Gankyrin‐Protein Interactions in GI Cancers: A Novel Target of New Therapeutics

ABSTRACT

Gankyrin (PSMD10) is a 25 kDa oncogenic protein and regulatory subunit of the 26S proteasome, characterized by a sevenfold ankyrin repeat domain. Gankyrin is overexpressed in various malignancies, particularly gastrointestinal (GI) cancers. Gankyrin contributes to tumorigenesis by modulating key signaling pathways and engaging in oncogenic protein–protein interactions with tumor suppressors, including p53 and Rb, thereby promoting cell proliferation, metastasis, and resistance to treatment. Recent advances have shed light on the structural basis of gankyrin's molecular interactions, its potential as a diagnostic and prognostic biomarker, and emerging therapeutic strategies. Together, targeting gankyrin represents a promising strategy for precision oncology in GI cancers.

Summary

• Gankyrin plays a critical role in degrading tumor suppressors.

• Gankyrin regulates the cell cycle through various pathways.

• Interruption of Gankyrin‐protein interactions is promising for cancer drug design.

Abbreviations

AKT

protein kinase B

CDK4

cyclin dependent kinase 4

E2F

E2 promoter‐binding factors

IL‐1β

interleukin‐1 beta

IL‐6

interleukin‐6

IRAK1

interleukin‐1 receptor‐associated kinase 1

JAK‐2

Janus kinase‐2

MDM2

murine double minute 2

NFκB

nuclear Factor kappa light chain enhancer of activated B cells

P

phosphorylation

p53

tumor protein p53

PI3K

phosphoinositide 3 kinase

PTEN

phosphatase and tensin homolog

Rb

retinoblastoma protein

RelA

RELA proto‐oncogene/NFκB subunit p65/transcription factor p65

RhoA

Ras homolog gene family member A

RhoGDI

Rho GDP dissociation inhibitor

ROCK

Rho associated protein kinase

SIRT1

silent information regulator 1

STAT3

signal transducer and activator of transcription 3

1. Introduction

Gankyrin, also called PSMD10, is a novel oncogenic protein first found to be overexpressed in hepatocellular carcinoma (HCC) [1, 2]. It functions as a component of the 26S proteasome regulatory complex for protein degradation [1]. Gankyrin is frequently overexpressed in multiple cancer types, including HCC, pancreatic cancer, and colorectal cancer (CRC) [2]. By modulating multiple cell signaling pathways, its overexpression contributes to tumor progression, metastasis, and immune evasion.

Among its most well‐characterized functions is the regulation of key tumor suppressor proteins, particularly p53 and retinoblastoma (Rb). Gankyrin promotes the degradation of tumor suppressors p53 and Rb, and functionally disables Rb by direct binding. This leads to uncontrolled cell cycle progression [3, 4]. In combination with its influence on other signaling networks, these activities enhance invasive behavior, support metastatic spread, and suppress cell death. Thus, targeting gankyrin may be a promising strategy for cancer treatments [1]. This review will discuss gankyirin's protein interactions, its oncogenic roles, current therapeutic approaches, and future potential as a novel therapeutic target.

2. Protein–Protein Interactions (PPIs) in Cancer

Cells are constantly exposed to DNA damage caused by intrinsic and extrinsic factors. To maintain genomic stability, DNA damage responses are activated to promote cell cycle arrest, DNA repair, and apoptosis [5]. These protective mechanisms involve several key regulators, including tumor suppressor proteins such as p53 and Rb. In addition, multiple signaling pathways play essential roles, including RhoA/ROCK, PI3K/Akt, NF‐κB/RelA, IL‐6/signal transducer and activator of transcription 3 (STAT3), interleukin‐1 beta (IL‐1β)/interleukin‐1 receptor‐associated kinase 1 (IRAK‐1), and Wnt/β‐catenin (Figure 1). These signaling pathways are highly interconnected, which highlights the complexity of the regulatory network and underscores the central role of gankyrin in cancer progression.

Figure 1.

Gankyrin functions as a hub, linking multiple signaling pathways such as Wnt/β‐catenin, RhoA/ROCK, PI3K/Akt, NF‐κB/RelA, IL‐1β/IRAK‐1, and IL‐6/STAT3, driving tumorigenesis. Gankyrin's central role in these interconnected signaling networks emphasizes its contribution to the complexity and progression of cancer. PDB ID of gankyrin: 1qym. Other structures and the binding complexes were generated using AlphaFold 3 as monomeric proteins [6].

2.1. Regulation of Tumor Suppressors

Gankyrin engages in several critical protein interactions that contribute to the hallmarks of cancer, particularly through its regulation of the tumor suppressor proteins p53 and Rb. Both proteins play an essential role in cell cycle regulation. Disruption of their activity is a key mechanism through which gankyrin exerts its oncogenic effects [1].

p53 is a crucial cell cycle regulator that is activated in response to DNA damage [5]. Under normal conditions, it prevents the proliferation of mutated cells by inducing cell cycle arrest or triggering apoptosis when damage is irreparable [7]. When p53 function is impaired, cells accumulate mutations, evade apoptosis, and acquire malignant potential. Gankyrin contributes to this deregulation by binding to MDM2, an E3 ubiquitin ligase responsible for p53 degradation (Figure 2) [2]. This leads to apoptosis resistance, cell proliferation, and the promotion of invasion and metastasis.

Figure 2.

Gankyrin contributes to oncogenesis by disrupting tumor suppressor proteins, p53 and Rb. These proteins are essential for controlling cell cycle arrest and apoptosis. It enhances p53 degradation through MDM2 interaction and drives uncontrolled cell proliferation by facilitating Rb phosphorylation and E2F release.

Rb is another pivotal regulator of the cell cycle. In its unphosphorylated state, Rb binds to E2F transcription factors and inhibits DNA replication [8]. This serves as a critical checkpoint to restrict uncontrolled proliferation. Gankyrin disrupts this regulatory mechanism by binding to Rb and CDK4 [9]. This interaction leads to Rb phosphorylation and the release of E2F transcription factor that drives cell cycle progression, specifically from G1 phase into the S phase (Figure 2) [9, 10]. As a result, gankyrin drives unchecked cell division and contributes to tumor growth.

2.2. RhoA/ROCK Signaling Pathway

Gankyrin plays an important role in the Ras‐driven oncogenesis by modulating both the RhoA/ROCK and PI3K/Akt signaling pathways. Gankyrin expression is upregulated upon Ras activation, which enhances the interaction between RhoA (Ras homolog family member A) and RhoGDI (a GDP dissociation inhibitor) [11]. This interaction alters the normal regulation of cytoskeletal dynamics and disrupts apoptosis signaling. Inhibition of the downstream effector ROCK contributes to prolonged activation of Akt, a serine/threonine kinase that promotes cell survival and growth [11]. Akt activation plays a role in tumor progression. Additionally, Akt inhibits apoptosis and is often activated through mutations or deletions of the tumor suppressor gene PTEN [11]. Under normal conditions, PTEN dephosphorylates PIP3, serving as a negative regulator of the PI3K/Akt pathway [12]. Inactivation of PTEN contributes to the hyperactivation of Akt and drives tumorigenesis [11]. In this context, gankyrin's ability to prolong Akt signaling through ROCK inhibition may act synergistically with PTEN loss. Together, these alterations promote uncontrolled proliferation, enhanced survival, and cancer progression.

2.3. NF‐κB/RelA Signaling Pathway

The NF‐κB/RelA signaling pathway plays a central role in immune regulation, inflammation, cell survival, and apoptosis. Structurally, gankyrin shares structural similarity with the IκB family of inhibitory proteins, as both contain seven ankyrin repeat motifs. This similarity enables gankyrin to interact with components of the NF‐κB pathway [13]. NF‐κB/RelA proteins exist as dimers at the resting state and are sequestered in the cytoplasm by inhibitory proteins like IκBα, a prototypical member of the IκBs family of inhibitory proteins [13]. Upon activation, IκBα is phosphorylated and then degraded in the proteasome, releasing NF‐κB dimer to translocate into the nucleus [14]. Once in the nucleus, NF‐κB's function is further regulated. Acetylation of RelA by transcriptional coactivators, such as p300, CREB‐binding protein (CBP), and PCAF, enhances its transcriptional activity [15]. Gankyrin modulates this process by interacting with SIRT1, a class III histone deacetylase. Through this interaction, gankyrin promotes the deacetylation of nuclear RelA, thereby attenuating NFκB‐mediated transcription (Figure 1) [15]. Through this mechanism, gankyrin acts as a negative regulator of NF‐κB signaling, linking its role in immune modulation to anti‐apoptotic and tumor‐promoting functions.

2.4. IL‐6/STAT3 Signaling Pathway

The IL‐6/STAT3 signaling pathway is a key inflammatory pathway and regulator of the immune response. Interleukin‐6 (IL‐6) is a cytokine that can activate Janus kinase 2 (JAK‐2) and STAT3 [16]. Gankyrin has been shown to increase IL‐6 levels, which promotes JAK‐2‐dependent phosphorylation of STAT3 [17]. After phosphorylation, STAT3 dimerizes, translocates to the nucleus, and binds to specific DNA response elements in the promoters of target genes, such as cyclin D1 and vascular endothelial growth factor [18]. This cascade forms a positive feedback loop, as overactivated STAT3 persistently induces IL‐6 expression and thus activates IL‐6/STAT3 signaling pathway. Persistent activation of this loop contributes to a pro‐tumorigenic environment by promoting uncontrolled cell proliferation, resistance to apoptosis, increased invasive potential, and chronic inflammation [17].

2.5. IL‐1β/IRAK‐1 Signaling Pathway

Another key inflammatory pathway involved in cancer is the IL‐1β/IRAK‐1 signaling pathway. Upon stimulation, inflammatory cytokine IL‐1β binds to the IL‐1R receptor, triggering downstream signaling. This leads to the recruitment of the adapter protein myeloid differentiation primary response gene 88 (MyD88), along with IL‐1 receptor‐associated kinase‐1 and kinase‐4 (IRAK‐1 and IRAK‐4) to the IL‐1 receptor complex [1]. IRAK‐4 phosphorylates and activates IRAK‐1, which subsequently undergoes autophosphorylation and interacts with tumor necrosis factor receptor‐associated factor 6 (TRAF6) to trigger a broader inflammatory response [10]. This cascade ultimately leads to the activation of transcription factors, such as NF‐κB and AP‐1. These factors translocate into the nucleus and promote the expression of pro‐inflammatory genes, including IL‐6, IL‐8, and TNF‐α [19]. Importantly, this pathway also contributes to the transcriptional upregulation of gankyrin. Activation of IL‐1β/IRAK‐1 signaling promotes the binding of the nuclear factor (NF‐Y) complex to the gankyrin promoter. This recruits transcriptional coactivators, such as E1A‐binding protein p300 and CBP, leading to increased gankyrin expression [2]. Elevated gankyrin levels can further amplify inflammatory signaling and support tumor‐promoting processes.

2.6. Wnt/β‐Catenin Signaling Pathway

Wnt/β‐catenin signaling pathway plays a significant role in regulating physiological homeostasis, and its dysregulation is strongly associated with tumorigenesis [20]. β‐Catenin is an essential effector of this pathway, functioning both as a transcription co‐activator and an adapter protein at adherent junctions [21]. Together with α‐catenin, it binds to the cytoplasmic domain of E‐cadherin and contributes to cell‐cell adhesion and structural organization of tissue architecture [18]. In the absence of Wnt ligands, β‐catenin is continuously targeted for degradation through the ubiquitin‐proteasome system [21]. The degradation is mediated by β‐Catenin destruction complex, consisting of adenomatous polyposis coli, Axin‐1/2, glycogen synthase kinase 3 (GSK3β), casein kinase 1α (CK1α), and E3 ubiquitin ligase β‐TrCP2 [20].

Genetic mutations of key Wnt components or activation by Wnt ligands can inhibit the β‐catenin destruction complex. This leads to the accumulation of β‐catenin in the cytoplasm [21]. Eventually, β‐catenin translocates into the nucleus, where it binds to T‐cell factor/lymphoid enhancer factor (TCF/LEF) family transcription factors and co‐regulators [20, 21]. This subsequently drives the transcription of various oncogenic genes, including Jun, c‐Myc, and Cyclin D1 [1].

Notably, there is a positive feedback loop between β‐catenin signaling and gankyrin expression [2]. β‐catenin enhances gankyrin expression, and gankyrin, in turn, promotes further activation of Wnt/β‐catenin signaling. This feedback loop amplifies Wnt/β‐catenin pathway signaling and promotes the transcription of oncogenes, facilitating uncontrolled cell proliferation and tumor progression.

3. Structure and PPIs

The ankyrin repeats are conserved structural motifs found in a wide range of proteins across different species. Each repeat is composed of 2 alpha helices separated by a loop, and the seven repeats are arranged side‐by‐side to form a slightly curved solenoid (Figure 3A) [22]. This curved solenoid forms a long concave at the outer surface and a shallow groove at the inner face (Figure 3).

Figure 3.

The structure of gankyrin without a binding protein (PDB ID: 1qym). Helix is shown in red, while the loop is shown in green. (A) Gankyrin's secondary structure is shown beneath an 80% transparent surface view, rendering both the surface and internal structures visible. Gankyrin forms a concave structure, comprising seven ankyrin repeats, ank 1–7. Each repeat forms a helix‐loop‐helix structure. (B) Gankyrin's opaque surface view highlights the protein binding site at the inner surface. The inner concave surface (dotted) is responsible for interacting with proteins.

The primary function of ankyrin repeats is to support PPIs. A commonly observed sequence within the core of ankyrin repeats is amino acids TPLH [23, 24]. These amino acids play a key role in stabilizing the fold and promoting the tight packing with neighboring repeats. While the core structure of each repeat is conserved, the outer surface shows variations in sequence and distinct structural patterns. This leads to various binding specificities of the repeats, which form modular arrangements for protein binding. Repeats 3 and 4 are known to interact with CDK4 [25], while repeats 5 and 6 are involved in binding MDM2 [26] and Rb [25]. The modular arrangement allows gankyrin to engage with multiple regulatory partners simultaneously. Through these interactions, gankyrin participates in the control of protein degradation and cell cycle progression, playing an important role in cellular regulation and cancer biology.

Structures of gankyrin binding complexes have revealed interactions on both the inner and outer surfaces of the protein. In the complex of gankyrin and S6 ATPase C‐terminus (Figure 4A) [27], the latter binds along the inner surface, engaging primarily with ankyrin repeats 2 through 6. The interaction is characterized by complementary charged residues: the negatively charged regions of S6 ATPase align with positively charged patches on gankyrin. This region of gankyrin is also involved in binding other important partners, such as the Rb protein and CDK4. This indicates that the concave face of repeats 2 through 6 is a critical interaction hub for its role in regulating the cell cycle and protein degradation.

Figure 4.

The structures of gankyrin with binding proteins. (A) The crystal structure of gankyrin bound with the C‐terminus of S6 ATPase (PDB ID: 2dvw). (B) The crystal structure of gankyrin bound with a single‐chain variable antibody fragment, F5 (PDB ID: 4nik). The secondary structures are shown beneath an 80% transparent surface view.

The outer surface has not been established to be critical for protein binding physiologically. The single‐chain variable antibody fragment, F5, binds to the outer surface formed by ankyrin repeats 3 to 6 (Figure 4B) [28]. F5 was generated through phage display using a biased synthetic antibody library and thus cannot represent the natural binding partners of gankyrin.

4. Gankyrin as a Biomarker and Therapeutic Target

Studies have shown that gankyrin overexpression is associated with poor outcomes in multiple cancer types. A meta‐analysis has demonstrated its prognostic value, particularly among Asian patients with gastrointestinal (GI) cancers [10, 29]. In HCC, gankyrin expression increases throughout the multistep development of hepatocarcinogenesis. Higher levels of gankyrin correlate with poor outcomes, including vascular invasion, tumor thrombus formation, and distant metastasis [30, 31, 32]. In esophageal squamous cell carcinoma (ESCC), elevated gankyrin expression is associated with advanced clinical stages, lymphatic invasion, and shorter overall survival [33, 34]. In gastric cancer, higher gankyrin levels correlate with larger tumor size, higher risk of metastasis, resistance to chemotherapy, and poor prognosis [4, 35, 36, 37]. Similarly, CRC patients with high gankyrin expression exhibit more aggressive disease with liver metastasis and worse prognosis [38, 39, 40]. In pancreatic cancer, gankyrin is also markedly regulated and correlated with increased tumor proliferation [41].

4.1. The Role of Gankyrin in Cancer

4.1.1. Cell Proliferation

In HCC cell lines HepG2, silencing gankyrin significantly reduces cell proliferation and tumor growth [31]. Gankyrin drives proliferation through several oncogenic pathways. Among the oncogenic pathways, the STAT3/IL‐6 signaling pathway is important for the maintenance of cancer stem cells [42]. In gastric cancer, knockdown of gankyrin could increase chemotherapy sensitivity and inhibit proliferation. This effect is mediated through disruption of the PI3K/AKT signaling by regulating cell survival and growth [4, 37]. In pancreatic cancer, gankyrin knockdown suppresses proliferation by altering the expression of cyclin A, D1, and E. It also restores the functions of tumor suppressors p53 and Rb [41].

4.1.2. Regulation of Apoptosis

In HCC, histone deacetylase inhibitors like LBH589 (panobinostat) could inhibit gankyrin, thus inducing cell cycle arrest and promoting apoptosis [43]. In gastric cancer, downregulation of gankyrin potentiates apoptosis and enhances chemotherapy‐induced apoptosis, emphasizing its role in tumor cell survival and resistance to therapy [4, 37].

4.1.3. Influence on Metastasis

In HCC, gankyrin silencing significantly reduces metastasis and invasion [31, 32]. In ESCC, gankyrin downregulation suppresses cell invasion and lymphatic metastasis [33, 34]. A similar effect is observed in CRC, where gankyrin promotes liver metastasis through upregulation of IL‐8 and cyclin D1 signaling. Both pathways are closely associated with enhanced migration and invasion [40, 44, 45].

4.2. Gankyrin Function in GI Cancers

4.2.1. HCC

HCC remains one of the most lethal GI malignancies, often diagnosed at an advanced stage with limited effective therapeutic options [46, 47]. Gankyrin expression increases progressively from cirrhotic liver tissue to overt carcinoma [30]. In HCC patients, its overexpression is correlated with aggressive phenotypes, such as vascular invasion, portal vein tumor thrombus formation, and distant metastasis [30, 32]. Elevated gankyrin level in the tumor microenvironment is associated with shorter progression‐free survival in HCC patients treated with sorafenib, suggesting its potential as a predictive biomarker [42].

Gankyrin could activate IL‐6/STAT3 signaling, which enhances the expression of cancer stem cell markers, such as EpCAM and Bmi1. This contributes to tumor initiation and resistance to therapy [42]. Gankyrin also influences the self‐renewal capacity of hepatic progenitor‐like cells by regulating hepatocyte nuclear factor 4α (HNF4α) via proteasome‐dependent degradation [48].

Recent studies have identified SMARCA4, a core subunit of the SWI/SNF chromatin remodeling complex, as a transcriptional activator of gankyrin in HCC. SMARCA4 is frequently overexpressed in HCC and binds to a distal enhancer upstream of the IRAK‐1 gene. Through its chromatin remodeling activity, SMARCA4 promotes histone acetylation and the recruitment of transcriptional machinery at the IRAK‐1 enhancer, leading to IRAK‐1 expression upregulation. This subsequently upregulates gankyrin and AKR1B10, forming a SMARCA4–IRAK‐1–gankyrin axis that drives carcinogenesis. This epigenetic regulation demonstrates a novel mechanism of gankyrin upregulation in liver cancer [49].

Furthermore, gankyrin interacts with ATG7 to upregulate autophagy in response to chemotherapy and nutrient deprivation [50]. In addition, gankyrin allows tumor cells to survive during oxidative stress through the Nrf2 feedback loop [51]. Pharmacologic inhibition with HDAC inhibitors such as panobinostat (LBH589) could disrupt the gankyrin/STAT3/AKT axis, resulting in increased apoptosis and reduced tumor growth [43].

4.2.2. ESCC

ESCC is a major histologic subtype of esophageal cancer. Gankyrin is significantly overexpressed in ESCC tissues and cell lines compared to normal esophageal epithelium. High gankyrin expression correlates with poor clinical outcomes, including advanced T stage, lymph node metastasis, and shorter overall survival [33, 34]. In addition, primarily through the PI3K/AKT signaling pathway. Silencing gankyrin using shRNA or small interfering RNA (siRNA) in invasive ESCC cells significantly suppresses cell invasion and tumor formation [33, 34]. Given its clinical association and functional impact on tumor aggressiveness, gankyrin represents a promising prognostic biomarker and therapeutic target in ESCC.

4.2.3. Gastric Cancer

Gastric cancer displays considerable molecular and histological heterogeneity. Accumulating evidence shows that gankyrin overexpression is correlated with aggressive disease and poor prognosis. A single‐nucleotide polymorphism (SNP rs111638916) at the 3′ untranslated region of the gankyrin gene is related to the dysregulation of gankyrin expression. This variant upregulates gankyrin expression via altered miR‐505 binding, increasing metastatic potential and tumor burden in patients with GA or AA genotypes [35]. In a xenograft model, knockdown of gankyrin in Helicobacter pylori‐infected AGS cells significantly reduced tumor growth and TNF‐α levels, while restoring NF‐κB, pRb, and p53 expression [52].

In addition, gankyrin is involved in Epstein–Barr virus (EBV)‐associated gastric cancer. EBNA1, a key EBV nuclear antigen, transcriptionally upregulates gankyrin, which in turn increases expression of p53‐inhibitory genes, such as MDM2, MDM4, and PSMD10. This results in functional inactivation of p53 and enables tumor cells to evade apoptosis. Inhibition of USP7, a deubiquitinase that stabilizes both MDM2 and gankyrin, leads to p53 accumulation and apoptosis [53].

Gankyrin regulates cell cycle progression by upregulating proteins, such as cyclin D1 and cyclin E. In addition, it enhances the expression of drug efflux transporters, which lower intracellular concentrations of cytotoxic agents like vincristine and adriamycin [37]. Gankyrin silencing sensitizes gastric cancer cells to 5‐fluorouracil and cisplatin, through suppression of the PI3K/AKT pathway and reactivation of apoptotic signaling [4].

4.2.4. CRC

In CRC, elevated gankyrin expression is associated with advanced tumor stage, lymphatic invasion, and liver metastasis [38, 39, 40]. Further studies showed that gankyrin promotes migration and invasion by upregulating IL‐8 and cyclin D1. Loss of cyclin D1 decreases gankyrin‐induced migration, while the addition of exogenous IL‐8 restores the effect [40].

Qin et al. [44] found that gankyrin could enhance mTORC1 signaling, which promotes protein synthesis and cell proliferation. Additionally, gankyrin activates the PI3K/GSK‐3β/β‐catenin pathway, a central regulator of epithelial to mesenchymal transition and tumor aggressiveness [45]. In colitis‐associated cancer, gankyrin expression is elevated in tumor cells and immune cells. It binds to SHP‐1 and enhances STAT3 activation, leading to elevated TNF‐α and IL‐7 production [54].

4.2.5. Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) remains an aggressive disease with a poor prognosis. Gankyrin expression is significantly upregulated in tumor tissues compared to adjacent normal pancreas [41]. It promotes tumor cell proliferation by regulating key cyclins (A, D1, E) and cyclin‐dependent kinases (CDK2, CDK4). Gankyrin also decreases tumor suppressors, such as p27, Rb, and p53, further facilitating unregulated cell proliferation. In PDAC, gankyrin could influence the G1/S transition, a crucial checkpoint in the cell cycle.

5. Strategies

The role of gankyrin in cell cycle regulation, apoptosis evasion, and proteasomal degradation in GI cancers makes it a promising target. This section reviews current strategies for targeting gankyrin, including small‐molecule inhibitors, peptide‐based approaches, and RNA interference (RNAi).

5.1. Small‐Molecule Inhibitors

Small‐molecule inhibitors are designed to interfere with critical PPIs mediated by gankyrin's ankyrin repeat domains. One of the earliest molecules reported is cjoc42, developed through a structure‐guided approach based on the structural configuration of ankyrin motifs [55]. The interaction between gankyrin and the C‐terminal of Rpt3 is disrupted by cjoc42. The disruption results in the stabilization and reactivation of tumor suppressor p53, thereby enhancing cellular sensitivity to DNA damage. Kanabar et al. [56] developed cjoc42 derivatives such as 51c and 51d, which showed improved ability to destabilize gankyrin and restore tumor suppressor levels. In a related study, 2,5‐substituted pyrimidines were synthesized as gankyrin inhibitors. Compounds 188 and 193 showed strong binding affinity, disrupted proteasomal degradation, and inhibited tumor cell growth in breast cancer and lung cancer [57]. A near‐infrared screening approach identified a covalent peptoid that binds gankyrin even in complex lysates, offering a valuable tool for further functional studies [58].

However, there are several limitations, such as the flat and extended binding surfaces of ankyrin repeat proteins often lack well‐defined hydrophobic pockets for high‐affinity binding by conventional small molecules. In addition, most compounds require further optimization to improve pharmacokinetics and bioavailability, to increase potency and selectivity, and to minimize the off‐target effects.

5.2. Peptide‐Based Inhibitors

Peptide‐based inhibitors are designed to mimic native gankyrin‐binding domains to block their oncogenic interactions. Structural analysis has identified a druggable pocket on gankyrin. A peptide‐doxorubicin combination targeting this region was shown to reduce cell proliferation and enhance drug sensitivity [59]. In another study, Gandhi et al. developed a synthetic peptide that interferes with the gankyrin–MDM2 complex. The peptide binds MDM2 while simultaneously blocking gankyrin's ankyrin domain [60].

Alternative efforts have focused on synthetic protein scaffolds. Chapman and McNaught applied shape‐complementary protein libraries to engineer gankyrin‐binding proteins [61]. While initial constructs showed only micromolar affinity, further optimization produced GBP7.19 with nanomolar binding (K _d  ≈ 21 nM). GBP7.19 could effectively increase p53 levels by blocking gankyrin‐mediated degradation [62].

However, peptide and protein‐based therapeutics face significant challenges with clinical translation. As these macromolecules have poor membrane permeability, one major barrier is delivery. Due to rapid proteolytic degradation, the in vivo stability is limited. Scientists are focusing on chemical modifications such as cyclization or D‐amino acid substitution to address these issues.

5.3. RNAi Approaches

RNAi provides a direct approach to reducing gankyrin expression at the mRNA level. siRNAs induce post‐transcriptional gene silencing by promoting the degradation of target transcripts. In vitro studies using adenoviral vectors to deliver gankyrin‐targeting siRNA in HCC cell lines (e.g., HepG2, HuH‐7, SMMC‐7721) resulted in over 80% knockdown of gankyrin expression [63]. This knockdown significantly inhibited cell proliferation, migration, and invasion, and induced cell cycle arrest. Mechanistically, these effects were associated with dephosphorylation of Rb and suppression of E2F‐1 activity, both of which are critical for G1 to S phase transition in the cell cycle process. In xenograft models, siRNA delivery led to significant tumor growth inhibition. Notably, siRNA had minimal effect on normal hepatocytes, suggesting a degree of tumor selectivity. These findings show the therapeutic promise of RNAi‐based therapeutic potential in cancers targeting gankyrin overexpression.

Beyond siRNAs, other oligonucleotide approaches have been developed, including antisense oligonucleotides (ASOs) and microRNA mimics. For instance, miR‐605 and miR‐214 directly target gankyrin mRNA and have been shown to suppress tumor proliferation in intrahepatic cholangiocarcinoma and multiple myeloma, respectively [64, 65].

However, naked siRNAs are rapidly degraded in circulation and may elicit immune responses. To overcome these issues, researchers have developed strategies, such as lipid nanoparticles, ligand conjugation, and chemical modifications (e.g., 2′‐O‐methylation, phosphorothioate backbones). These strategies are expected to improve stability, targeting efficiency, and safety of RNA‐based approaches.

6. Conclusion and Perspectives

As a key oncogenic regulator in many GI malignancies, gankyrin exerts its oncogenic effects through interaction with multiple molecular partners via its ankyrin repeat domains, modulating key signaling pathways. It not only promotes tumor initiation and proliferation but also facilitates immune evasion, cancer stemness, and chemoresistance. Both genetic and pharmacologic approaches, such as siRNA, ASOs, synthetic peptides, and small molecule inhibitors, have shown preclinical efficacy in disrupting gankyrin function and restoring tumor suppressor activity.

In addition to its therapeutic potential, gankyrin may serve as a useful biomarker. Its high tumor‐specific expression makes it a potential marker for targeted therapies and therapeutic response prediction. The emerging interest in gankyrin‐regulating microRNAs further suggests potential for epigenetic modulation and combination therapies.

Despite these promising findings, translating gankyrin‐targeted strategies into clinical use remains challenging. Key obstacles include the structural complexity of gankyrin's interaction interfaces, delivery limitations for peptide and RNA‐based therapeutics, and inter‐tumor heterogeneity. Further investigation is needed to address these issues. Comprehensive molecular characterization of gankyrin's role across tumor subtypes, combined with advances in drug design and biomarker discovery, will be essential for unlocking its full therapeutic potential.

In summary, gankyrin is a promising therapeutic target in GI cancers. Further research on its regulatory functions, structural biology, and tumor‐specific roles will be critical in driving the development of gankyrin‐based strategies for precision oncology.

Author Contributions

Shuang Li, Zhe‐Sheng Chen, and Shanzhi Wang designed the topic and overall structure. Shuang Li and Yuky Lam conducted the literature search and prepared the manuscript. Aaron Muth, Zhe‐Sheng Chen, and Shanzhi Wang provided conceptual guidance and critical review.

Ethics Statement

The authors have nothing to report.

Conflicts of Interest

The authors declare no conflicts of interest.

Li S., Lam Y., Muth A., Chen Z.‐S., and Wang S., “Gankyrin‐Protein Interactions in GI Cancers: A Novel Target of New Therapeutics,” Chronic Diseases and Translational Medicine 11 (2025): 269‐278, 10.1002/cdt3.70025.

Data Availability Statement

The authors have nothing to report.