mTOR Signaling in Endometrial Cancer: From a Molecular and Therapeutic Point of View

Aging, oxidative stress and degenerative diseases: mechanisms, complications and emerging therapeutic strategies

Aging accompanied by several age-related complications, is a multifaceted inevitable biological progression involving various genetic, environmental, and lifestyle factors. The major factor in this process is oxidative stress, caused by an abundance of reactive oxygen species (ROS) generated in the mitochondria and endoplasmic reticulum (ER). ROS and RNS pose a threat by disrupting signaling mechanisms and causing oxidative damage to cellular components. This oxidative stress affects both the ER and mitochondria, causing proteopathies (abnormal protein aggregation), initiation of unfolded protein response, mitochondrial dysfunction, abnormal cellular senescence, ultimately leading to inflammaging (chronic inflammation associated with aging) and, in rare cases, metastasis. RONS during oxidative stress dysregulate multiple metabolic pathways like NF-κB, MAPK, Nrf-2/Keap-1/ARE and PI3K/Akt which may lead to inappropriate cell death through apoptosis and necrosis. Inflammaging contributes to the development of inflammatory and degenerative diseases such as neurodegenerative diseases, diabetes, cardiovascular disease, chronic kidney disease, and retinopathy. The body's antioxidant systems, sirtuins, autophagy, apoptosis, and biogenesis play a role in maintaining homeostasis, but they have limitations and cannot achieve an ideal state of balance. Certain interventions, such as calorie restriction, intermittent fasting, dietary habits, and regular exercise, have shown beneficial effects in counteracting the aging process. In addition, interventions like senotherapy (targeting senescent cells) and sirtuin-activating compounds (STACs) enhance autophagy and apoptosis for efficient removal of damaged oxidative products and organelles. Further, STACs enhance biogenesis for the regeneration of required organelles to maintain homeostasis. This review article explores the various aspects of oxidative damage, the associated complications, and potential strategies to mitigate these effects.

Autophagy Machinery as a Promising Therapeutic Target in Endometrial Cancer

Endometrial cancer is the fourth most frequent neoplasia for women worldwide, and over the past two decades it incidence has increased. The most common histological type of endometrial cancer is endometrioid adenocarcinoma, also known as type 1 endometrial cancer. Endometrioid endometrial cancer is associated with diverse epidemiological risk factors including estrogen use, obesity, diabetes, cigarette smoking, null parity, early menarche, and late menopause. Clinical effectiveness of chemotherapy is variable, indicating that novel molecular therapies against specific cellular processes associated to cell survival and resistance to therapy, such as autophagy, urged to ameliorate the rates of success in endometrial cancer treatment. Autophagy (also known as macroautophagy) is a specialized mechanism that maintains cell homeostasis which is activated in response to cellular stressors including nutrients deprivation, amino acids starvation, hypoxia, and metabolic stress to prolong cell survival via lysosomal degradation of cytoplasmic macromolecules and organelles. However, in human cancer cells, autophagy has a controversial function due to its dual role as self-protective or apoptotic. Conventional antitumor therapies including hormones, chemotherapy and ionizing radiation, may activate autophagy as a pro-survival tumor response contributing to treatment resistance. Intriguingly, if autophagy continues above reversibility of cell viability, autophagy can result in apoptosis of tumor cells. Here, we have reviewed the mechanisms of autophagy described in endometrial cancers, including the role of PI3K/AKT/mTOR, AMPK-mTOR, and p53 signaling pathways that trigger or inhibit the process and thus representing potential molecular targets in therapeutic clinical approaches. In addition, we discussed the recent findings indicating that autophagy can be modulated using repurposing drugs which may leads to faster experimentation and validation, as well as more easy access of the medications to patients. Finally, the promising role of dietary compounds and microRNAs in autophagy modulation is also discussed. In conclusion, although the research about autophagy is scarce but ongoing in endometrial cancer, the actual findings highlight the promising usefulness of novel molecules for directing targeted therapies.

Corilagin inhibits breast cancer growth via reactive oxygen species-dependent apoptosis and autophagy

Corilagin is a component of Phyllanthus urinaria extract and has been found of possessing anti‐inflammatory, anti‐oxidative, and anti‐tumour properties in clinic treatments. However, the underlying mechanisms in anti‐cancer particularly of its induction of cell death in human breast cancer remain undefined. Our research found that corilagin‐induced apoptotic and autophagic cell death depending on reactive oxygen species (ROS) in human breast cancer cell, and it occurred in human breast cancer cell (MCF‐7) only comparing with normal cells. The expression of procaspase‐8, procaspase‐3, PARP, Bcl‐2 and procaspase‐9 was down‐regulated while caspase‐8, cleaved PARP, caspase‐9 and Bax were up‐regulated after corilagin treatment, indicating apoptosis mediated by extrinsic and mitochondrial pathways occurred in MCF‐7 cell. Meanwhile, autophagy mediated by suppressing Akt/mTOR/p70S6K pathway was detected with an increase in autophagic vacuoles and LC3‐II conversion. More significantly, inhibition of autophagy by chloroquine diphosphate salt (CQ) remarkably enhanced apoptosis, while the caspase inhibitor z‐VAD‐fmk failed in affecting autophagy, suggesting that corilagin‐induced autophagy functioned as a survival mechanism in MCF‐7 cells. In addition, corilagin induced intracellular reactive oxygen species (ROS) generation, when reduced by ROS scavenger NAC, apoptosis and autophagy were both down‐regulated. Nevertheless, in SK‐BR3 cell which expressed RIP3, necroptosis inhibitor Nec‐1 could not alleviate cell death induced by corilagin, indicating necroptosis was not triggered. Subcutaneous tumour growth in nude mice was attenuated by corilagin, consisting with the results in vitro. These results imply that corilagin inhibits cancer cell proliferation through inducing apoptosis and autophagy which regulated by ROS release.

Insulin-Like Growth Factor 1/Mammalian Target of Rapamycin and AMP-Activated Protein Kinase Signaling Involved in the Effects of Metformin in the Human Endometrial Cancer

BACKGROUND

Metformin is a well-tolerated biguanide drug used for decades to treat type 2 diabetes mellitus. In recent years, long-term administration of metformin has been found to reduce carcinogenic risk for cancers derived from various tissues. However, its cellular and molecular mechanisms of anticancer action in the endometrial cancer (EC) have not yet been fully elucidated.

PATIENTS AND METHODS

Sixty patients diagnosed as endometrial carcinoma were grouped into (n = 30) and non-treatment mixed (n = 30) for analysis. Thirty healthy donors are control groups. We attempt to investigate the interaction of metformin, insulin-like growth factor 1 (IGF-1) expression, and phosphorylated mammalian target of rapamycin (p-mTOR) and AMP-activated protein kinase (p-AMPK).

RESULTS

We found that high IGF-1 plasma concentrations in women with EC were reversed by conventional antidiabetic doses of metformin in the present work. In parallel, the activation of AMPK and suppression of mTOR seemed to play an important role for the effect of metformin in patients with EC.

CONCLUSIONS

This pilot trial presents biological evidence consistent with antiproliferative effects of metformin in women with EC in the clinical setting.

Autophagy inhibition augments resveratrol-induced apoptosis in Ishikawa endometrial cancer cells

Resveratrol (RSV), a polyphenolic compound derived from red wine, inhibits the proliferation of various types of cancer. RSV induces apoptosis in cancer cells, while enhancing autophagy. Autophagy promotes cancer cell growth by driving cellular metabolism, which may counteract the effect of RSV. The present study aimed to elucidate the correlation between RSV and autophagy and to examine whether autophagy inhibition may enhance the antitumor effect of RSV in endometrial cancer cells. Cell proliferation, cell cycle progression and apoptosis were examined, following RSV exposure, by performing MTT assays, flow cytometry and annexin V staining, respectively, in an Ishikawa endometrial cancer cell line. Autophagy was evaluated by measuring the expression levels of light chain 3, II (LC3-II; an autophagy marker) by western blotting and immunofluorescence. Chloroquine (CQ) and small interfering RNAs targeting autophagy related (ATG) gene 5 (ATG5) or 7 (ATG7) were used to inhibit autophagy, and the effects in combination with RSV were assessed using MTT assays. RSV treatment suppressed cell proliferation in a dose-dependent manner in Ishikawa cells. In addition, RSV exposure increased the abundance of the sub-G1 population and induced apoptosis. LC3-II accumulation was observed following RSV treatment, indicating that RSV induced autophagy. Combination treatment with CQ and RSV more robustly suppressed growth inhibition and apoptosis, compared with RSV treatment alone. Knocking down ATG5 or ATG7 expression significantly augmented RSV-induced apoptosis. The results of the present study indicated that RSV-induced autophagy may counteract the antitumor effect of RSV in Ishikawa cells. Combination treatment with RSV and an autophagy inhibitor, such as CQ, may be an attractive therapeutic option for treating certain endometrial cancer cells.

A case of lymphangioleiomyomatosis associated with endometrial cancer and severe systemic lupus erythematosus

Background

Lymphangioleiomyomatosis (LAM) is a rare idiopathic disorder that occurs in women of childbearing age, and consists of a diffuse proliferation of abnormal smooth muscle cells along the thoracic and abdominal lymphogenous route.

Case presentation

We experienced a case of a 47-yo woman with recent history of systemic lupus erythematosus (SLE) diagnosed with endometrial cancer, initially suspected to have metastasized to pelvic and para-aortic lymph nodes based on preoperative diagnostic imaging. Subsequent pathological diagnosis revealed stage IB endometrial cancer without evidence of lymph node involvement. Instead, enlarged pelvic and para-aortic lymph nodes were found to be due to extrapulmonary LAM, from a primary lesion found inside the uterine myometrium. SLE improved after surgery.

Conclusion

This is the first reported case of comorbid endometrial cancer, SLE, and aggressive LAM metastasizing to regional lymph nodes, and strengthens the clinical evidence for a common role of mTOR pathway hyperactivity and estrogen responsiveness in the pathophysiology of metastasizing lesions of the genital tract.

Significance of survivin as a prognostic factor and a therapeutic target in endometrial cancer

INTRODUCTION

Survivin is an anti-apoptotic protein encoded by the baculoviral inhibitor of apoptosis repeat-containing (BIRC5) gene and is upregulated in 83% of endometrial cancers. We aimed to elucidate the prognostic importance of BIRC5 expression, and evaluate survivin as a therapeutic target for endometrial cancer, by knock-down of BIRC5 and using the survivin inhibitor-YM155.

METHODS

RNA sequencing data in 234 patients with endometrial carcinoma was obtained from The Cancer Genome Atlas database, and analyzed using Kaplan-Meier method, log-rank test and Cox proportional hazard model. Expressions of survivin in 16 endometrial cancer cell lines were analyzed by western blotting. Knocking down effect on survivin expression was evaluated using a small interfering RNA (siRNA). The anti-proliferative and pro-apoptotic effects of YM155 were assessed with cell viability, flow cytometry, and annexin V/propidium iodide assays.

RESULTS

High expression of BIRC5 was associated with poor progression free survival (P=0.006), and shown to be an independent prognostic factor (HR=1.97, 95% CI=1.29-4.5, P=0.045). Survivin was upregulated in 14 of 16 (87.5%) endometrial cancer cell lines, compared with endometrial immortalized cells. Apoptosis was induced by knockdown of BIRC5 in all 3 cell lines examined. YM155 showed increased population of sub-G1 cells (P<0.001) in all 16 cell lines, and IC50 values to YM155 were <50nm in 15 cell lines. YM155 dose-dependently and significantly increased the apoptotic cell population in all 16 cell lines (P<0.001).

CONCLUSIONS

Present study indicated that survivin expression is a significant prognostic factor and that survivin is a promising therapeutic target for endometrial cancer.