Recurrent Endometrial Cancer: Which Is the Best Treatment? Systematic Review of the Literature

Simple Summary

Endometrial cancer is the most common gynaecological tumour in developed countries. The aim of this systematic review is to compare different therapeutic strategies in the treatment of endometrial cancer recurrence to evaluate their prognostic and curative effects. The treatment of choice should be assessed according to the relapse location and to the presence of single or multiple lesions. A crucial role is also played by the type of adjuvant treatment received at the time of the first diagnosis. The molecular pattern will also be investigated in future studies. This will make it possible to personalise treatments.

Abstract

Background: Endometrial cancer is the most common gynaecological tumour in developed countries. The overall rate of relapse has remained unchanged in recent decades. Recurrences occur in approximately 20% of endometrioid and 50% of non-endometrioid cases. The aim of this systematic review is to compare different therapeutic strategies in the treatment of endometrial cancer recurrence to evaluate their prognostic and curative effects based on site and type of recurrence. Methods: This systematic review of literature was conducted in accordance with the PRISMA guidelines. The study protocol was registered on PROSPERO (CRD42020154042). PubMed, Embase, Chocrane and Cinahl databases were searched from January 1995 to September 2021. Five retrospective studies were selected. Results: A total of 3571 studies were included in the initial search. Applying the screening criteria, 299 articles were considered eligible for full-text reading, of which, after applying the exclusion criteria, 4 studies were selected for the final analysis and included in the systematic review. No studies were included for a quantitative analysis. We divided the results according to the location of the recurrence: locoregional recurrence, abdominal recurrence and extra abdominal recurrence. Conclusion: the treatment of choice should be assessed according to the relapse location and to the presence of single or multiple lesions. A crucial role in the decision-making algorithm is also the type of adjuvant treatment received at the time of the first diagnosis.

Myelin and Lymphocyte Protein (MAL): A Novel Biomarker for Uterine Corpus Endometrial Carcinoma

Purpose

Myelin and lymphocyte protein (MAL) plays an essential role in esophageal cancer, classic Hodgkin's lymphoma and breast cancer. However, its role in uterine corpus endometrial carcinoma (UCEC) has not been explored. Therefore, the current study sought to explore the role of MAL in UCEC.

Patients and Methods

Differentially expressed genes (DEGs) were identified by using Limma package in R based on TCGA-UCEC data. Kaplan-Meier plotter analysis was performed to explore the prognostic value of MAL. Function enrichment analyses were performed using GSVA. Further, roles of MAL in UCEC were validated using clinical cohort, which included 120 tumor and adjacent tissues. qRT-PCR and immunohistochemistry analyze the samples. Chi-square tests were performed to explore the associations between MAL expressions and clinicopathological features.

Results

The findings showed that overexpression level of MAL in tumor was correlated with worse survival (p = 0.000424). MAL exhibited predictive power for survival time of UCEC patients (3 years: AUC = 0.635; 5 years: AUC = 0.635). Notably, high expression level of MAL was correlated with advanced stage of UCEC. MAL overexpression was significant in UCEC with microsatellite instability (MSI). Enrichment analysis showed that MAL was enriched mainly in MYC targets, epithelial mesenchymal transition and KRAS signaling. Furthermore, MAL was associated with infiltration of immune cells in the tumor micro-environment and immune checkpoint. Analysis showed a positive association between MAL and T cell (CD4+ memory resting). Correlation analysis showed that MAL was significantly positively correlated with several immune checkpoint, including CD274 (R = 0.3389, p = 0.0081), LAG3 (R = 0.2913, p = 0.0229), PDCD1LG2 (R = 0.5345, p < 0.0001). The prognosis value of MAL was confirmed through the experiment.

Conclusion

The findings of the current study indicated that MAL is an effective prognostic biomarker and potential therapeutic target for UCEC patients. These results indicated that MAL functions as a diagnosis and therapeutic marker in UCEC treatment.

Targeted therapies in gynecological cancers: a comprehensive review of clinical evidence

Advanced and recurrent gynecological cancers are associated with poor prognosis and lack of effective treatment. The developments of the molecular mechanisms on cancer progression provide insight into novel targeted therapies, which are emerging as groundbreaking and promising cancer treatment strategies. In gynecologic malignancies, potential therapeutic targeted agents include antiangiogenic agents, poly (ADP-ribose) polymerase (PARP) inhibitors, tumor-intrinsic signaling pathway inhibitors, selective estrogen receptor downregulators, and immune checkpoint inhibitors. In this article, we provide a comprehensive review of the clinical evidence of targeted agents in gynecological cancers and discuss the future implication.

Oncogenic PIK3CA gene mutations and HER2/neu gene amplifications determine the sensitivity of uterine serous carcinoma cell lines to GDC-0980, a selective inhibitor of Class I PI3 kinase and mTOR kinase (TORC1/2)

OBJECTIVE

To evaluate PIK3CA mutational status and c-erbB2 gene amplification in a series of primary uterine serous carcinomas (USC) cell lines. To assess the efficacy of GDC-0980, a potent inhibitor of Class I PI3 kinase and mTOR kinase (TORC1/2), against primary USC harboring HER2/neu gene amplification and/or PIK3CA mutations.

STUDY DESIGN

Twenty-two primary USC cell lines were evaluated for c-erbB2 oncogene amplification by fluorescence in situ hybridization (FISH) assays and for PIK3CA gene mutations by direct DNA sequencing of exons 9 and 20. In vitro sensitivity to GDC-0980 was evaluated by flow-cytometry-based viability and proliferation assays. Downstream cellular responses to GDC-0980 were assessed by measuring phosphorylation of the 4-EBP1 protein by flow-cytometry.

RESULTS

Five of 22 (22.7%) USC cell lines contained oncogenic PIK3CA mutations although 9 (40.9%) harbored c-erbB2 gene amplification by FISH. GDC-0980 caused a strong differential growth inhibition in FISH+ USC when compared with FISH- (GDC-0980 IC50 mean ± SEM = 0.29 ± 0.05 μM in FISH+ vs 1.09 ± 0.20 μM in FISH- tumors, P = .02). FISH+ USC harboring PIK3CA mutations were significantly more sensitive to GDC-0980 exposure when compared with USC cell lines harboring wild-type PIK3CA (P = .03). GDC-0980 growth-inhibition was associated with a significant and dose-dependent decline in phosphorylated 4-EBP1 levels.

CONCLUSION

Oncogenic PIK3CA mutations and c-erbB2 gene amplification may represent biomarkers to identify patients harboring USC who may benefit most from the use of GDC-0980.

Current status of molecular-targeted drugs for endometrial cancer (Review)

Endometrial cancer is a common gynecological malignant tumor in Western countries and its incidence has also been on the increase in Asia. Genetic abnormalities related to onset and progression of malignancy in the endometrial membrane and signaling system have been identified and the developmental mechanism of endometrial cancer is becoming elucidated. The identification of the molecules related to these abnormalities has led to new potential treatment regimens for endometrial cancer, using molecular-targeted drugs. The current chemotherapy for endometrial cancer often causes systemic side effects that require discontinuation of the treatment. Furthermore, a treatment regimen for cancers of rare histological types has not been established. Recent studies on endometrial cancer revealed patterns of genetic disorders that differ among the histological types. Genetic and molecular information that underlie pathological changes and is associated with DNA mismatch repair genes and epigenetic regulation was also identified. Targeting of these mechanisms with molecular-targeted drugs has been performed with the aim of linking treatment to the carcinogenic mechanism at the molecular and genetic levels. However, the response rates with single-agent therapy are generally low and several problems remain unresolved. Trials of combinations of molecular-targeted drugs with currently available treatments and identification of factors determining sensitivity are required to overcome these difficulties.

New candidate therapeutic agents for endometrial cancer: potential for clinical practice (review)

Cases of endometrial cancer have increased in recent years, but the prognosis of patients with this disease has also been improved by combined modality therapy with surgery, radiotherapy and chemotherapy. However, the development of new therapy is required from the perspectives of conservation of fertility and efficacy for recurrent and intractable cancer. New candidate therapeutic agents for endometrial cancer include fourth-generation progestins for inhibition of growth and differentiation of endometrial glands; metformin for reduction of hTERT expression in the endometrium and inhibition of the mTOR pathway by activation of AMPK, with consequent inhibition of the cell cycle; mTOR inhibitors for supressing growth of cancer cells by G1 cell cycle arrest; microRNAs involved in the molecular mechanisms of oncogenesis and progression; and HDAC inhibitors that block the growth of cancer cells by transcriptional elevation of tumor-suppressor genes, cell cycle arrest and induction of apoptosis. In this study, we review the background and early clinical evidence for these agents as new therapeutic candidates for endometrial cancer.

Contemporary management of endometrial cancer

The treatment of endometrial cancer has changed substantially in the past decade with the introduction of a new staging system and surgical approaches accompanied by novel adjuvant therapies. Primary surgical treatment is the mainstay of therapy but the effectiveness and extent of lymphadenectomy has been challenged, and its acceptance as a routine procedure varies by country. The role of radiation has evolved and chemotherapy has been incorporated, either alone or combined with radiation, to treat the many patients in whom cancer recurs because of a tumour outside the originally radiated pelvic and lower abdominal area. Use of traditional adjuvant chemotherapeutics has been challenged in clinical trials of new agents with improved side-effect profiles. Novel agents and targeted therapies are being investigated. Research into genetic susceptibility to endometrial cancer and the potential genetic aberrations that might translate into therapeutic interventions continues to increase. Substantial global variability in the treatment of endometrial cancer has led to examination of long-accepted norms, which has resulted in rapidly changing standards. International cooperation in clinical trials will hasten progress in treatment of this ubiquitous cancer.

Targeting the mTOR/4E-BP pathway in endometrial cancer

Endometrial cancer is the most common gynecologic malignancy. Although it is highly treatable in the early stages of disease, therapies for advanced and recurrent disease are rarely curative. A molecular and genetic understanding of endometrial cancer involves the mTOR signaling pathway, an emerging target for treatment of type I disease (the most common presentation). Endometrial cancers show a significant reliance on the mTOR pathway for survival, and studies to date have revealed a clinical advantage in targeting this pathway. Less well developed in the study of endometrial cancer is an understanding of mTOR signaling to its major downstream effector, translational control. Given the poor rate of success for treatment of late-stage endometrial cancer, increasing attention is being directed to the development of new therapeutic approaches, including targeting the mTOR pathway. Here, we discuss the potential benefit of targeting mTOR combined with existing chemotherapies by monitoring its impact on translational regulatory pathways and key translation targets in endometrial cancer. We also highlight laboratory and clinical research findings that will provide new avenues for future research and clinical development.

Antitumor activity of ridaforolimus and potential cell-cycle determinants of sensitivity in sarcoma and endometrial cancer models

Ridaforolimus is a nonprodrug rapamycin analogue that potently inhibits mTOR and has shown significant activity in patients with metastatic sarcoma and endometrial cancer, two diseases where high unmet need remains. Here, we evaluated the activity of ridaforolimus in preclinical models of these tumor types and used these models to explore molecular correlates of sensitivity. The in vitro sensitivity of a panel of sarcoma and endometrial cancer cell lines was established by measuring the effect of ridaforolimus on cell proliferation rate, revealing broad inhibition at low nanomolar concentrations. Additional benefit was found when ridaforolimus was combined with agents used to treat sarcoma and endometrial cancer patients. In vivo, potent antitumor activity of ridaforolimus associated with inhibition of mTOR signaling was observed in sarcoma and endometrial xenograft models. Immunoblot analysis was conducted to assess the expression and activation state of multiple signaling proteins in the phosphoinositide-3-kinase/AKT/mTOR and cell-cycle pathways. In endometrial but not sarcoma cell lines, the absence of PTEN or elevated levels of phosphorylated or total AKT was associated with greater sensitivity. However, in both tumor types, the proportion of cells in the G(0)-G(1) phase before treatment correlated significantly with ridaforolimus sensitivity. Consistent with this, expression of several G(1) phase cell-cycle proteins, notably p21 and p27, was higher in more sensitive lines. These results underscore the promise of ridaforolimus as a single agent or combination treatment of these tumor types and suggest novel potential predictive biomarkers of sensitivity to an mTOR inhibitor based on cell-cycle status.

Overexpression of the mammalian target of rapamycin (mTOR) and angioinvasion are poor prognostic factors in early stage NSCLC: a verification study

BACKGROUND

A recent study by Dhillon et al. [12], identified both angioinvasion and mTOR as prognostic biomarkers for poor survival in early stage NSCLC. The aim of this study was to verify the above study by examining the angioinvasion and mTOR expression profile in a cohort of early stage NSCLC patients and correlate the results to patient clinico-pathological data and survival.

METHODS

Angioinvasion was routinely recorded by the pathologist at the initial assessment of the tumor following resection. mTOR was evaluated in 141 early stage (IA-IIB) NSCLC patients (67 - squamous; 60 - adenocarcinoma; 14 - others) using immunohistochemistry (IHC) analysis with an immunohistochemical score (IHS) calculated (% positive cells×staining intensity). Intensity was scored as follows: 0 (negative); 1+ (weak); 2+ (moderate); 3+ (strong). The range of scores was 0-300. Based on the previous study a cut-off score of 30 was used to define positive versus negative patients. The impact of angioinvasion and mTOR expression on prognosis was then evaluated.

RESULTS

101 of the 141 tumors studied expressed mTOR. There was no difference in mTOR expression between squamous cell carcinoma and adenocarcinoma. Angioinvasion (p=0.024) and mTOR staining (p=0.048) were significant univariate predictors of poor survival. Both remained significant after multivariate analysis (p=0.037 and p=0.020, respectively).

CONCLUSIONS

Our findings verify angioinvasion and mTOR expression as new biomarkers for poor outcome in patients with early stage NSCLC. mTOR expressing patients may benefit from novel therapies targeting the mTOR survival pathway.

Clinical activity of mammalian target of rapamycin inhibitors in solid tumors

The phosphatidylinositol 3-kinase (PI3K)-Akt-mammalian target of rapamycin (mTOR) pathway is vital for cell metabolism, growth, and proliferation. mTOR is frequently upregulated in many tumor types and hence has become an important target in cancer treatment. Sirolimus and its derivatives (rapalogs) interact with the intracellular receptor FK506 binding protein 12 (FKBP12), forming a complex with high affinity for mTOR and thus disrupting its activity. Rapalogs are being evaluated extensively in cancer patients with different formulations and schedules. Significant clinical activity has led to their approval for the treatment of kidney cancer, mantle cell lymphoma, and subependymal giant cell astrocytoma; however, despite increasing knowledge about cancer cell biology, their activity in other malignancies is unclear. Further research is needed to identify optimal dosage, administration and targeted combination as well as the subset of patients likely to respond to mTOR/PI3K inhibition. This review focuses on a discussion of the pathway, its implications in cancer biology and results of clinical trials of rapalogs alone or in combination, organizing them by common malignancy type.

A unique spectrum of somatic PIK3CA (p110alpha) mutations within primary endometrial carcinomas

PURPOSE

The goal of this study was to comprehensively define the incidence of mutations in all exons of PIK3CA in both endometrioid endometrial cancer (EEC) and nonendometrioid endometrial cancer (NEEC).

EXPERIMENTAL DESIGN

We resequenced all coding exons of PIK3CA and PTEN, and exons 1 and 2 of KRAS, from 108 primary endometrial tumors. Somatic mutations were confirmed by sequencing matched normal DNAs. The biochemical properties of a subset of novel PIK3CA mutations were determined by exogenously expressing wild type and mutant constructs in U2OS cells and measuring levels of AKT(Ser473) phosphorylation.

RESULTS

Somatic PIK3CA mutations were detected in 52.4% of 42 EECs and 33.3% of 66 NEECs. Half (29 of 58) of all nonsynonymous PIK3CA mutations were in exons 1-7 and half were in exons 9 and 20. The exons 1-7 mutations localized to the ABD, ABD-RBD linker and C2 domains of p110α. Within these regions, Arg88, Arg93, Gly106, Lys111, Glu365, and Glu453, were recurrently mutated; Arg88, Arg93, and Lys111 formed mutation hotspots. The p110α-R93W, -G106R, -G106V, -K111E, -delP449-L455, and -E453K mutants led to increased levels of phospho-AKT(Ser473) compared to wild-type p110α. Overall, 62% of exons 1-7 PIK3CA mutants and 64% of exons 9-20 PIK3CA mutants were activating; 72% of exon 1-7 mutations have not previously been reported in endometrial cancer.

CONCLUSIONS

Our study identified a new subgroup of endometrial cancer patients with activating mutations in the amino-terminal domains of p110α; these patients might be appropriate for consideration in clinical trials of targeted therapies directed against the PI3K pathway.

A phase I study of temsirolimus and metformin in advanced solid tumours

The purpose of this phase I trial was to establish the maximum tolerated dose and define the dose-limiting toxicities of a combination of temsirolimus and metformin. Patients with advanced solid tumours who had exhausted standard treatment options were eligible. Treatment included weekly intravenous temsirolimus and daily oral metformin. Eleven patients were enrolled. Dose-limiting toxicities were observed in all patients at the initial dose level of 25 mg weekly of temsirolimus and metformin 500 mg po BID. At dose level -1, 2 of 8 patients experienced dose-limiting toxicities. Toxicities included grade 4 pneumonitis, persistent grade 3 fatigue, and thrombocytopenia requiring dose delays. The maximum tolerated dose (level -1) was 20 mg temsirolimus weekly and 500 mg po daily of metformin. One patient with head and neck cancer experienced a partial response. Five patients had stable disease including a patient with melanoma who had stable disease for 22 months.

Emerging drugs in endometrial cancers

IMPORTANCE OF THE FIELD

Endometrial cancer remains the most common gynecologic malignancy. The treatment of endometrial cancer is rapidly evolving.

AREAS COVERED IN THIS REVIEW

In this article, we aim to review current and future treatment options in the medical treatment of endometrial cancers.

WHAT THE READER WILL GAIN

The cornerstone of curative therapy for patients with endometrial cancer is surgical treatment. Cytotoxic chemotherapy is the mainstay of therapy for metastatic and advanced endometrial cancer. The most active chemotherapy agents are anthracyclines, platinum compounds and taxanes. Combination chemotherapy has produced higher response rates than single agent therapy. Cisplatin and doxorubicin combination chemotherapy has served as the control arm in many trials. Three-drug combination regimen has shown the highest response rate but with increased toxicity. Despite the lack of published data supporting the superiority of the paclitaxel plus carboplatin combination over doxorubicin and cisplatin, many centers prefer this regimen as a standard of care. Hormonal therapy should be considered in patients with low grade tumors and in those with a poor performance status. Recent advances in the understanding of the molecular biology of endometrial cancer have led to development of targeted therapies. Among these the more promising ones are mTOR inhibitors and antiangiogenic agents.

TAKE HOME MESSAGE

Clinical trials are planned to further explore how to best incorporate novel agents into the current treatment algorithm with the aim to improve outcome for women with endometrial adenocarcinomas.

A phase 2 study of the oral mammalian target of rapamycin inhibitor, everolimus, in patients with recurrent endometrial carcinoma

BACKGROUND

Dysregulation of phosphatase and tensin homolog (PTEN) and the gene that encodes the p110α catalytic subunit of phosphatidylinositol-3-kinase (PI3K), PIK3CA, are the most common mutations in endometrial carcinoma (EC). Loss of PTEN or activation of PIK3CA results in constitutive activation of AKT, which leads to up-regulation of mammalian target of rapamycin (mTOR). Everolimus is an oral rapamycin analog that acts by selectively inhibiting mTOR.

METHODS

A single-institution, open-labeled, phase 2 study of everolimus in patients with measurable recurrent EC who had failed at least 1 and no more than 2 prior chemotherapeutic regimens was performed. Everolimus was administered at a dose of 10 mg orally daily for 28-day cycles. Patients were treated until disease progression or toxicity. The primary endpoint was clinical benefit response (CBR), defined as a confirmed complete or partial response or prolonged stable disease (SD) (≥8 weeks). Inclusion was limited to patients with endometrioid histology.

RESULTS

A total of 35 patients were enrolled (median age, 58 years; range, 38-81 years). A total of 81 cycles were administered. Twelve of 28 (43%) evaluable patients had not developed disease progression at the time of the first objective evaluation (8 weeks). All these patients had SD (median, 4.5 cycles; range, 2-10 cycles). Six of the 28 (21%) patients had a confirmed CBR at 20 weeks of therapy. Patients with CBR discontinued treatment because of toxicity (6 patients), disease progression (5 patients), and noncompliance (1 patient). Seven patients were unevaluable after receiving ≤1 cycle because of toxicity (5 patients) or noncompliance (2 patients). The most common drug-related toxicities were fatigue, anemia, pain, lymphopenia, and nausea.

CONCLUSIONS

Everolimus demonstrated encouraging single-agent CBR in pretreated patients with recurrent endometrioid EC. Future studies will evaluate this agent in combination with hormonal and/or cytotoxic therapy.

Treatment for advanced and recurrent endometrial carcinoma: combined modalities

Women with recurrent or advanced endometrial cancer constitute a heterogeneous group of patients. Depending on previous treatment, women with recurrent endometrial cancer may be appropriate candidates for surgery, radiation therapy, hormonal therapy, or chemotherapy. Women with advanced stage disease at presentation may also be appropriate candidates for systemic and local therapies. We review the treatment options available to treat recurrent and locally advanced endometrial cancer. Treatment choice depends largely on the localization of disease, the patient's performance status and previous treatment history, as well the tumor's hormonal receptor status. Radiation therapy is appropriate for isolated vaginal recurrences in patients with no previous history of radiation therapy. Patients with recurrent low-grade tumors overexpressing estrogen and progesterone receptors may be treated with progestin therapy. Systemic therapy is appropriate for patients with disseminate recurrences or advanced stage disease at presentation, or for those with receptor-negative tumors. We review all these different treatment strategies available to patients with advanced or recurrent endometrial cancer.

Prognostic value of microsatellite instability (MSI) and PTEN expression in women with endometrial cancer: results from studies of the NCIC Clinical Trials Group (NCIC CTG)

AIM

The impact of PTEN status and microsatellite instability (MSI) on the prognosis of women with endometrial cancer is controversial. The aim of this study was to investigate MSI and PTEN expression in two patient populations using data from NCIC CTG studies.

METHODS

Archival paraffin embedded tumour from women with endometrial cancer enrolled in NCIC CTG studies: EN5 (stage I/II) and IND 126, 148 and 160 (advanced/recurrent disease) were examined for MSI using BAT25/26 and for PTEN expression using immunohistochemistry. PTEN and MSI status were correlated with clinicopathologic variables and survival using data from NCIC CTG trial databases.

RESULTS

PTEN and MSI results were available from 128 and 163 patients, respectively. MSI+ tumours were more common in women enrolled in EN5 compared to the IND studies (p=0.01). PTEN negative tumours were associated with improved survival in both univariate (hazard ratio (HR) 0.55, 95% confidence interval (CI) 0.32-0.94; p=0.03) and multivariate (adjusted HR 0.54, 95% CI 0.30-0.96; p=0.03) analyses in women enrolled in IND studies. Microsatellite stable tumours were associated with an improved prognosis in univariate (HR 0.18, 95% CI 0.06-0.51; p<0.0001) and multivariate (adjusted HR 0.16, 95% CI 0.05-0.5; p<0.0001) analyses in women enrolled in EN5. There was no significant correlation between MSI and PTEN status.

CONCLUSIONS

PTEN negative tumours in women with advanced disease are associated with improved survival. MSI+ tumours are more common in early stage disease and in this group of women are associated with a worse prognosis.

mTOR signaling and drug development in cancer

Mammalian target of rapamycin (mTOR) is a protein kinase of the PI3K/Akt signaling pathway. Activation of mTOR in response to growth, nutrient and energy signals leads to an increase in protein synthesis, which is required for tumor development. This feature makes mTOR an attractive target for cancer therapy. First-generation mTOR inhibitors are sirolimus derivatives (rapalogs), which have been evaluated extensively in cancer patients. Everolimus and temsirolimus are already approved for the treatment of renal-cell carcinoma. Temsirolimus is also approved for the treatment of mantle-cell lymphoma. These drugs, in addition to ridaforolimus (formerly deforolimus) and sirolimus, are currently being evaluated in clinical trials of various cancers. Second-generation mTOR inhibitors are small molecules that target the kinase domain, and have also entered clinical development. Clinical trials are underway to identify additional malignancies that respond to mTOR inhibitors, either alone or in combination with other therapies. Future research should evaluate the optimal drug regimens, schedules, patient populations, and combination strategies for this novel class of agents.

Lkb1 inactivation is sufficient to drive endometrial cancers that are aggressive yet highly responsive to mTOR inhibitor monotherapy

Endometrial cancer--the most common malignancy of the female reproductive tract--arises from the specialized epithelial cells that line the inner surface of the uterus. Although significant advances have been made in our understanding of this disease in recent years, one significant limitation has been the lack of a diverse genetic toolkit for the generation of mouse models. We identified a novel endometrial-specific gene, Sprr2f, and developed a Sprr2f-Cre transgene for conditional gene targeting within endometrial epithelium. We then used this tool to generate a completely penetrant Lkb1 (also known as Stk11)-based mouse model of invasive endometrial cancer. Strikingly, female mice with homozygous endometrial Lkb1 inactivation did not harbor discrete endometrial neoplasms, but instead underwent diffuse malignant transformation of their entire endometrium with rapid extrauterine spread and death, suggesting that Lkb1 inactivation was sufficient to promote the development of invasive endometrial cancer. Mice with heterozygous endometrial Lkb1 inactivation only rarely developed tumors, which were focal and arose with much longer latency, arguing against the idea--suggested by some prior studies--that Lkb1 is a haploinsufficient tumor suppressor. Lastly, the finding that endometrial cancer cell lines were especially sensitive to the mTOR (mammalian target of rapamycin) inhibitor rapamycin prompted us to test its efficacy against Lkb1-driven endometrial cancers. Rapamycin monotherapy not only greatly slowed disease progression, but also led to striking regression of pre-existing tumors. These studies demonstrate that Lkb1 is a uniquely potent endometrial tumor suppressor, but also suggest that the clinical responses of some types of invasive cancers to mTOR inhibitors may be linked to Lkb1 status.

Promising novel therapies for the treatment of endometrial cancer

OBJECTIVES

To discuss the novel agents which are being developed for the treatment of advanced and recurrent endometrial carcinoma and to review other molecular targets that may be interesting in the treatment of this disease. While the majority of women with endometrial cancer enjoy a relatively good prognosis, the options for those women who suffer from a disease recurrence are limited and there is a need to identify novel agents.

METHODS

A review of clinical trials of novel therapeutic agents and their molecular targets is provided. In addition, a review of the current literature on other potential molecular targets for endometrial cancer was performed.

RESULTS

Several phase II trials of novel agents, both alone and in combination with traditional cytotoxic chemotherapy, have been completed or are nearing completion. It appears that the targeted agents may have the most efficacy in combination with cytotoxic chemotherapy or in a multi-targeted agent approach.

CONCLUSIONS

Chemotherapy offers the opportunity for a meaningful response rate in women with endometrial cancer, but the responses are often short lived and cure is uncommon in the setting of recurrent disease. The recent increase in molecular targets has led to the availability of many novel therapies. Determining how these agents are to be used, alone or in combination with "standard" therapies, needs to be defined and translational studies are needed to develop rational combinations of these novel agents before we can move into clinical trials.

The role of mTOR in the management of solid tumors: an overview

Mammalian target of rapamycin (mTOR) is a key protein kinase controlling signal transduction from various growth factors and upstream proteins to the level of mRNA and ribosome with a regulatory effect on cell cycle progression, cellular proliferation and growth. TOR genes were discovered rather serendipitously while investigating the cause of resistance to immunosuppressant rapamycin in yeast. In normal cells, mTOR controls brilliantly the load of signals from its effectors resulting in a normal cell function. On the contrary, in various diseases and mainly in cancer this balance is lost due to mutations or overactivation of upstream pathways leading to a persistent proliferation and tumor growth. What makes mTOR attractive to researchers seems to be its key position which is on the crossroad of various signal pathways (Ras, PI3K/Akt, TSC, NF-kappaB) towards mRNA, ribosome, protein synthesis and translation of significant molecules, the uncontrolled production of which may lead to tumor proliferation and growth. Inhibition of mTOR by rapamycin (a natural product) or its analogs aims to prevent the deleterious effects of the abnormal signaling, regardless at which point of the signal pathway has the abnormality launched. Here, we will review the physiological functions of mTOR, its association to carcinogenesis and the latest evidence regarding the use of mTOR inhibitors in cancer treatment as well as future trends and aims of research.

Molecular target therapies in endometrial cancer: from the basic research to the clinic

Molecular targeted therapies represent an interesting field of pharmacological research in endometrial cancer. The loss of PTEN (phosphatase and tensin homolog deleted on chromosome 10) function, with consequent activation of the PI3K (phosphatidylinositol-3-kinase)-AKT (serine/threonine-specific protein kinase)-mTOR (mammalian target of rapamycin) signaling pathway, occurs in 32-83% of endometrioid-type endometrial carcinomas, thus suggesting a role for mTOR inhibition in this malignancy. Some analogues of rapamycin (CCI-799, RAD-001, AP-23573) have been developed and tested in different tumors including endometrioid-type endometrial carcinoma. For example, AP-23573 achieved a clinical benefit response in 33% of 27 heavily pretreated patients, and CCI-799 obtained a 26% partial response rate and a 63% stable disease rate in 19 patients. Overexpression of ErbB-2 (epidermal growth factor type II receptor) has been detected in 18-80% of uterine papillary serous carcinomas (UPSCs), thus providing a biological rationale for the use of trastuzumab in these aggressive tumors. UPSC often overexpresses claudin-3 and claudin-4, which represent the epithelial receptors for Clostridium perfringens enterotoxin (CPE). CPE-mediated therapy might be a novel treatment modality for UPSC resistant to chemotherapy. A better understanding of the signaling transduction pathways that are dysregulated in endometrioid-type endometrial carcinoma and UPSC will allow the development of novel molecular targeted therapies.

Targeting the mTOR signaling network in cancer

The mammalian target of rapamycin (mTOR) is an unconventional protein kinase that is centrally involved in the control of cancer cell metabolism, growth and proliferation. The mTOR pathway has attracted broad scientific and clinical interest, particularly in light of the ongoing clinical cancer trials with mTOR inhibitors. The mixed clinical results to date reflect the complexity of both cancer as a disease target, and the mTOR signaling network, which contains two functionally distinct mTOR complexes, parallel regulatory pathways, and feedback loops that contribute to the variable cellular responses to the current inhibitors. In this review, we discuss the regulatory pathways that govern mTOR activity, and highlight clinical results obtained with the first generation of mTOR inhibitors to reach the oncology clinics.

The mammalian target of rapamycin signaling pathway: twists and turns in the road to cancer therapy

The immunosuppressive drug rapamycin played a key role in the functional characterization of mammalian target of rapamycin (mTOR), an unusual protein kinase that coordinates growth factor and nutrient availability with cell growth and proliferation. Several rapamycin-related compounds are now in various stages of clinical development as anticancer agents. This article highlights recent advances in our understanding of the mTOR signaling pathway and the implications of these findings for the clinical application of mTOR inhibitors in cancer patients.

Investigating mammalian target of rapamycin inhibitors for their anticancer properties

The mammalian target of rapamycin (mTOR) is a key element of the PI3KAkt (protein kinase B) signalling pathway, responsible for the regulation of cell growth and proliferation. There are two main downstream messengers of the mTOR kinase, eukaryotic initiation factor 4E-binding protein-1 and the 40S ribosomal protein S6 kinase 1, that control translation and cell-cycle progression. Abnormal activation of the mTOR pathway occurs frequently in numerous human malignancies; therefore, mTOR represents an attractive target for anticancer drug development. Rapamycin and its analogues CCI-779, RAD-001 and AP-23573 are known specific inhibitors of the mTOR kinase. Several clinical Phase I/II trials showed their activity in solid tumours and haematological malignancies. Moreover, inhibitors of mTOR were found to synergise with some cytostatics or other biological agents, which seems to be a promising direction for future strategies of antitumour treatment.