chance of infection [43]. The challenges in OVs can be addressed by (1) Toxicity and Tumor-Killing potency: Developing OVs with improved tumor-killing capabilities is critical for obtaining significant anti-tumor effectiveness with low viral doses; and (2) Efficient Virus Delivery to Target malignancies: One key challenge is overcoming obstacles in delivering viruses to metastasized cancers. Local/regional delivery is restricted for metastatic malignancies, while systemic administration encounters hurdles such as difficulty bridging tumor vasculature and viral neutralization by serum factors [64].

Clinical trials

An overview of gene therapy

It took a century of challenges and progress before the first clinical trial in gene therapy was initiated. Wilhelm Johannsen, a Danish botanist, introduced the concept of the "gene" in the early twentieth century to describe the unit of heredity that transmits traits from parents to offspring [76, 77]. In 1953, Francis Crick and James Watson discovered that DNA is composed of double helices, providing the physical basis for genes and heredity, which laid the foundation for molecular genetics and opened the door to gene therapy [78].

Today, the global landscape of gene therapy clinical trials exceeds 2400, with viral vectors predominating over non-viral ones [79]. Among viral vectors, adenoviruses lead, followed by retroviruses. In 2003, the Chinese State Food and Drug Administration (SFDA) approved the first gene therapy product, Gendicine, an adenovirus vector (Adv-5) expressing the P53 gene to treat head and neck squamous cell carcinoma (HNSCC). However, in 2005, the SFDA banned Oncorine, a modified adenovirus vector capable of replicating in cancer cells with TP53 mutation, inducing cell death [80]. Other significant milestones include the approval of Neovasculgen by the Russian Ministry of Health in 2011, a plasmid vector containing the vascular endothelial growth factor (VEGF) gene to treat peripheral arterial disease. In 2012, the European Union authorized the 5-year use of Alipogene Tiparvovec to treat lipoprotein lipase deficiency [81]. This was followed by the EU’s approval in 2015 for Talimogene laherparepvec, a herpesvirus vector, for treating metastatic melanoma. Additionally, in 2017, the FDA approved Axicabtagene ciloleucel for relapsed or refractory large B-cell lymphoma, and Voretigene neparvovec-rzyl, a recombinant adeno-associated virus (AAV2) vector expressing the RPE65 gene for progressive vision loss due to a proven biallelic mutation [82].

Gene therapy has also been explored in clinical studies for metastatic BC. In 2007, Rexin-G was administered to a 74-year-old woman with stage T3N2 infiltrating ductal carcinoma of the breast after her disease became chemoresistant. The tumors regressed, allowing for the surgical removal of a fibrotic mass, which showed evidence of apoptosis and tumor-infiltrating CD8 + T-cells, a good prognostic signal [83].

Over three-quarters of gene therapy clinical trials are classified as Phase I or I/II, accounting for 77.7% of all trials, with Phase II studies representing 17.1% and Phase II/III and III trials comprising 4.8%. The proportion of Phase II, II/III, and III trials has steadily increased, reflecting the continual advancements bringing gene therapy closer to routine clinical implementation [84].

Nadofaragene firadenovec, a replication-deficient adenovirus delivering human interferon alfa-2b cDNA, was evaluated in a phase 3, single-arm, open-label clinical trial for patients with BCG-unresponsive non-muscle-invasive bladder cancer. The study reported a 53.4% complete response rate within 3 months among patients with carcinoma in situ, with 45.5% maintaining response at 12 months. The therapy demonstrated a favorable safety profile, with no treatment-related deaths and minimal grade 3 adverse events, positioning it as a promising option for this challenging condition [85].

Gene therapy clinical trials account for 65% of all global trials, targeting cancers such as lung, gynecological, skin, and hematological malignancies, with most trials conducted between 2004 and 2017 [84]. Strategies include tumor suppressor gene therapy, particularly the p53 gene, and immunotherapy approaches such as vaccines with engineered tumor cells and viral vectors encoding tumor antigens. CAR T-cell therapy has successfully treated acute lymphoblastic leukemia, with patients achieving complete remission. OVT, which uses viruses to target and destroy tumor cells while stimulating immune responses, is also being explored. Some trials combine gene therapy with chemotherapy or radiotherapy [84].

However, there is limited data on the use of gene therapy for BC compared to other cancer types, such as leukemia or melanoma [86]. This lack of research on gene therapy approaches for BC could be attributed to the complexity and heterogeneity of the disease [86], as well as challenges in effectively targeting specific genetic mutations using gene therapy [87].

Challenges in clinical trials of gene therapy

Despite its therapeutic benefits, gene therapy has hurdles and restrictions. Most gene therapy options provide patients with only temporary advantages, and permanent treatments may include accompanying hazards. Unexpected adverse effects are possible outcomes, and there is a scarcity of long-term evidence on the impact of gene therapy approaches on patients. Overcoming extracellular and intracellular barriers is a big issue, as foreign genes entering the human biological system are identified as external pathogens and removed by the reticuloendothelial system (RES) before reaching the target cell. The procedure is further complicated by intracellular hurdles such as endosomal trapping, lysosomal breakdown, and crossing the nuclear membrane to release DNA or cytoplasmic RNA [21, 88].

Vectors need precise control over the insertion position of genes into the genome; putting genes in quiet genome areas renders them nonfunctional while disrupting or activating adjacent genes can induce cancer [82]. Viral vectors provide additional issues since repeated injections may develop antibodies that kill the vector in subsequent doses. Individuals are unfamiliar with the viral vector, which adds to the complexity. Furthermore, the high cost and demand for modern facilities and qualified personnel substantially restrict the general deployment of gene therapy procedures [21].

Future perspective

As a cutting-edge therapeutic strategy, gene therapy is a promising avenue for safe, highly successful, and efficient BC treatment gene therapy with traditional cancer treatment tactics. The achievement provides gene ENT [89]. Delivery technology advances allow for precise gene expression targeting specific tissues and organs, aligning therapy as a feasible alternative for neoplastic illnesses, perhaps becoming a first-line therapeutic strategy [90]. The variety of gene therapy techniques has grown dramatically, with initial emphasis on uncommon illnesses linked with unfavorable monogenetic abnormalities. However, further study has extended the use of innovative gene therapy procedures to cover progressive and chronic diseases, including heart failure, neurodegeneration, metabolic disorders, and cancer [91, 92].

Improved delivery methods and targeting strategies

Advances in the genetic modification of cancer cells have resulted in more effective therapy options with fewer adverse effects. In addition, the development of effective gene delivery technologies has become critical. Gene delivery techniques are widely classified into viral and non-viral [93]. Viral vectors, commonly used due to their better transfection effectiveness, prevail over non-viral vectors in cancer gene therapy, where increasing the transduction of therapeutic genes into cancer cells is the key focus [94, 95].

Nonviral vectors, such as liposomes—a nanoparticle system of lipid bilayers—have received interest. Cationic, anionic, and neutral liposomes are evaluated for stability, cytotoxicity, transfection efficiency, cellular uptake, and appropriateness as gene carriers for cancer treatment. Cationic liposomes are ideal for the formulation of gene delivery and therapy in BC treatment due to their practical technique of exploiting electrostatic interaction with negatively charged nucleic acids and cell membranes for increased absorption [89].

Combination therapies with existing treatments

"Combination therapy" stands out as a successful strategy for treating human medical conditions, especially BC. Integrating gene therapy with current therapies like chemotherapy or radiotherapy provides good potential for improving therapeutic results in individuals with advanced-stage malignancies [96]. Drug resistance mechanisms include increased efflux of cytotoxins via transporters, enhanced repair/tolerance to DNA damage, more significant anti-apoptotic potential, reduced permeability, and enzymatic deactivation, allowing cancer cells to survive chemotherapy [97]. Gene therapy strategies targeting these resistance systems can play a major role in boosting intracellular drug concentration and, hence, the effectiveness of cytotoxic medicines [98].

A study focused on the synergistic or additive effects of coupling TRAIL gene therapy with chemotherapeutic drugs (doxorubicin, paclitaxel, vinorelbine, gemcitabine, irinotecan, and floxuridine) in several BC cell lines, including those that are resistant to chemotherapy. The combination showed great effectiveness, suggesting gene therapy could overcome chemotherapy resistance [99].

Development of personalized gene therapies based on individual genetic profiles

Recent advancements in personalized medicine entail establishing signs or markers that aid when picking the appropriate people to treat with such therapy and which therapy will be most beneficial for a patient [100]. Genomic reports on several cancer types, including breast, colon, lung, ovarian, and renal malignancies, have been published. They intended to uncover genetic changes potentially targetable or related to treatment resistance, which would enable individualized cancer therapy [101]. The finest example is the studies on the BC genome, which discovered possible targets for particular genetic modifications of BC. Females with mutations in genes associated with DNA repair, such as BRCA1 and BRCA2, had a greater risk of BC [102].

Approximately 5–10% of breast and ovarian cancer cases are thought to be hereditary, with BRCA1 and BRCA2 accounting for 21–40% of these occurrences [103, 104]. Increased understanding of the molecular activities of BRCA1 and BRCA2 has prompted clinical studies evaluating targeted medicines for people who have these genetic abnormalities. Identifying somatic mutations in BC has cleared the door for treatments to target these altered genes, resulting in the quick regulatory approval of numerous medicines widely used in clinical practice [105].

Conclusion

The landscape of breast cancer (BC) treatment is undergoing a significant transformation driven by advancements in gene therapy, with CRISPR/Cas9 technology and oncolytic virotherapy (OVT) at the forefront. These innovations can overcome the limitations of conventional treatments, such as systemic toxicity, resistance, and metastasis, by offering targeted and personalized approaches. CRISPR/Cas9 enables precise genetic corrections in oncogenes like HER2 and MYC, while OVT harnesses genetically engineered viruses to selectively destroy cancer cells and activate immune responses.

Integrating gene therapy with existing modalities, including chemotherapy and immunotherapy, presents a synergistic approach that enhances treatment efficacy and reduces adverse effects. Furthermore, the advent of personalized medicine—guided by genomic profiling—facilitates tailored interventions that directly address patient-specific mutations such as BRCA1 and BRCA2, underscoring the role of gene therapy in advancing precision oncology. Despite these promising developments, challenges persist, particularly in delivery mechanisms, off-target effects, and ethical considerations. Addressing these barriers through continued research, innovation in vector technology, and robust clinical trials is essential for translating gene therapy into standard clinical practice.

In conclusion, the future of BC treatment lies in the convergence of gene therapy, immunotherapy, and personalized medicine. This multifaceted approach promises to improve survival rates and enhance the quality of life for patients by minimizing treatment-related morbidity. As we continue to bridge the gap between scientific discovery and clinical application, gene therapy emerges as a beacon of hope, potentially transforming BC from a life-threatening disease into a manageable condition.

Author contributions

M.S. conceived the original idea for this work and took the lead in writing the manuscript, drafting most of the main content. S.S. contributed to writing the clinical trial section and also assisted with proofreading and reviewing the manuscript for English language and grammar. H.A. took the lead in creating the figures and also supported S.S. in proofreading and grammar review. M.M. assisted M.S. in drafting the section on oncolytic viruses. F.H. helped coordinate the team and assisted the corresponding author with organizational tasks. F.B. supported M.S. in verifying the accuracy of the references. All authors approved the final version of the review for publication.

Data availability

No datasets were generated or analysed during the current study.

Declarations

Competing interests

The authors declare no competing interests.