Results of an abbreviated phase II study of AKT inhibitor MK-2206 in the treatment of recurrent platinum-resistant high grade serous ovarian, fallopian tube, or primary peritoneal carcinoma (NCT 01283035)

An Update on Physiopathological Roles of Akt in the ReprodAKTive Mammalian Ovary

The phosphoinositide 3-kinase (PI3K)/Akt pathway is a key signaling cascade responsible for the regulation of cell survival, proliferation, and metabolism in the ovarian microenvironment. The optimal finetuning of this pathway is essential for physiological processes concerning oogenesis, folliculogenesis, oocyte maturation, and embryo development. The dysregulation of PI3K/Akt can impair molecular and structural mechanisms that will lead to follicle atresia, or the inability of embryos to reach later stages of development. Due to its pivotal role in the control of cell proliferation, apoptosis, and survival mechanisms, the dysregulation of this molecular pathway can trigger the onset of pathological conditions. Among these, we will focus on diseases that can harm female fertility, such as polycystic ovary syndrome and premature ovarian failure, or women's general health, such as ovarian cancer. In this review, we report the functions of the PI3K/Akt pathway in both its physiological and pathological roles, and we address the existing application of inhibitors and activators for the balancing of the molecular cascade in ovarian pathological environments.

Targeting the PI3K Pathway in Gynecologic Malignancies

PURPOSE OF REVIEW

This review explores the PI3K pathway aberrations common in gynecologic malignancies, the relevant therapeutic targets that have been explored to date particularly given their success in endometrial cancers, and predictive biomarkers of response to therapy.

RECENT FINDINGS

Landmark trials have been noted involving this pathway, particularly in endometrial cancers. One phase II trial of the potent orally bioavailable mTOR inhibitor, everolimus, in combination with letrozole demonstrated an unprecedented clinical benefit rate (CBR) of 40% and high objective response rate (RR) of 32% in hormone agnostic endometrial cancers. This was followed by GOG 3007 that compared everolimus and letrozole to hormonal therapy yielding similar response rates but double progression-free survival rates. The phosphoinositide 3-kinase (PI3K) signaling pathway is implicated in tumorigenesis given its regulation over cell growth, cellular trafficking, and angiogenesis. In gynecologic malignancies, alterations in PI3K signaling are common. Therefore, developing modulators of the PI3K pathway and identifying molecular markers to predict response are of great interest for these cancer types.

Repression of the iron exporter ferroportin may contribute to hepatocyte iron overload in individuals with type 2 diabetes

OBJECTIVE

Hyperferremia and hyperferritinemia are observed in patients and disease models of type 2 diabetes mellitus (T2DM). Likewise, patients with genetic iron overload diseases develop diabetes, suggesting a tight link between iron metabolism and diabetes. The liver controls systemic iron homeostasis and is a central organ for T2DM. Here, we investigate how the control of iron metabolism in hepatocytes is affected by T2DM.

METHODS

Perls Prussian blue staining was applied to analyze iron distribution in liver biopsies of T2DM patients. To identify molecular mechanisms underlying hepatocyte iron accumulation we established cellular models of insulin resistance by treatment with palmitate and insulin.

RESULTS

We show that a subset of T2DM patients accumulates iron in hepatocytes, a finding mirrored in a hepatocyte model of insulin resistance. Iron accumulation can be explained by the repression of the iron exporter ferroportin upon palmitate and/or insulin treatment. While during palmitate treatment the activation of the iron regulatory hormone hepcidin may contribute to reducing ferroportin protein levels in a cell-autonomous manner, insulin treatment decreases ferroportin transcription via the PI3K/AKT and Ras/Raf/MEK/ERK signaling pathways.

CONCLUSION

Repression of ferroportin at the transcriptional and post-transcriptional level may contribute to iron accumulation in hepatocytes observed in a subset of patients with T2DM.

Targeting the PI3K/AKT/mTOR pathway in epithelial ovarian cancer, therapeutic treatment options for platinum-resistant ovarian cancer

The survival rates for women with ovarian cancer have shown scant improvement in recent years, with a 5-year survival rate of less than 40% for women diagnosed with advanced ovarian cancer. High-grade serous ovarian cancer (HGSOC) is the most lethal subtype where the majority of women develop recurrent disease and chemotherapy resistance, despite over 70%-80% of patients initially responding to platinum-based chemotherapy. The phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway regulates many vital processes such as cell growth, survival and metabolism. However, this pathway is frequently dysregulated in cancers including different subtypes of ovarian cancer, through amplification or somatic mutations of phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), amplification of AKT isoforms, or deletion or inactivation of PTEN. Further evidence indicates a role for the PI3K/AKT/mTOR pathway in the development of chemotherapy resistance in ovarian cancer. Thus, targeting key nodes of the PI3K/AKT/mTOR pathway is a potential therapeutic prospect. In this review, we outline dysregulation of PI3K signaling in ovarian cancer, with a particular emphasis on HGSOC and platinum-resistant disease. We review pre-clinical evidence for inhibitors of the main components of the PI3K pathway and highlight past, current and upcoming trials in ovarian cancers for different inhibitors of the pathway. Whilst no inhibitors of the PI3K/AKT/mTOR pathway have thus far advanced to the clinic for the treatment of ovarian cancer, several promising compounds which have the potential to restore platinum sensitivity and improve clinical outcomes for patients are under evaluation and in various phases of clinical trials.

Fumarate inhibits PTEN to promote tumorigenesis and therapeutic resistance of type2 papillary renal cell carcinoma

Fumarate is an oncometabolite. However, the mechanism underlying fumarate-exerted tumorigenesis remains unclear. Here, utilizing human type2 papillary renal cell carcinoma (PRCC2) as a model, we show that fumarate accumulates in cells deficient in fumarate hydratase (FH) and inhibits PTEN to activate PI3K/AKT signaling. Mechanistically, fumarate directly reacts with PTEN at cysteine 211 (C211) to form S-(2-succino)-cysteine. Succinated C211 occludes tethering of PTEN with the cellular membrane, thereby diminishing its inhibitory effect on the PI3K/AKT pathway. Functionally, re-expressing wild-type FH or PTEN C211S phenocopies an AKT inhibitor in suppressing tumor growth and sensitizing PRCC2 to sunitinib. Analysis of clinical specimens indicates that PTEN C211 succination levels are positively correlated with AKT activation in PRCC2. Collectively, these findings elucidate a non-metabolic, oncogenic role of fumarate in PRCC2 via direct post-translational modification of PTEN and further reveal potential stratification strategies for patients with FH loss by combinatorial AKTi and sunitinib therapy.

Chemotherapy resistance in epithelial ovarian cancer: Mechanisms and emerging treatments

Ovarian cancer (OC) remains a fatal malignancy because most patients experience recurrent disease, which is resistant to chemotherapy. The outcomes for patients with platinum-resistant OC are poor, response rates to further chemotherapy are low and median survival is lower than 12 months. The complexity of platinum-resistant OC, which comprises a heterogeneous spectrum of diseases, is indeed far from being completely understood. Therefore, comprehending tumors' biological behaviour to identify reliable biomarkers, which may predict responses to therapies, is a demanding challenge to improve OC management. In the age of precision medicine, efforts to overcome platinum resistance in OC represent a dynamic and vast field in which innovative drugs and clinical trials rapidly develop. This review will present the exceptional biochemical environment implicated in OC and highlights mechanisms of chemoresistance. Furthermore, innovative molecules and new therapeutic opportunities are presented, along with currently available therapies and ongoing clinical trials.

The effectiveness of monotherapy with PI3K/AKT/mTOR pathway inhibitors in ovarian cancer: A meta-analysis

OBJECTIVE

To determine the clinical benefit of monotherapy with PI3K/AKT/mTOR inhibitors in patients diagnosed with advanced or recurrent ovarian cancer and to investigate the predictive value of current PI3K/AKT/mTOR biomarkers on therapy response.

METHODS

A systematic search was conducted in PubMed, Embase and the Cochrane Library for articles reporting on treatment with PI3K/AKT/mTOR inhibitors in ovarian cancer. The primary endpoint was defined as the clinical benefit rate (CBR), including the proportion of patients with complete (CR) and partial response (PR) and stable disease (SD). Secondary endpoints included the overall response rate (ORR, including CR and PR) and drug-related grade 3 and 4 adverse events.

RESULTS

We included 233 patients from 19 studies and observed a pooled CBR of 32% (95% CI 20-44%) and ORR of 3% (95% CI 0-6%) in advanced or recurrent ovarian cancer patients treated with PI3K/AKT/mTOR inhibitors. Subgroup analysis tended to favor the studies who selected patients based on current PI3K/AKT/mTOR biomarker criteria (e.g. genomic alterations or loss of PTEN protein expression), but the difference in CBR was not statistically significant from studies with unselected populations (respectively, CBR of 42% (95% CI 23-62%) and 27% (95% CI 14-42%), P = 0.217). To better reflect true patient benefit, we excluded SD <6 months as a beneficial outcome which resulted in a pooled CBR of 7% (95% CI 2-13%). The overall proportion of patients with drug-related grade 3 and 4 adverse events was 36%.

CONCLUSIONS

The efficacy of monotherapy with PI3K/AKT/mTOR inhibitors in advanced recurrent ovarian cancer patients is limited to a small subgroup and selection of patients with the use of current biomarkers did not improved the CBR significantly. Given the toxicity profile, we suggest that current treatment with PI3K/AKT/mTOR inhibitors should not be initiated unless in clinical trials. Furthermore, improved biomarkers to measure functional PI3K/AKT/mTOR pathway activity are needed to optimize patient selection.

Role of FOXO protein's abnormal activation through PI3K/AKT pathway in platinum resistance of ovarian cancer

AIM

Platinum-based chemotherapy is the standard treatment for ovarian cancer. However, tumor cells' resistance to platinum drugs often occurs. This paper provides a review of Forkhead box O (FOXO) protein's role in platinum resistance of ovarian cancer which hopefully may provide some further guidance for the treatment of platinum-resistant ovarian cancer.

METHODS

We reviewed a 128 published papers from authoritative and professional journals on FOXO and platinum-resistant ovarian cancer, and adopts qualitative analyses and interpretation based on the literature.

RESULTS

Ovarian cancer often has abnormal activation of cellular pathways, the most important of which is the PI3K/AKT pathway. FOXOs act as crucial downstream factor of the PI3K/Akt pathway and are negatively regulated by it. DNA damage response and apoptosis including the relationship between FOXOs and ATM-Chk2-p53 are essential for platinum resistance of ovarian cancer. Through gene expression analysis in platinum-resistant ovarian cancer cell model, it was found that FoxO-1 is decreased in platinum-resistant ovarian cancer, so studying the role of FOXO in the pathway on platinum-induced apoptosis may further guide the treatment of platinum-resistant ovarian cancer.

CONCLUSIONS

There are many drug resistance mechanisms in ovarian cancer, wherein the decrease in cancer cells apoptosis is one of the important causes. Constituted by a series of transcription factors evolving conservatively and mainly working in inhibiting cancer, FOXO proteins play various roles in cells' antitumor response. More and more evidence suggests that we need to re-understand the role that FOXOs have played in cancer development and treatment.

A bioinformatic analysis of the inhibin-betaglycan-endoglin/CD105 network reveals prognostic value in multiple solid tumors

Inhibins and activins are dimeric ligands belonging to the TGFβ superfamily with emergent roles in cancer. Inhibins contain an α-subunit (INHA) and a β-subunit (either INHBA or INHBB), while activins are mainly homodimers of either βA (INHBA) or βB (INHBB) subunits. Inhibins are biomarkers in a subset of cancers and utilize the coreceptors betaglycan (TGFBR3) and endoglin (ENG) for physiological or pathological outcomes. Given the array of prior reports on inhibin, activin and the coreceptors in cancer, this study aims to provide a comprehensive analysis, assessing their functional prognostic potential in cancer using a bioinformatics approach. We identify cancer cell lines and cancer types most dependent and impacted, which included p53 mutated breast and ovarian cancers and lung adenocarcinomas. Moreover, INHA itself was dependent on TGFBR3 and ENG/CD105 in multiple cancer types. INHA, INHBA, TGFBR3, and ENG also predicted patients' response to anthracycline and taxane therapy in luminal A breast cancers. We also obtained a gene signature model that could accurately classify 96.7% of the cases based on outcomes. Lastly, we cross-compared gene correlations revealing INHA dependency to TGFBR3 or ENG influencing different pathways themselves. These results suggest that inhibins are particularly important in a subset of cancers depending on the coreceptor TGFBR3 and ENG and are of substantial prognostic value, thereby warranting further investigation.

Pharmacologic inhibition of Akt in combination with chemotherapeutic agents effectively induces apoptosis in ovarian and endometrial cancer cell lines

The PI3K/Akt signaling pathway, the most frequently altered signaling system in human cancer, is a crucial inducer of dysregulated proliferation and neoplastic processes; however, few therapeutic strategies using PI3K/Akt inhibitors singly have been shown to be effective. The purpose of this paper was to underline the potential benefit of pharmacological modulation of the PI3K/Akt pathway when combined with specific chemotherapeutic regimens. We have studied the ability of NVP‐BEZ235 (PI3K/mTOR inhibitor) and AZD5363 (Akt inhibitor) in the sensitization of cancer cells to cisplatin and doxorubicin. Our results show that NVP‐BEZ235 sensitizes cells preferentially to cisplatin while AZD5363 sensitizes cells to doxorubicin. At equal concentrations (5 μm), both inhibitors reduce ribosomal protein S6 phosphorylation, but AZD5363 is more effective in reducing GSK3β phosphorylation as well as S6 phosphorylation. Additionally, AZD5363 is capable of inducing FOXO1 and p53 nuclear localization and reduces BAD phosphorylation, which is generally increased by cisplatin and doxorubicin. Finally, the combination of AZD5363 and doxorubicin induces apoptosis in cells and robustly reduces cell ability to clonally replicate, which underlines a potential cooperative effect of the studied compounds.