ob/ob obese mice promote tumorigenesis of endometrial cancer associated with Pten deficiency

Abstract

Obesity refers to the condition of being overweight due to abnormal fat accumulation and is highly associated with development of various cancers. Endometrial cancer is the most diagnosed gynecologic cancer. Obesity is a strong risk factor for endometrial cancer. However, etiological and pathophysiological effects of obesity on endometrial cancer have not been fully understood. To determine the effect of obesity on tumorigenesis in endometrial cancer, we examined the effect of obesity on tumorigenesis using genetically engineered mouse models, including an obesity model (ob/ob), an endometrial cancer model (Pgr^cre/+Pten^f/f; Pten^d/d), and an endometrial cancer with obesity model (Pgr^cre/+Pten^f/fob/ob; Pten^d/dob/ob). Histopathological analysis was performed on the uteri of the three groups during tumorigenesis. From 1.5-months of age, the body and uterine weight of Pten^d/dob/ob mice were significantly higher than that of the Pten^d/d mice. Pten^d/dob/ob mice had higher tumor grade with myometrial invasion at 1.5 and 2 months than Pten^d/d mice. The levels of phospho-Histone H3, proliferation marker, and phospho-STAT3 were significantly increased in endometrial cancer of Pten^d/dob/ob mice compared to Pten^d/d mice. Our results suggest that obesity accelerates the progression of endometrial cancer associated with Pten mutation.

Introduction

Endometrial cancer is one of the most common gynecologic malignancies. In the United States, approximately 68,000 cases are diagnosed each year (Sung, et al. 2021). In contrast to many other reproductive cancers, endometrial cancer incidence is rising across all age groups, with a 14-fold increase in incidence rates in women younger than 45 years old and a greater than 50-fold increase in women 45 to 54 years old from 1988 to 2016 (Smrz, et al. 2021). More concerning than the growing incidence of endometrial cancer, is its rising mortality rate that has been estimated to increase by about 2% per year despite advances in treatments (Henley, et al. 2018; Siegel, et al. 2024).

While there are several proposed mechanisms behind this increase in incidence, especially among younger women, the leading hypotheses gravitate towards the increasing rates of obesity in our population. Over the last 40 years, the incidence of obesity and endometrial cancer have climbed in tandem (Smrz, et al. 2021). Weight gain of as little as 10 pounds has been found to be associated with an increased risk of developing endometrial cancer (Luo, et al. 2017). A state of increased cellular proliferation, chronic inflammation, and oxidative stress, as well as derangements in metabolic pathways, all associated with obesity, lower the barrier for oncogenic transformation. (Hopkins, et al. 2016; Renehan, et al. 2015). High adiposity can lead to increased peripheral aromatization of androgens and a chronic state of estrogen excess that then stimulates endometrial proliferation or hyperplasia (Hopkins, et al. 2016; Renehan, et al. 2015).

Grading of endometrial cancer is based on the proportion of solid components and the degree of differentiation of cancer cells within the uterus. Grade 1 possesses less than 5% of solid non-glandular components followed by Grade 2 demonstrating 6%-50% and Grade 3 exhibiting greater than 50% solid components (Berek, et al. 2023). The grade of endometrial cancer plays a role in overall progression and prognosis of the disease as low-grade disease (1 and 2) has been shown to be correlated with lower rates of metastasis and improved overall survival compared to higher grade 3 disease (Delaloye, et al. 2000).

The loss of the tumor suppressor gene, PTEN (phosphatase and tensin homolog) is one of the most common somatic mutations seen in endometrial cancer (Yang, et al. 2015). PTEN loss in both uterine stromal and uterine epithelial tissue has been shown to rapidly lead to development of endometrial carcinoma in mice (Liang, et al. 2018). Loss of PTEN in patients with endometrial hyperplasia has been shown to carry a significant increased risk of ultimately developing endometrial cancer, though this mutation alone is not thought to be sufficient for progression to endometrial cancer without other inciting factors (Liang, et al. 2018; Renehan, et al. 2015) . Its continued association with early stage, low-grade endometrial cancer diagnoses has led the loss of PTEN to be considered an early event in the pathogenesis of endometrial cancer (Levine, et al. 1998; Watanabe, et al. 2021). Uterine specific Pten knock-out mice have been widely used for endometrial cancer study (Daikoku, et al. 2008; Vilgelm, et al. 2006).

The association between endometrial cancer and obesity has been documented extensively with clinical data; however, research into the biomolecular pathways of this relationship needs continued exploration. Leptin is the peptide hormone product of the obese (ob) gene and has been shown to regulate appetite and metabolism (Stephens, et al. 1995). Mutations in the obese gene and leptin pathway have been associated with severe early obesity (Obradovic, et al. 2021). A well-established model of human obesity is the ob/ob mouse. This is a leptin deficient mouse that has significant obesity and hyperphagia (Coleman 1978; Suriano, et al. 2021). This study aimed to investigate the impact of obesity on the development of endometrial cancer using ob/ob and Pten mouse models.

Material & Methods

Animals and Tissue Collection

All animal experiments were approved by the University of Missouri Animal Care and Use Committee. Mice were housed and bred in a designated animal care facility at the University of Missouri with controlled humidity and temperature conditions and a 12 h light/dark cycle. Pgr^cre/+Pten^f/f (Pten^d/d) (Kim, et al. 2014) were generated by crossing Pgr^cre/+ mice (Soyal, et al. 2005) with Pten ^f/f (Lesche, et al. 2002). The leptin-deficient ob/ob (Lep^ob; Strain #: 000632) mice were purchased from the Jackson Laboratory (Bar Harbor, ME, USA). Uterine tissues including endometrial cancer were collected from mice of three genotypes (ob/ob, Pten^d/d, Pten^d/dob/ob) at four different time points (1, 1.5, 2 and 3 months of age (n ≥ 5 per genotype)). For the experiment of survival rate, mice from each genotype were also monitored until the end of their lifespan (n ≥ 5 per genotype). At each end of time point, uterine tissues were fixed with 4% (vol/vol) paraformaldehyde for hematoxylin and eosin (H&E) stain and immunohistochemistry.

Hematoxylin and eosin staining and Immunohistochemistry

Cross sections of uteri from paraffin-embedded tissue in mice were sectioned at 5 μm and mounted on silane-coated slides. Sections were deparaffinized and rehydrated in a graded alcohol series. For histological analysis, H&E were stained for gross cancer assessment by pathologist (E.J.). For immunohistochemistry, sections were deparaffinized and rehydrated in a graded alcohol series. After sections retrieved antigen and removed endogenous peroxidase, it were incubated with 10% normal goat serum in PBS (pH 7.5) and incubated with primary antibody diluted in 10% normal goat serum in PBS overnight at 4°C at the following dilutions: 1:500 for anti-phospho-Histone H3 (06-570, Millipore, Billerica, MA), 1:1,000 for anti-phospho-signal transducer and activator of transcription 3 (pSTAT3) (CS-9131, Cell Signaling, Danvers, MA), 1:1000 for alpha smooth muscle actin (α-SMA) (ab5694, Abcam, Boston, MA) 1:2000 for Phospho-Akt (Ser473) (pAKT)(CS-4060, Cell Signaling), 1:200 for B-cell leukemia / lymphoma 2 (BCL2)(SC-509, Santa Cruz Biotechnology, Dallas, TX), 1:500 for insulin receptor substrate 1 (IRS1) (ab131487, Abcam), and 1:1000 for insulin like growth factor binding protein 7 (IGFBP7). On the following day, sections were washed in PBS and incubated with a secondary antibody (Vector Laboratories, Newark, CA) for 1 hour at room temperature. Then PBS containing horseradish peroxidase (HRP) incubated for an additional 45 minutes with sections. Immunoreactivity was detected using the Vectastain Elite DAB kit (Vector Laboratories). A semiquantitative grading system (H-score) was used to compare the immunohistochemical staining intensities. In detail, H-score was calculated using the following equation: H-score = Σ Pi (i), where i is the intensity of staining with a value of 1, 2, or 3 (weak, moderate, or strong, respectively) and Pi is the percentage of stained cells for each intensity, varying from 0 to 100%. The overall data of score ranged from 0 to 300.

Statistical analysis

To assess the statistical significance of parametric data, the Student’s t-test was used for data with only two groups. For data containing more than two groups, one way ANOVA was used, followed by Tukey’s post hoc test for multiple comparisons. The statistical significance of differences in survival curves was determined by Kaplan–Meier survival analysis. All data are presented as means ± SEM. p < 0.05 was considered statistically significant. All statistical analyses were performed using the Prism10 package from GraphPad (San Diego, CA, USA).

Results

The generation of endometrial cancer mouse model with obesity.

To assess the effect of obesity on endometrial cancer, we generated the mouse model for the endometrial cancer with obesity (Pgr ^Cre/+Pten^f/fob/ob; Pten^d/dob/ob) by crossing the obesity model (ob/ob) (Suriano, et al. 2021) and endometrial cancer model (Pgr ^Cre/+Pten^f/f ;Pten^d/d) (Kim, et al. 2014) To investigate the effect of obesity on mouse body size, we examined the body size of ob/ob (Obesity), Pten^d/d (endometrial cancer), and Pten^d/dob/ob (endometrial cancer with obesity) mice at 1, 1.5, 2, and 3 months of age. An increase in body size was observed in ob/ob mice and Pten^d/dob/ob mice compared to Pten^d/d mice beginning at 1.5 months of age (Supplementary Fig. 1A). The body weight at 1 month-old-age was not significantly different among the three mice (ob/ob (19.25 ± 1.06 g), Pten^d/d (15.42 ± 1.49 g), and Pten^d/dob/ob (18.42 ± 2.4 g). However, the body weight at 1.5month of age began to increase in ob/ob mice (31.05 ± 1.94g; p < 0.001) and Pten^d/dob/ob mice (29.00 ± 0.86g; p < 0.001) compared to Pten^d/d mice (18.39 ± 0.57g). The body weight difference at 2 months of age in ob/ob (41.43 ± 1.7g) vs Pten^d/d mice (22.25 ± 0.57g) ; p < 0.001, Pten^d/d (22.25 ± 0.57g) vs Pten^d/dob/ob mice (37.99 ± 4.2g); p < 0.001) and 3 months of age (ob/ob (59.77 ± 2.5g) vs Pten^d/d mice (23.86 ± 0.61g); p < 0.001, Pten^d/d (23.86 ± 0.61g) vs Pten^d/dob/ob mice (51.85 ± 1.41g ; p < 0.001) had same pattern as 1.5 months of age (Supplementary Fig. 1B). These results suggest that differences in body weight due to mutations in the leptin gene started at 1.5 months of age.

The development and progression of endometrial cancer in Pten^d/dob/ob mice

In order to investigate the effects of obesity on endometrial cancer, we examined the development and progression of endometrial cancer in the uteri of ob/ob, Pten^d/d, and Pten^d/dob/ob mice at 1, 1.5, 2, and 3 months of age. Tumor growth to the level of the uterine serosa was noted in Pten^d/d and Pten^d/dob/ob mice at 2 and 3 months of age (Fig. 1A). The uterine weight at 1 month of age was shown to be increased in Pten^d/d group (0.01 ± 0.0009g; p < 0.0001) and Pten^d/dob/ob group (0.11 ± 0.01g; p < 0.001) compared to ob/ob group (0.1 ± 0.01g). An increase in the uterine weight was observed in Pten^d/d (0.76 ± 0.07g; p < 0.001) and Pten^d/dob/ob mice (0.84 ± 0.24g; p < 0.001) compared to ob/ob mice (0.01 ± 0.002g) at 2 months of age. We observed an increase in uterine weight in Pten^d/d (1.19 ± 0.15g; p < 0.001) and Pten^d/dob/ob mice (1.83 ± 0.25g; p < 0.001) compared to ob/ob mice (0.04 ± 0.003g) at 3 months of age as well (Fig. 1B). We next examined the lifespan of ob/ob, Pten^d/d, and Pten^d/dob/ob mice. The survival time of Pten^d/d group and Pten^d/dob/ob group was also not significantly different (Supplementary Fig. 2). Pten^d/d and Pten^d/dob/ob mice revealed metastasis at 3 months of age. Although there was no difference between Pten^d/d and Pten^d/dob/ob mice on the severity of metastasis (Supplementary Fig. 3) and the obesity remarkably promoted tumorigenesis, metastasis, and tumor grade in Pten^d/dob/ob mice compared to Pten^d/d mice.

Figure 1. Development of endometrial cancer in Pten^d/dob/ob mice.

(A) Uterus anatomy representative images of uterus displayed apparent differences among groups at 1, 1.5, 2, and 3-months aged mice for ob/ob, Pten^d/d, and Pten^d/dob/ob mice. (B) Uterus weight of Pten^d/d and Pten^d/dob/ob mice from 1 month age started to demonstrate significant difference from ob/ob mice. The results represent the mean ± SEM. *, p < 0.05, **, p < 0.01, ***, p < 0.001

The development of higher-grade endometrial cancer in Pten^d/dob/ob mice

For further analysis of the effect of obesity on endometrial cancer, we performed histological analysis in our mouse model at 1, 1.5, 2, and 3 months of age. We revealed that Pten^d/d (6/7) and Pten^d/dob/ob mice (5/5) exhibited Grade I endometrial cancer at 1 month of age. All Pten^d/dob/ob mice showed Grade II endometrial cancer (4/4) whereas Pten ^d/d mice had Grade I (1/4), Grade I and II (2/4), and Grade II (1/4) endometrial cancer. Interestingly, Pten ^d/d mice at 2 months of age had all Grade I endometrial cancer (5/5) while Pten^d/dob/ob mice had Grade I (1/7) and Grade II (6/7) endometrial cancer (p < 0.0001). Lastly, Pten^d/d mice at 3 months of age had Grade I (2/5) and Grade II (3/7) while Pten^d/dob/ob group had Grade I (3/4) and Grade II (4/7) (Fig. 2B). These results suggest that obesity is associated with higher grade endometrial cancer development when Pten is mutated.

Figure 2. Histological and pathological analysis for Pten^d/d and Pten^d/dob/ob mice.

(A) Histological representative images of grade I endometrial cancer in Pten^d/d and grade II endometrial cancer in Pten^d/dob/ob mice. (B) Tumor grade in Pten^d/d and Pten^d/dob/ob mice. The results represent the mean ± SEM. ***, p < 0.001.

Increase of myometrial invasion in Pten^d/dob/ob mice.

The myometrium is the muscular layer of the uterus. Its main function is to support the form of uterus and induce uterine contractions. Endometrial cancer invasion into the myometrium is an important factor in disease staging and prognosis (Dane and Bakir 2019). α-SMA is a protein that is specifically expressed in smooth muscle cells and is a protein primarily found in the smooth muscle cells of the myometrium (Cao, et al. 2022; Shynlova, et al. 2005). Myometrial invasion is defined as the invasion of endometrial cancer cells into myometrium. It indicates the depth of cancer invasion and impacts the prognosis of the patient with endometrial cancer (Dane and Bakir 2019; Geels, et al. 2013). The extent of this invasion is a critical factor in staging cancer and determining treatment options. To investigate myometrial invasion in the uteri of Pten^d/d and Pten^d/dob/ob mice, we performed the immunohistochemistry of α-SMA. IHC α-SMA showed a significant increase in the area of myometrial invasion in the uteri of Pten^d/dob/ob mice compared to Pten^d/d mice at 1.5 month (p < 0.05) and 2 months (p < 0.05) of age (Fig. 3). These results suggest that obesity led to an increase in myometrial invasion during endometrial tumorigenesis with Pten mutation.

Figure 3. Occurrence of myometrium invasion in Pten^d/dob/ob mice.

(A) Immunohistochemical representative image of alpha smooth muscle actin at the 1.5 months and 2 months of age from Pten^d/d and Pten^d/dob/ob mice. (B) Number of myometrium invasion site on Pten^d/d and Pten^d/dob/ob mice at 1.5 months and 2 months of age (n = 5 for each genotype). The filled-in arrowhead indicates an example of myometrium invasion. The results represent the mean ± SEM. *, p < 0.05

An increase of proliferation and pSTAT3 expression in the Pten^d/dob/ob mice

To determine whether the development of endometrial cancer in Pten^d/dob/ob mice is promoted by cell proliferation or other signals, we examined the expression of Phospho-Histone H3(pHH3), which is a proliferative marker, and Phospho-Signal transducer and activator of transcription 3 (pSTAT3), which is a transcription factor implicated in oncogenic signaling pathways in endometrial cancer (Dong, et al. 2023), at 1 month,1.5 month, and 3 months of age by immunohistochemistry. Proliferation was significantly increased in the uteri of Pten^d/dob/ob mice compared to Pten^d/d mice at 1 month (p < 0.01), 1.5 month (p < 0.001), and 3 months (p < 0.01) of age (Fig. 4A and B). Phosphorylation levels of pSTAT3 were also significantly increased in the uteri of Pten^d/dob/ob mice compared Pten^d/d group at 1 month (p < 0.05), 1.5 month (p < 0.05), and 3 months (p < 0.05) of age (Fig. 4C and D). This data suggests that obesity affects endometrial tumorigenesis via alteration in highly conserved cell proliferation and cell growth pathways

Figure 4. The expression of pHH3 and pSTAT3 in Pten^d/dob/ob mice.

Immunohistochemical representative images (A) and H-score (B) of phospho-Histone H3(pHH3) on Pten^d/d and Pten^d/dob/ob mice at 1 month, 1.5 months, and 3 months of age (n = 5 for each genotype). Immunohistochemical representative images (C) and H-score (D) of pSTAT3 on Pten^d/d and Pten^d/dob/ob mice at 1 month, 1.5 months, and 3 months of age (n = 5 for each genotype). The results represent the mean ± SEM. *, p < 0.05. ***, p < 0.001

Activation of oncogenic and obesity-related molecules in the Pten^d/dob/ob mice

Phosphorylation of AKT (pAKT) is a common feature of endometrial cancer with PTEN mutations and is associated with poor prognosis (Shi, et al. 2019; Terakawa, et al. 2003). Our IHC result revealed a significant (p < 0.05) increase of pAKT by 24.56% in the endometrial cancer of Pten^d/dob/ob mice compared to Pten^d/d mice (Fig. 5 A and B). Furthermore, the expression of BCL2 (B-cell lymphoma-2) was significantly (p < 0.001) increased by 145.54% in Pten^d/dob/ob mice compared to Pten^d/d mice (Fig. 5 C and D). BCL2 is a proto-oncogene that inhibits apoptosis, and its dysfunction leads to malignancy (Sakuragi, et al. 1998). BCL2 expression is associated with many tumors including carcinoma breast, prostate lung, and endometrium (Anderson and Slotkin 1975; Kandaswamy and Palanisamy 2023; Lyndin, et al. 2022). Our IHC results support oncogenic effect of obesity in endometrial cancer with Pten deficiency.

Figure 5. The oncogenic effect of obesity on pAKT and BCL2 expression in Pten^d/dob/ob mice.

Immunohistochemical representative images (A) and H-score (B) of pAKT on Pten^d/d and Pten^d/dob/ob mice at 2 months of age (n = 5 for each genotype). Immunohistochemical representative images (C) and H-score (D) of BCL2 on Pten^d/d and Pten^d/dob/ob mice at 2 months of age (n = 5 for each genotype). The results represent the mean ± SEM. *, p < 0.05. **, p < 0.01

Furthermore, higher BMI was linked to upregulation of obesity-related genes, including insulin receptor substrate 1 (IRS1) and insulin like growth factor binding protein 7 (IGFBP7), suggesting a strong molecular basis for the role of obesity in the pathogenesis of endometrial cancer (Roque, et al. 2016). Therefore, we examined the expression of IRS1 and IGFBP7 in endometrial cancer of Pten^d/d and Pten^d/dob/ob mice. Our IHC results revealed that the expression of IRS1 was significantly (p < 0.05) increased by 18.24% in Pten^d/dob/ob mice compared to Pten^d/d mice (Fig. 6 A and B). IRS1 is an adaptor protein and is associated with cancer development, progression, and clinical outcome of patients with solid tumors, and it serves as a connecting link between insulin/InsR and its downstream pathways (Wang, et al. 2012). We also observed that IGFBP7 proteins were significantly (p < 0.05) increased by 71.96% in Pten^d/dob/ob mice compared to Pten^d/d mice (Fig. 6 C and D). IGFBP7 is a secreted protein of a family of low-affinity IGFBPs that are pro-tumorigenic and regulate tumor invasion and metastasis in the cancer (Jin, et al. 2020).

Figure 6. The expression of IRS1 and IGFBP7 in Pten^d/dob/ob mice.

Immunohistochemical representative images (A) and H-score (B) of IRS1 on Pten^d/d and Pten^d/dob/ob mice at 2 months of age (n = 5 for each genotype). Immunohistochemical representative images (C) and H-score (D) of IGFBP7 on Pten^d/d and Pten^d/dob/ob mice at 3 months of age (n = 5 for each genotype). The results represent the mean ± SEM. *, p < 0.05.

Discussion

This study reveals that ob/ob mice develop more aggressive endometrial cancer associated with Pten deficiency. Being overweight or obese is a major risk factor for several types of cancer, including uterus, breast, bowel, pancreatic, esophageal, gallbladder, ovarian, kidney, liver, upper stomach, myeloma, and meningioma (Arnold, et al. 2015; Sung, et al. 2019). Endometrial cancer is the cancer linked most strongly to obesity. The incidence of endometrial cancer has climbed as more women have become obese in the United States (Polednak 2003). As weight increases, so does the risk for endometrial cancer (Kwon and Lu 2008; Reeves, et al. 2007). Moreover, large-scale weight loss reduces endometrial cancer risk (Luo, et al. 2019; MacKintosh and Crosbie 2018; Zhang, et al. 2019). However, less is known about whether obesity influences the risk of progression of endometrial cancer in human patients. This study reveals that ob/ob mice develop more aggressive endometrial cancer associated with Pten deficiency.

Our result showed that the expression of phospho-STAT3 in leptin deficient obese mice with endometrial cancer was significantly higher than in control non-obese mice with endometrial cancer in early-stage disease. STAT3 is an oncogenic transcription factor and a member of the STAT family that plays a significant role in biological functions. STAT3 is subject to rigorous regulation by upstream signaling molecules, including Janus kinase (JAK) and epidermal growth factor receptor (EGFR) (Dong, et al. 2023; Song, et al. 2020). In the study of STAT3 function in cancer, patients with various types of malignancies who have high levels of phospho-STAT3 expression are more likely to have a bad prognosis. Activation of STAT3 in the tumor microenvironment could be considered a key event in endometrial cancer oncogenesis (Tolomeo and Cascio 2021). The leptin signaling pathway is associated with the expression of STAT3 (Buettner, et al. 2006; Zhou, et al. 2012). Leptin is involved in endocrine metabolism, appetite control, and energy expenditure. Deficiencies and reduced sensitivity to leptin lead to metabolic disorders and cancer development through dysregulation of several signaling pathways (Ghadge and Khaire 2019; Ghasemi, et al. 2019; Socol, et al. 2022). Furthermore, we demonstrated that ob/ob mice show increased activation of oncogenic and obesity-related molecules as noted by increased expression of pAKT and BCL2. Therefore, the Pten^d/dob/ob mice used in this experiment are a good model for observing the development of endometrial cancer where obesity is induced due to leptin deficiency.

In addition, we demonstrated that phosphohistone H3 was significantly increased in endometrial cancer cells from obese mice compared to the non-obese mice. Together, these data demonstrate that activation of STAT3 signaling in leptin-deficient mice with endometrial cancer contribute to the proliferation and severity of early-stage endometrial cancer. Pten^d/dob/ob mice develop higher tumor grades than Pten^d/d mice. While obese mice develop higher tumor grades in endometrial cancer than non-obese mice, this relationship has not been extensively demonstrated in humans, as obesity is most often associated with lower tumor grades and earlier stage at the time of diagnosis in humans (Everett, et al. 2003). Therefore, further studies with larger sample size are needed to determine the relationship between obesity and tumor grade in endometrial cancer.

The models also demonstrated a statistically significant difference in the level of myometrial invasion with the obese endometrial cancer model showing a greater degree of invasion compared to the non-obese endometrial cancer model at 1.5 and 2 months of age. This difference in invasion may be secondary to the acceleration of cancer development in the obese state that can also be seen in humans with many obese patients being diagnosed with endometrial cancer at an earlier age than nonobese patients (Nevadunsky, et al. 2014). A linear relationship between the severity of obesity and age at diagnosis has also been observed hinting to the underlying oncogenic mechanisms of obesity in endometrial cancer (Nevadunsky, et al. 2014). Body mass index (BMI) is associated with endometrial cancer grade and stage and is a prognostic factor for survival. One study found that patients with a BMI greater than 40 kg/m² were more likely to have lower-stage disease and lower grade tumors (Arem and Irwin 2013; Everett, et al. 2003). While obesity is more prevalent in women with lower grade tumors, some obese patients also develop aggressive tumors as well. Therefore, further pathophysiological studies are needed to explore the relationship between obesity and endometrial cancer.

Our current study also demonstrates that our model of endometrial cancer in the setting of obesity had no significant difference in survival when compared to the model for endometrial cancer in non-obese mice. Studies have shown that while obese BMI’s (>30kg/m²) in humans at the time of cancer diagnosis can be associated with an increase all-cause mortality, there has not been significant evidence demonstrating increased disease-specific mortality among endometrial cancer survivors (Kokts-Porietis, et al. 2021). There has been growing evidence to support that the common comorbidities of obesity, such as cardiovascular disease, are a leading cause of death in endometrial cancer patients, especially those with lower risk disease (Felix, et al. 2017; Ward, et al. 2012). Despite this knowledge, the cellular and molecular effects of obesity in endometrial cancer remain to be clarified. Therefore, identifying the mechanisms involved in the early tumorigenesis of obesity-related endometrial cancers is essential.

Endometrial cancer is the cancer linked most strongly to obesity. Our results demonstrate that tumorigenesis of endometrial cancer is accelerated in the obese mice compared to control mice. Our findings highlight a crucial effect for obesity in the tumorigenesis of endometrial cancer by stimulating cell proliferation and STAT3 phosphorylation. Therefore, our studies provide a potential new drug target for the intervention of human endometrial cancer in obese women.