MAPK Activation Predicts Poor Outcome and the MEK Inhibitor, Selumetinib, Reverses Antiestrogen Resistance in ER-Positive High-Grade Serous Ovarian Cancer

Overview of BH3 mimetics in ovarian cancer

Ovarian carcinoma is the leading cause of gynecological cancer-related death, still with a dismal five-year prognosis, mainly due to late diagnosis and the emergence of resistance to cytotoxic and targeted agents. Bcl-2 family proteins have a key role in apoptosis and are associated with tumor development/progression and response to therapy in different cancer types, including ovarian carcinoma. In tumors, evasion of apoptosis is a possible mechanism of resistance to therapy. BH3 mimetics are small molecules that occupy the hydrophobic pocket on pro-survival proteins, allowing the induction of apoptosis, and are currently under study as single agents and/or in combination with cytotoxic and targeted agents in solid tumors. Here, we discuss recent advances in targeting anti-apoptotic proteins of the Bcl-2 family for the treatment of ovarian cancer, focusing on BH3 mimetics, and how these approaches could potentially offer an alternative/complementary way to treat patients and overcome or delay resistance to current treatments.

Advances in ovarian tumor stem cells and therapy

Ovarian cancer is considered the most lethal among all gynecological malignancies due to its early metastatic dissemination, extensive spread, and malignant ascites. The current standard of care for advanced ovarian cancer involves a combination of cytoreductive surgery and chemotherapy utilizing platinum-based and taxane-based agents. Although initial treatment yields clinical remission in 70-80% of patients, the majority eventually develop treatment resistance and tumor recurrence. A growing body of evidence indicates the existence of cancer stem cells within diverse solid tumors, including ovarian cancer, which function as a subpopulation to propel tumor growth and disease advancement by means of drug resistance, recurrence, and metastasis. The presence of ovarian cancer stem cells is widely considered to be a significant contributor to the unfavorable clinical outcomes observed in patients with ovarian cancer, as they play a crucial role in mediating chemotherapy resistance, recurrence, and metastasis. Ovarian cancer stem cells possess the capacity to reassemble within the entirety of the tumor following conventional treatment, thereby instigating the recurrence of ovarian cancer and inducing resistance to treatment. Consequently, the creation of therapeutic approaches aimed at eliminating ovarian cancer stem cells holds great potential for the management of ovarian cancer. These cells are regarded as one of the most auspicious targets and mechanisms for the treatment of ovarian cancer. There is a pressing need for a comprehensive comprehension of the fundamental mechanisms of ovarian cancer's recurrence, metastasis, and drug resistance, alongside the development of effective strategies to overcome chemoresistance, metastasis, and recurrence. The implementation of cancer stem cell therapies may potentially augment the tumor cells' sensitivity to existing chemotherapy protocols, thereby mitigating the risks of tumor metastasis and recurrence, and ultimately improving the survival rates of ovarian cancer patients.

The prognostic value of MEK pathway-associated estrogen receptor signaling activity for female cancers

BACKGROUND

Other than for breast cancer, endocrine therapy has not been highly effective for gynecologic cancers. Endocrine therapy resistance in estrogen receptor positive gynecologic cancers is still poorly understood. In this retrospective study, we examined the estrogen receptor (ER) signaling pathway activities of breast, ovarian, endometrial, and cervical cancers to identify those that may predict endocrine therapy responsiveness.

METHODS

Clinical and genomic data of women with breast and gynecological cancers were downloaded from cBioPortal for Cancer Genomics. Estrogen receptor alpha (ESR1) expression level and sample-level pathway enrichment scores (EERES) were calculated to classify patients into four groups (low/high ESR1 and low/high EERES). Correlation between ESR1/EERES score and survival was further validated with RNAseq data from low-grade serous ovarian cancer. Pathway analyses were performed among different ESR1/EERES groups to identify genes that correlate with endocrine resistance, which are validated using Cancer Cell Line Encyclopedia gene expression and Genomics of Drug Sensitivity in Cancer data.

RESULTS

We identified a novel combined prognostic value of ESR1 expression and the corresponding estrogen response signaling (EERES score) for breast cancer. The combined prognostic value (ESR1/EERES) may be applicable to other gynecologic cancers. More importantly, we discovered that ER signaling can cross-regulate MEK pathway activation. We identified downstream genes in the MEK pathway (EPHA2, INAVA, MALL, MPZL2, PCDH1, and TNFRSF21) that are potential endocrine therapy response biomarkers.

CONCLUSION

This study demonstrated that targeting both the ER and the ER signaling activity related MEK pathway may aid the development of endocrine therapy strategies for personalized medicine.

Advances in precision therapy of low-grade serous ovarian cancer: A review

Low-grade serous ovarian carcinoma (LGSOC) is a rare subtype of ovarian cancer that accounts for approximately 6% to 10% of serous ovarian cancers. The clinical treatment of LGSOC is similar to that of high-grade serous ovarian carcinoma, however, its clinical and molecular characteristics are different from those of high-grade serous ovarian carcinoma. This article reviews the research on gene diagnosis, surgical treatment, chemotherapy, and biological therapy of LGSOC, providing reference for clinical diagnosis and treatment of LGSOC. Surgery is the cornerstone of LGSOC treatment and maximum effort must be made to achieve R0 removal. Although LGSOC is not sensitive to chemotherapy, postoperative platinum-based combination chemotherapy remains the first-line treatment option for LGSOC. Additional clinical trials are needed to confirm the clinical benefits of chemotherapy and explore new chemotherapy protocols. Hormone and targeted therapies may also play important roles. Some patients, particularly those with residual lesions after treatment, may benefit from hormone maintenance therapy after chemotherapy. Targeted therapies, such as MEKi, show good application prospects and are expected to change the treatment pattern of LGSOC. Continuing to further study the genomics of LGSOC, identify its specific gene changes, and combine traditional treatment methods with precision targeted therapy based on second-generation sequencing may be the direction for LGSOC to overcome the treatment bottleneck. In future clinical work, comprehensive genetic testing should be carried out for LGSOC patients to accumulate data for future scientific research, in order to find more effective methods and drugs for the treatment of LGSOC.

Survey of NF1 inactivation by surrogate immunohistochemistry in ovarian carcinomas

OBJECTIVE

Inhibition of the MAPK pathway by MEK inhibitors (MEKi) is currently a therapeutic standard in several cancer types, including ovarian low-grade serous carcinoma (LGSC). A common MAPK pathway alteration in tubo-ovarian high-grade serous carcinoma (HGSC) is the genomic inactivation of neurofibromin 1 (NF1). The primary objectives of our study were to survey the prevalence of NF1 inactivation in the principal ovarian carcinoma histotype as well as to evaluate its associations with clinico-pathological parameters and key biomarkers including BRCA1/2 status in HGSC.

METHODS

A recently commercialized NF1 antibody (clone NFC) was orthogonally validated on an automated immunohistochemistry (IHC) platform and IHC was performed on tissue microarrays containing 2140 ovarian carcinoma cases. Expression was interpreted as loss/inactivated (complete or subclonal) versus normal/retained.

RESULTS

Loss of NF1 expression was detected in 250/1429 (17.4%) HGSC including 11% with subclonal loss. Survival of NF1-inactivated HGSC patients was intermediate between favorable BRCA1/2 mutated HGSC and unfavorable CCNE1 high-level amplified HGSC. NF1 inactivation was mutually exclusive with CCNE1 high-level amplifications, co-occurred with RB1 loss and occurred at similar frequencies in BRCA1/2 mutated versus wild-type HGSC. NF1 loss was found in 21/286 (7.3%) endometrioid carcinomas with a favorable prognostic association (p = 0.048), and in 4/64 (5.9%) LGSC, mutually exclusive with other driver events.

CONCLUSIONS

NF1 inactivation occurs in a significant subset of BRCA1/2 wild-type HGSC and a subset of LGSC. While the functional effects of NF1 inactivation need to be further characterized, this signifies a potential therapeutic opportunity to explore targeting NF1 inactivation in these tumors.

The potential of RAS/RAF/MEK/ERK (MAPK) signaling pathway inhibitors in ovarian cancer: A systematic review and meta-analysis

BACKGROUND

The RAS/RAF/MEK/ERK (MAPK) pathway plays a role in ovarian carcinogenesis. Low-grade serous ovarian carcinoma (LGSOC) frequently harbors activating MAPK mutations. MAPK inhibitors have been used in small subsets of ovarian carcinoma (OC) patients to control tumor growth. Therefore, we performed a meta-analysis to evaluate the effectiveness of MAPK inhibitors in OC patients. We aimed to determine the clinical benefit rate (CBR), the subgroup of MAPK inhibitors with the best CBR and overall response rate (ORR), and the most common adverse events.

METHODS

We conducted a search in PubMed, Embase via Ovid, the Cochrane library and clinicaltrials.gov on studies evaluating the efficacy of single MAPK pathway inhibition with MAPK pathway inhibitors in OC patients. Our primary outcome included the CBR, defined by the proportion of patients with stable disease (SD), complete (CR) and partial response (PR). Secondary outcomes included the ORR (including PR and CR) and grade 3 and 4 adverse events. Meta-analysis was performed using a random-effects model.

RESULTS

We included nine studies with a total of 319 OC patients, for which we determined a pooled CBR of 63% (95%-CI 39-84%, I² = 92%). Combined treatment with Raf- and MEK inhibitors in in BRAF^v600 mutated LGSOC (n = 6) had the greatest efficacy with a CBR of 100% and ORR of 83%. MEK inhibitors had the best efficacy as a single agent. Subgroup analysis by tumor histology demonstrated a significantly higher CBR and ORR in patients with LGSOC, with a pooled CBR and ORR of 87% (95%-CI 81-92%, I² = 0%) and 27% (95%-CI 10-48%, I² = 77%) respectively. Adverse events of grade 3 or higher were reported frequently: 123 in 167 patients.

CONCLUSIONS

MEK inhibitors are the most promising single agents in (LGS)OC. However, dual MAPK pathway inhibition should be considered in patients with a BRAF^v600 mutation, or non-mutated OC with depleted treatment options due indications of higher efficacy and tolerable toxicity profiles.

Kinase Inhibitors in the Treatment of Ovarian Cancer: Current State and Future Promises

Ovarian cancer is the deadliest gynecological cancer, the high-grade serous ovarian carcinoma (HGSC) being its most common and most aggressive form. Despite the latest therapeutical advancements following the introduction of vascular endothelial growth factor receptor (VEGFR) targeting angiogenesis inhibitors and poly-ADP-ribose-polymerase (PARP) inhibitors to supplement the standard platinum- and taxane-based chemotherapy, the expected overall survival of HGSC patients has not improved significantly from the five-year rate of 42%. This calls for the development and testing of more efficient treatment options. Many oncogenic kinase-signaling pathways are dysregulated in HGSC. Since small-molecule kinase inhibitors have revolutionized the treatment of many solid cancers due to the generality of the increased activation of protein kinases in carcinomas, it is reasonable to evaluate their potential against HGSC. Here, we present the latest concluded and on-going clinical trials on kinase inhibitors in HGSC, as well as the recent work concerning ovarian cancer patient organoids and xenograft models. We discuss the potential of kinase inhibitors as personalized treatments, which would require comprehensive assessment of the biological mechanisms underlying tumor spread and chemoresistance in individual patients, and their connection to tumor genome and transcriptome to establish identifiable subgroups of patients who are most likely to benefit from a given therapy.

Enhanced Therapeutic Effect of Optimized Melittin-dKLA, a Peptide Agent Targeting M2-like Tumor-Associated Macrophages in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is characterized by a high possibility of metastasis. M2-like tumor-associated macrophages (TAMs) are the main components of the tumor microenvironment (TME) and play a key role in TNBC metastasis. Therefore, TAMs may be a potential target for reducing TNBC metastasis. Melittin-dKLA, a peptide composed of fused melittin and pro-apoptotic peptide d(KLAKLAK)2 (dKLA), showed a potent therapeutic effect against cancers by depleting TAMs. However, melittin has a strong adverse hemolytic effect. Hence, we attempted to improve the therapeutic potential of melittin-dKLA by reducing toxicity and increasing stability. Nine truncated melittin fragments were synthesized and examined. Of the nine peptides, the melittin-dKLA8-26 showed the best binding properties to M2 macrophages and discriminated M0/M1/M2. All fragments, except melittin, lost their hemolytic effects. To increase the stability of the peptide, melittin-dKLA8-26 fragment was conjugated with PEGylation at the amino terminus and was named PEG-melittin-dKLA8-26. This final drug candidate was assessed in vivo in a murine TNBC model and showed superior effects on tumor growth, survival rates, and lung metastasis compared with the previously used melittin-dKLA. Taken together, our study showed that the novel PEG-melittin-dKLA8-26 possesses potential as a new drug for treating TNBC and TNBC-mediated metastasis by targeting TAMs.

Aberrant MAPK Signaling Offers Therapeutic Potential for Treatment of Ovarian Carcinoma

Ovarian cancer remains the most lethal gynecological malignancy worldwide due to lack of effective screening, vague early symptoms, poor description of biomarkers, and absence of effective treatment regimes. Epithelial ovarian carcinoma (EOC) is categorized into five distinct disease subtypes which collectively account for ~90% of ovarian carcinomas. Most women present at advanced stages contributing to a poor overall 5-year survival rate. Standard treatment for EOC is cytoreductive surgery and platinum-based chemotherapy; however, most patients suffer from recurrence and platinum-resistant disease, which highlights an urgent need for targeted therapy. The high frequency of molecular alterations affecting gain-of-function signaling through the RAS mitogen-activated protein kinase (MAPK) pathway in EOC has prompted pre-clinical and clinical efforts toward research into the effectiveness of MAPK pathway inhibition as a second-line treatment. The RAS/MAPK pathway is a highly conserved signal transduction cascade, often disrupted in cancer, that regulates tumorigenic phenotypes including cellular proliferation, survival, migration, apoptosis, and differentiation. Herein, the role of the MAPK pathway in EOC with emphasis on targetability of the pathway is described. Pre-clinical and clinical efforts to target MAPK signaling in EOC have identified several MAPK pathway inhibitors that offer efficacious potential for monotherapy and in combination with other compounds. Thus, inhibition of the RAS/MAPK pathway is emerging as a tractable strategy for treatment of ovarian cancer that may permit development of personalized therapy and improved prognosis for women challenged by this disease.

Optimized Transcriptional Signature for Evaluation of MEK/ERK Pathway Baseline Activity and Long-Term Modulations in Ovarian Cancer

Ovarian cancer is the most aggressive and lethal of all gynecologic malignancies. The high activity of the MEK/ERK signaling pathway is tightly associated with tumor growth, high recurrence rate, and treatment resistance. Several transcriptional signatures were proposed recently for evaluation of MEK/ERK activity in tumor tissue. In the present study, we validated the performance of a robust multi-cancer MPAS 10-gene signature in various experimental models and publicly available sets of ovarian cancer samples. Expression of four MPAS genes (PHLDA1, DUSP4, EPHA2, and SPRY4) displayed reproducible responses to MEK/ERK activity modulations across several experimental models in vitro and in vivo. Levels of PHLDA1, DUSP4, and EPHA2 expression were also significantly associated with baseline levels of MEK/ERK pathway activity in multiple human ovarian cancer cell lines and ovarian cancer patient samples available from the TCGA database. Initial platinum therapy resistance and advanced age at diagnosis were independently associated with poor overall patient survival. Taken together, our results demonstrate that the performance of transcriptional signatures is significantly affected by tissue specificity and aspects of particular experimental models. We therefore propose that gene expression signatures derived from comprehensive multi-cancer studies should be always validated for each cancer type.

Efficacy evaluation of multi-immunotherapy in ovarian cancer: From bench to bed

Ovarian cancer, one of the most common gynecological malignancies, is characterized by high mortality and poor prognosis. Cytoreductive surgery and chemotherapy remain the mainstay of ovarian cancer treatment, and most women experience recurrence after standard care therapies. There is compelling evidence that ovarian cancer is an immunogenic tumor. For example, the accumulation of tumor-infiltrating lymphocytes is associated with increased survival, while increases in immunosuppressive regulatory T cells are correlated with poor clinical outcomes. Therefore, immunotherapies targeting components of the tumor microenvironment have been gradually integrated into the existing treatment options, including immune checkpoint blockade, adoptive cell therapy, and cancer vaccines. Immunotherapies have changed guidelines for maintenance treatment and established a new paradigm in ovarian cancer treatment. Despite single immunotherapies targeting DNA repair mechanisms, immune checkpoints, and angiogenesis bringing inspiring efficacy, only a subset of patients can benefit much from it. Thus, the multi-immunotherapy investigation remains an active area for ovarian cancer treatment. The current review provides an overview of various clinically oriented forms of multi-immunotherapy and explores potentially effective combinational therapies for ovarian cancer.

A kinase inhibitor screen reveals MEK1/2 as a novel therapeutic target to antagonize IGF1R-mediated antiestrogen resistance in ERα-positive luminal breast cancer

Antiestrogen resistance of breast cancer has been related to enhanced growth factor receptor expression and activation. We have previously shown that ectopic expression and subsequent activation of the insulin-like growth factor-1 receptor (IGF1R) or the epidermal growth factor receptor (EGFR) in MCF7 or T47D breast cancer cells results in antiestrogen resistance. In order to identify novel therapeutic targets to prevent this antiestrogen resistance, we performed kinase inhibitor screens with 273 different inhibitors in MCF7 cells overexpressing IGF1R or EGFR. Kinase inhibitors that antagonized antiestrogen resistance but are not directly involved in IGF1R or EGFR signaling were prioritized for further analyses. Various ALK (anaplastic lymphoma receptor tyrosine kinase) inhibitors inhibited cell proliferation in IGF1R expressing cells under normal and antiestrogen resistance conditions by preventing IGF1R activation and subsequent downstream signaling; the ALK inhibitors did not affect EGFR signaling. On the other hand, MEK (mitogen-activated protein kinase kinase)1/2 inhibitors, including PD0325901, selumetinib, trametinib and TAK733, selectively antagonized IGF1R signaling-mediated antiestrogen resistance but did not affect cell proliferation under normal growth conditions. RNAseq analysis revealed that MEK inhibitors PD0325901 and selumetinib drastically altered cell cycle progression and cell migration networks under IGF1R signaling-mediated antiestrogen resistance. In a group of 219 patients with metastasized ER+ breast cancer, strong pMEK staining showed a significant correlation with no clinical benefit of first-line tamoxifen treatment. We propose a critical role for MEK activation in IGF1R signaling-mediated antiestrogen resistance and anticipate that dual-targeted therapy with a MEK inhibitor and antiestrogen could improve treatment outcome.

Applications of Proteomics in Ovarian Cancer: Dawn of a New Era

The ability to identify ovarian cancer (OC) at its earliest stages remains a challenge. The patients present an advanced stage at diagnosis. This heterogeneous disease has distinguishable etiology and molecular biology. Next-generation sequencing changed clinical diagnostic testing, allowing assessment of multiple genes, simultaneously, in a faster and cheaper manner than sequential single gene analysis. Technologies of proteomics, such as mass spectrometry (MS) and protein array analysis, have advanced the dissection of the underlying molecular signaling events and the proteomic characterization of OC. Proteomics analysis of OC, as well as their adaptive responses to therapy, can uncover new therapeutic choices, which can reduce the emergence of drug resistance and potentially improve patient outcomes. There is an urgent need to better understand how the genomic and epigenomic heterogeneity intrinsic to OC is reflected at the protein level, and how this information could potentially lead to prolonged survival.

Four Types of RNA Modification Writer-Related lncRNAs Are Effective Predictors of Prognosis and Immunotherapy Response in Serous Ovarian Carcinoma

Serous ovarian carcinoma (SOC) is a gynecological malignancy with high mortality rates. Currently, there is a lack of reliable biomarkers for accurate SOC patient prognosis. Here, we analyzed SOC RNA-Seq data from The Cancer Genome Atlas (TCGA) to identify prognostic biomarkers. Through the pearson correlation analysis, univariate Cox regression analysis, and LASSO-penalized Cox regression analysis, we identified nine lncRNAs significantly associated with four types of RNA modification writers (m6A, m1A, APA, and A-I) and with the prognosis of SOC patients (P <0.05). Six writer-related lncRNAs were ultimately selected following multivariate Cox analysis. We established a risk prediction model based on these six lncRNAs and evaluated its prognostic value in multiple groups (training set, testing set, and entire set). Our risk prediction model could effectively predict the prognosis of SOC patients with different clinical characteristics and their responses to immunotherapy. Lastly, we validated the predictive reliability and sensitivity of the lncRNA-based model via a nomogram. This study explored the association between RNA modification writer-related lncRNAs and SOC prognosis, providing a potential complement for the clinical management of SOC patients.

Trametinib versus standard of care in patients with recurrent low-grade serous ovarian cancer (GOG 281/LOGS): an international, randomised, open-label, multicentre, phase 2/3 trial

BACKGROUND

Low-grade serous carcinoma of the ovary or peritoneum is characterised by MAPK pathway aberrations and its reduced sensitivity to chemotherapy relative to high-grade serous carcinoma. We compared the MEK inhibitor trametinib to physician's choice standard of care in patients with recurrent low-grade serous carcinoma.

METHODS

This international, randomised, open-label, multicentre, phase 2/3 trial was done at 84 hospitals in the USA and UK. Eligible patients were aged 18 years or older with recurrent low-grade serous carcinoma and measurable disease, as defined by Response Evaluation Criteria In Solid Tumors version 1.1, had received at least one platinum-based regimen, but not all five standard-of-care drugs, and had received an unlimited number of previous regimens. Patients with serous borderline tumours or tumours containing low-grade serous and high-grade serous carcinoma were excluded. Eligible patients were randomly assigned (1:1) to receive either oral trametinib 2 mg once daily (trametinib group) or one of five standard-of-care treatment options (standard-of-care group): intravenous paclitaxel 80 mg/m2 by body surface area on days 1, 8, and 15 of every 28-day cycle; intravenous pegylated liposomal doxorubicin 40-50 mg/m2 by body surface area once every 4 weeks; intravenous topotecan 4 mg/m2 by body surface area on days 1, 8, and 15 of every 28-day cycle; oral letrozole 2·5 mg once daily; or oral tamoxifen 20 mg twice daily. Randomisation was stratified by geographical region (USA or UK), number of previous regimens (1, 2, or ≥3), performance status (0 or 1), and planned standard-of-care regimen. The primary endpoint was investigator-assessed progression-free survival while receiving randomised therapy, as assessed by imaging at baseline, once every 8 weeks for 15 months, and then once every 3 months thereafter, in the intention-to-treat population. Safety was assessed in patients who received at least one dose of study therapy. This trial is registered with ClinicalTrials.gov, NCT02101788, and is active but not recruiting.

FINDINGS

Between Feb 27, 2014, and April 10, 2018, 260 patients were enrolled and randomly assigned to the trametinib group (n=130) or the standard-of-care group (n=130). At the primary analysis, there were 217 progression-free survival events (101 [78%] in the trametinib group and 116 [89%] in the standard-of-care group). Median progression-free survival in the trametinib group was 13·0 months (95% CI 9·9-15·0) compared with 7·2 months (5·6-9·9) in the standard-of-care group (hazard ratio 0·48 [95% CI 0·36-0·64]; p<0·0001). The most frequent grade 3 or 4 adverse events in the trametinib group were skin rash (17 [13%] of 128), anaemia (16 [13%]), hypertension (15 [12%]), diarrhoea (13 [10%]), nausea (12 [9%]), and fatigue (ten [8%]). The most frequent grade 3 or 4 adverse events in the standard-of-care group were abdominal pain (22 [17%]), nausea (14 [11%]), anaemia (12 [10%]), and vomiting (ten [8%]). There were no treatment-related deaths.

INTERPRETATION

Trametinib represents a new standard-of-care option for patients with recurrent low-grade serous carcinoma.

FUNDING

NRG Oncology, Cancer Research UK, Target Ovarian Cancer, and Novartis.

The Clinical Challenges, Trials, and Errors of Combatting Poly(ADP-Ribose) Polymerase Inhibitors Resistance

ABSTRACT

The use of poly(ADP-ribose) polymerase inhibitor (PARPi) exploits synthetic lethality in solid tumors with homologous recombination repair (HRR) defects. Significant clinical benefit has been established in breast and ovarian cancers harboring BRCA1/2 mutations, as well as tumors harboring characteristics of "BRCAness." However, the durability of treatment responses is limited, and emerging data have demonstrated the clinical challenge of PARPi resistance. With the expanding use of PARPi, the significance of PARP therapy in patients pretreated with PARPi remains in need of significant further investigation. Molecular mechanisms contributing to this phenomenon include restoration of HRR function, replication fork stabilization, BRCA1/2 reversion mutations, and epigenetic changes. Current studies are evaluating the utility of combination therapies of PARPi with cell cycle checkpoint inhibitors, antiangiogenic agents, phosphatidylinositol 3-kinase/AKT pathway inhibitors, MEK inhibitors, and epigenetic modifiers to overcome this resistance. In this review, we address the mechanisms of PARPi resistance supported by preclinical models, examine current clinical trials applying combination therapy to overcome PARPi resistance, and discuss future directions to enhance the clinical efficacy of PARPi.

The evolving role of PARP inhibitors in advanced ovarian cancer

The field of ovarian cancer has been revolutionized with the use of poly (ADP-ribose) polymerase (PARP) inhibitors, which present greater inhibition effect in epithelial subtype due to high rates of homologous recombination deficiency. PARP inhibition exploits this cancer pitfall by disrupting DNA repair, leading to genomic instability and apoptosis. Three PARP inhibitors (olaparib, niraparib, and rucaparib) are now approved for use in women with epithelial ovarian cancer, while others are under development. Among women with BRCA1/2 mutations, maintenance PARP therapy has led to a nearly fourfold prolongation of PFS, while those without BRCA1/2 mutations experience an approximately twofold increase in PFS. Differences in trial design, patient selection and primary analysis population affect the conclusions on PARP inhibitors. Limited OS data have been published and there is also limited experience regarding long-term safety. With regard to toxicity profile, there are no differences in serious adverse events between the experimental and control groups. However, combining adverse event data from maintenance phases, a trend towards more events in the experimental group, compared with controls, has been shown. The mechanisms of PARP-inhibitor resistance include restoration of HR through reversion mutations in HR genes, leading to resumed HR function. Other mechanisms that sustain sufficient DNA repair are discussed as well. PARP inhibitors play a pivotal role in the management of ovarian cancer, affecting the future treatment choices. Defining exactly which patients will benefit from them is a challenge and the need for HRD testing to define ‘BRCA-ness’ will add additional costs to treatment.

MicroRNAs as the critical regulators of cisplatin resistance in gastric tumor cells

Combined chemotherapeutic treatment is the method of choice for advanced and metastatic gastric tumors. However, resistance to chemotherapeutic agents is one of the main challenges for the efficient gastric cancer (GC) treatment. Cisplatin (CDDP) is used as an important regimen of chemotherapy for GC which induces cytotoxicity by interfering with DNA replication in cancer cells and inducing their apoptosis. Majority of patients experience cisplatin-resistance which is correlated with tumor metastasis and relapse. Moreover, prolonged and high-dose cisplatin administrations cause serious side effects such as nephrotoxicity, ototoxicity, and anemia. Since, there is a high rate of recurrence after CDDP treatment in GC patients; it is required to clarify the molecular mechanisms associated with CDDP resistance to introduce novel therapeutic methods. There are various cell and molecular processes associated with multidrug resistance (MDR) including drug efflux, detoxification, DNA repair ability, apoptosis alteration, signaling pathways, and epithelial-mesenchymal transition (EMT). MicroRNAs are a class of endogenous non-coding RNAs involved in chemo resistance of GC cells through regulation of all of the MDR mechanisms. In present review we have summarized all of the miRNAs associated with cisplatin resistance based on their target genes and molecular mechanisms in gastric tumor cells. This review paves the way of introducing a miRNA-based panel of prognostic markers to improve the efficacy of chemotherapy and clinical outcomes in GC patients. It was observed that miRNAs are mainly involved in cisplatin response of gastric tumor cells via regulation of signaling pathways, autophagy, and apoptosis.

The MEK1/2 Pathway as a Therapeutic Target in High-Grade Serous Ovarian Carcinoma

High-grade serous ovarian carcinoma (HGSOC) is the deadliest of gynecological cancers due to its high recurrence rate and acquired chemoresistance. RAS/MEK/ERK pathway activation is linked to cell proliferation and therapeutic resistance, but the role of MEK1/2-ERK1/2 pathway in HGSOC is poorly investigated. We evaluated MEK1/2 pathway activity in clinical HGSOC samples and ovarian cancer cell lines using immunohistochemistry, immunoblotting, and RT-qPCR. HGSOC cell lines were used to assess immediate and lasting effects of MEK1/2 inhibition with trametinib in vitro. Trametinib effect on tumor growth in vivo was investigated using mouse xenografts. MEK1/2 pathway is hyperactivated in HGSOC and is further stimulated by cisplatin treatment. Trametinib treatment causes cell cycle arrest in G1/0-phase and reduces tumor growth rate in vivo but does not induce cell death or reduce fraction of CD133+ stem-like cells, while increasing expression of stemness-associated genes instead. Transient trametinib treatment causes long-term increase in a subpopulation of cells with high aldehyde dehydrogenase (ALDH)1 activity that can survive and grow in non-adherent conditions. We conclude that MEK1/2 inhibition may be a promising approach to suppress ovarian cancer growth as a maintenance therapy. Promotion of stem-like properties upon MEK1/2 inhibition suggests a possible mechanism of resistance, so a combination with CSC-targeting drugs should be considered.

Integrated molecular characterisation of the MAPK pathways in human cancers reveals pharmacologically vulnerable mutations and gene dependencies

The mitogen-activated protein kinase (MAPK) pathways are crucial regulators of the cellular processes that fuel the malignant transformation of normal cells. The molecular aberrations which lead to cancer involve mutations in, and transcription variations of, various MAPK pathway genes. Here, we examine the genome sequences of 40,848 patient-derived tumours representing 101 distinct human cancers to identify cancer-associated mutations in MAPK signalling pathway genes. We show that patients with tumours that have mutations within genes of the ERK-1/2 pathway, the p38 pathways, or multiple MAPK pathway modules, tend to have worse disease outcomes than patients with tumours that have no mutations within the MAPK pathways genes. Furthermore, by integrating information extracted from various large-scale molecular datasets, we expose the relationship between the fitness of cancer cells after CRISPR mediated gene knockout of MAPK pathway genes, and their dose-responses to MAPK pathway inhibitors. Besides providing new insights into MAPK pathways, we unearth vulnerabilities in specific pathway genes that are reflected in the re sponses of cancer cells to MAPK targeting drugs: a revelation with great potential for guiding the development of innovative therapies.

Oncogenic mutation in RAS-RAF axis leads to increased expression of GREB1, resulting in tumor proliferation in colorectal cancer

BRAF^V600E mutation accounts for up to 90% of all BRAF mutations in human colorectal cancer (CRC), and constitutively activates the MEK‐MAPK pathway. It is recognized that neutralizing mAbs for epidermal growth factor receptor alone are not effective for CRC with BRAF^V600E mutation. Therefore, there is increasing interest in identification of the possible therapeutic targets in downstream of BRAF mutation in CRCs. To address this, we studied genome engineered mouse models for colonic neoplasia that has Braf^V600E mutation on the basis of Apc inactivation, induced in 2 distinct Cre mouse models, CDX2P‐G22Cre and CDX2P‐CreER^T2 mice. We carried out oligonucleotide microarray analysis for colonic neoplasia generated in these mouse models, and compared gene expression profiles among Kras/Braf WT, Kras‐mutated, and Braf‐mutated mouse colon tumors to seek new molecular targets corresponding to the KRAS‐BRAF‐MAPK axis. We found that the expression of the growth regulation by estrogen in breast cancer protein 1 (Greb1) was the most upregulated gene in Braf‐mutated mouse tumors compared to Kras/Braf WT counterparts. The silencing of GREB1 significantly reduced the proliferation and tumorigenesis of CRC cell lines, whereas the overexpression of GREB1 promoted cell proliferation. Although GREB1 was first identified as a hormone‐responsive gene mediating estrogen‐stimulated cell proliferation in endometriosis, breast, and ovarian cancers, these results suggest that RAS‐RAF‐MAPK signaling upregulates GREB1 expression in CRC, resulting in cellular proliferation. Thus, GREB1 is a possible therapeutic target for CRCs with Braf^V600E mutation.

Therapeutic efficacy of liposomal Grb2 antisense oligodeoxynucleotide (L-Grb2) in preclinical models of ovarian and uterine cancer

BACKGROUND

Adaptor proteins such as growth factor receptor-bound protein-2 (Grb2) play important roles in cancer cell signaling. In the present study, we examined the biological effects of liposomal antisense oligodeoxynucleotide that blocks Grb2 expression (L-Grb2) in gynecologic cancer models.

MATERIALS AND METHODS

Murine orthotopic models of ovarian (OVCAR5 and SKOV3ip1) and uterine (Hec1a) cancer were used to study the biological effects of L-Grb2 on tumor growth. In vitro experiments (cell viability assay, Western blot analysis, siRNA transfection, and reverse phase protein array) were carried out to elucidate the mechanisms and potential predictors of tumor response to L-Grb2.

FINDINGS

Treatment with L-Grb2 decreased tumor growth and metastasis in orthotopic models of ovarian cancer (OVCAR5, SKOV3ip1) by reducing angiogenesis and increasing apoptosis at a dose of 15 mg/kg with no effect on mouse body weight. Treatment with L-Grb2 and paclitaxel led to the greatest decrease in tumor weight (mean ± SEM, 0.17 g ± 0.10 g) compared with that in control mice (0.99 g ± 0.35 g). We also observed a reduction in tumor burden after treatment with L-Grb2 and the anti-VEGF antibody B-20 (86% decrease in tumor weight compared with that in controls). Ovarian cancer cells with ErbB2 amplification (OVCAR8 and SKOV3ip1) were the most sensitive to Grb2 downregulation. Reverse phase protein array analysis identified significant dysregulation of metabolites (LDHA, GAPDH, and TCA intermediates) in ovarian cancer cells after Grb2 downregulation.

INTERPRETATION

L-Grb2 has therapeutic efficacy in preclinical models of ovarian and uterine cancer. These findings support further clinical development of L-Grb2.

Dual Fulvestrant-Trametinib Therapy in Recurrent Low-Grade Serous Ovarian Cancer

Low-grade serous ovarian carcinoma (LGSOC) is known to exhibit chemoresistance. Effective treatment options for recurrent disease are few and often limited to hormone antagonism. Combination of endocrine therapies with MEK-inhibitors displays synergism in preclinical ovarian cancer models, however. This brief communication presents the use of combination anti-estrogenic and MEK-inhibitor therapies, fulvestrant and trametinib, as treatment in a heavily pretreated patient with estrogen receptor-positive, recurrent LGSOC. The dual-therapy regimen was well tolerated and appeared to confer 9 months of progression-free survival. Further investigation is warranted to explore this effect.

PI3K pathway protein analyses in metastatic breast cancer patients receiving standard everolimus and exemestane

Purpose

Everolimus plus exemestane (EVE/EXE) is a registered treatment option for ER-positive, HER2-negative (ER +/HER2-) metastatic breast cancer (MBC), but resistance mechanisms limit efficacy. We aimed to find markers that might help select patients with a higher chance on benefit from EVE/EXE.

Methods

Immunohistochemistry (IHC) of PTEN, p-AKT(Thr308), p-AKT(Ser473), p-4EBP1, p-p70S6K, p-S6RP(Ser240/244), p-ERK1/2 and p-S6RP (Ser235/236) was performed on primary tumour tissue and on biopsies immediately taken from ER +/HER2- MBC patients before the start of standard EVE/EXE (Eudract 2013-004120-11). Unsupervised hierarchical clustering was executed to create heatmaps to distinguish subgroups of preferentially activated and less-activated PI3K/MAPK proteins. Uni- and multivariate Cox models were used for associations with PFS.

Results

Primary tumour tissue from 145 patients was retrieved. Median PFS was 5.4 months. Patients without (neo)adjuvant therapy (p = 0.03) or bone only disease (p = 0.04) had longer PFS on EVE/EXE. In primary tumours, neither single proteins nor PI3K/MAPK-associated heatmap subgroups were significantly associated with PFS. In 21 patients a non-osseous biopsy obtained before dosing was useful for continuous scoring, which demonstrated upregulation of several proteins as compared to readings in corresponding primary tumour tissues. These comparisons revealed that increased expression of p-4EBP1 was significantly associated with worse PFS (multivariate HR 3.69, p = 0.05).

Conclusions

IHC of single proteins or heatmap subgroups of the differentially activated PI3K/MAPK pathways was not able to discriminate patients on EVE/EXE with poor or better PFS. Upregulation of p-4EBP1 in pre-treatment biopsies as compared to levels in primary tumours pointed towards shorter PFS.

Electronic supplementary material

The online version of this article (10.1007/s00432-020-03291-x) contains supplementary material, which is available to authorized users.

Overexpression of BMPER in Ovarian Cancer and the Mechanism by which It Promotes Malignant Biological Behavior in Tumor Cells

Background

BMPER has been reported to be associated with the biological behavior of a few malignant tumors, but the mechanism is still unclear. We aimed to detect BMPER expression in ovarian epithelial tumor tissues and its effects on their biological behaviors, as well as to elucidate the possible mechanism.

Methods

BMPER expression in ovarian epithelial tumor tissues was detected by immunohistochemistry. BMPER expression in ovarian cancer cell lines was inhibited via RNA interference. Changes in the malignant behaviors of ovarian cancer cells were detected by MTT, wound healing, Transwell, and flow cytometry assays. Changes in proteins in the MAPK and autophagy-related signaling pathways were detected by Western blot analysis.

Results

The expression of BMPER was significantly upregulated in ovarian epithelial malignant tumors and was related to increased lymph node metastasis and lower survival rate. High BMPER expression is an independent risk factor for poor prognosis in patients. Inhibition of BMPER inhibited the proliferation, invasion, and migration of ovarian cancer cells and promoted apoptosis. In addition, BMPER downregulation decreased the expression of PCNA, Bcl-2, MMP2, and MMP9 and increased the expression of Bax. Moreover, the levels of p-ERK, p-MEK, and the autophagy-related protein p-mTOR were decreased, and Beclin 1 levels and the LC3II/I ratio were increased.

Conclusions

Our findings indicated that BMPER is closely related to poor prognosis in ovarian cancer. BMPER plays a role in promoting the malignant biological behavior of tumor cells through the MAPK and autophagy-related signaling pathways.

Metabolic gene alterations impact the clinical aggressiveness and drug responses of 32 human cancers

Malignant cells reconfigure their metabolism to support oncogenic processes such as accelerated growth and proliferation. The mechanisms by which this occurs likely involve alterations to genes that encode metabolic enzymes. Here, using genomics data for 10,528 tumours of 32 different cancer types, we characterise the alterations of genes involved in various metabolic pathways. We find that mutations and copy number variations of metabolic genes are pervasive across all human cancers. Based on the frequencies of metabolic gene alterations, we further find that there are two distinct cancer supertypes that tend to be associated with different clinical outcomes. By utilising the known dose-response profiles of 825 cancer cell lines, we infer that cancers belonging to these supertypes are likely to respond differently to various anticancer drugs. Collectively our analyses define the foundational metabolic features of different cancer supertypes and subtypes upon which discriminatory strategies for treating particular tumours could be constructed.

Proteomics advances for precision therapy in ovarian cancer

Introduction: Due to the relatively low mutation rate and high frequency of copy number variation, finding actionable genetic drivers of high-grade serous carcinoma (HGSC) is a challenging task. Furthermore, emerging studies show that genetic alterations are frequently poorly represented at the protein level adding a layer of complexity. With improvements in large-scale proteomic technologies, proteomics studies have the potential to provide robust analysis of the pathways driving high HGSC behavior. Areas covered: This review summarizes recent large-scale proteomics findings across adequately sized ovarian cancer sample sets. Key words combined with 'ovarian cancer' including 'proteomics', 'proteogenomic', 'reverse-phase protein array', 'mass spectrometry', and 'adaptive response', were used to search PubMed. Expert opinion: Proteomics analysis of HGSC as well as their adaptive responses to therapy can uncover new therapeutic liabilities, which can reduce the emergence of drug resistance and potentially improve patient outcomes. There is a pressing need to better understand how the genomic and epigenomic heterogeneity intrinsic to ovarian cancer is reflected at the protein level and how this information could be used to improve patient outcomes.

Differential Activation of ERK Signaling in HPV-Related Oropharyngeal Squamous Cell Carcinoma

Human papillomavirus (HPV)-related oropharyngeal squamous cell carcinoma (OPSCC) forms a distinct tumor entity with better survival clinical outcome. Numerous underlying molecular mechanisms have been postulated for differences in treatment response, but the impact of MEK/ERK signaling, a main driver of carcinogenesis in various cancers including OPSCC and key player mediating therapy resistance remains elusive. In a retrospective experimental cohort study, primary tumor samples from OPSCC patients (n = 124) were available on tissue microarrays (TMAs) and expression levels of phosphorylated ERK1/2 (pERK1/2) were detected by immunohistochemical staining. Correlations of pERK1/2 expression patterns with clinicopathological features and clinical outcome were evaluated by statistical analysis. A low pERK1/2 expression was strongly associated with HPV-related OPSCC, while primary tumors with high pERK1/2 staining showed a distinctly worse survival outcome and were associated with higher cellular differentiation. Co-activation of both ERK1/2 and AKT was a common event and was associated with unfavorable prognosis in our cohort. However, the combinatorial analysis of pAKT (Ser473) and pERK1/2 did not strengthen the predictive power of pERK1/2, suggesting that pERK1/2 plays a more significant function in OPSCC. In summary, our data provide a compelling experimental and statistical evidence that low levels of tumor cell intrinsic ERK1/2 activation contribute at least in part to the favorable outcome of HPV-related OPSCC. On the other hand, presented findings indicate that non-HPV-related OPSCC with elevated ERK phosphorylation are at high risk for treatment failure and might benefit from targeted therapy of MEK/ERK signaling.

Exosomal miRNAs as Novel Pharmacodynamic Biomarkers for Cancer Chemopreventive Agent Early Stage Treatments in Chemically Induced Mouse Model of Lung Squamous Cell Carcinoma

Background: Chemopreventive agent (CPA) treatment is one of the main preventive options for lung cancer. However, few studies have been done on pharmacodynamic biomarkers of known CPAs for lung cancer. Materials and methods: In this study, we treated mouse models of lung squamous cell carcinoma with three different CPAs (MEK inhibitor: AZD6244, PI-3K inhibitor: XL-147 and glucocorticoid: Budesonide) and examined circulating exosomal miRNAs in the plasma of each mouse before and after treatment. Results: Compared to baselines, we found differentially expressed exosomal miRNAs after AZD6244 treatment (n = 8, FDR < 0.05; n = 55, raw p-values < 0.05), after XL-147 treatment (n = 4, FDR < 0.05; n = 26, raw p-values < 0.05) and after Budesonide treatment (n = 1, FDR < 0.05; n = 36, raw p-values < 0.05). In co-expression analysis, we found that modules of exosomal miRNAs reacted to CPA treatments differently. By variable selection, we identified 11, 9 and nine exosomal miRNAs as predictors for AZD6244, XL-147 and Budesonide treatment, respectively. Integrating all the results, we highlighted 4 miRNAs (mmu-miR-215-5p, mmu-miR-204-5p, mmu-miR-708-3p and mmu-miR-1298-5p) as the key for AZD6244 treatment, mmu-miR-23a-3p as key for XL-147 treatment, and mmu-miR-125a-5p and mmu-miR-16-5p as key for Budesonide treatment. Conclusions: This is the first study to use circulating exosomal miRNAs as pharmacodynamic biomarkers for CPA treatment in lung cancer.

Combined MEK and BCL-2/XL Inhibition Is Effective in High-Grade Serous Ovarian Cancer Patient-Derived Xenograft Models and BIM Levels Are Predictive of Responsiveness

Most patients with late-stage high-grade serous ovarian cancer (HGSOC) initially respond to chemotherapy but inevitably relapse and develop resistance, highlighting the need for novel therapies to improve patient outcomes. The MEK/ERK pathway is activated in a large subset of HGSOC, making it an attractive therapeutic target. Here, we systematically evaluated the extent of MEK/ERK pathway activation and efficacy of pathway inhibition in a large panel of well-annotated HGSOC patient-derived xenograft models. The vast majority of models were nonresponsive to the MEK inhibitor cobimetinib (GDC-0973) despite effective pathway inhibition. Proteomic analyses of adaptive responses to GDC-0973 revealed that GDC-0973 upregulated the proapoptotic protein BIM, thus priming the cells for apoptosis regulated by BCL2-family proteins. Indeed, combination of both MEK inhibitor and dual BCL-2/XL inhibitor (ABT-263) significantly reduced cell number, increased cell death, and displayed synergy in vitro in most models. In vivo, GDC-0973 and ABT-263 combination was well tolerated and resulted in greater tumor growth inhibition than single agents. Detailed proteomic and correlation analyses identified two subsets of responsive models-those with high BIM at baseline that was increased with MEK inhibition and those with low basal BIM and high pERK levels. Models with low BIM and low pERK were nonresponsive. Our findings demonstrate that combined MEK and BCL-2/XL inhibition has therapeutic activity in HGSOC models and provide a mechanistic rationale for the clinical evaluation of this drug combination as well as the assessment of the extent to which BIM and/or pERK levels predict drug combination effectiveness in chemoresistant HGSOC.

Using Reverse Phase Protein Array (RPPA) to Identify and Target Adaptive Resistance

Tumor cells and the tumor ecosystem rapidly evolve in response to therapy. This tumor evolution results in the rapid emergence of drug resistance that limits the magnitude and duration of response to therapy including chemotherapy, targeted therapy, and immunotherapy. Thus, there is an urgent need to understand and interdict tumor evolution to improve patient benefit to therapy. Reverse phase protein array (RPPA) provides a powerful tool to evaluate and develop approaches to target the processes underlying one form of tumor evolution: adaptive evolution. Tumor cells and the tumor microenvironment rapidly evolve through rewiring of protein networks to bypass the effects of therapy. In this review, we present the concepts underlying adaptive resistance and use of RPPA in understanding resistance mechanisms and identification of effective drug combinations. We further demonstrate that this novel information is resulting in biomarker-driven trials aimed at targeting adaptive resistance and improving patient outcomes.

Molecular subtyping of cancer and nomination of kinase candidates for inhibition with phosphoproteomics: Reanalysis of CPTAC ovarian cancer

Background

Molecular subtyping of cancer aimed to predict patient overall survival (OS) and nominate drug targets for patient treatments is central to precision oncology. Owing to the rapid development of phosphoproteomics, we can now measure thousands of phosphoproteins in human cancer tissues. However, limited studies report how to analyse the complex phosphoproteomic data for cancer subtyping and to nominate druggable kinase candidates.

Findings

In this work, we reanalysed the phosphoproteomic data of high-grade serous ovarian cancer (HGSOC) from the Clinical Proteomic Tumour Analysis Consortium (CPTAC). Our analysis classified HGSOC into 5 major subtypes that were associated with different OS and appeared to be more accurate than that achieved with protein profiling. We provided a workflow to identify 29 kinases whose increased activities in tumours are associated with poor survival. The altered kinase signalling landscape of HGSOC included the PI3K/AKT/mTOR, cell cycle and MAP kinase signalling pathways. We also developed a “patient-specific” hierarchy of clinically actionable kinases and selected kinase inhibitors by considering kinase activation and kinase inhibitor selectivity.

Interpretation

Our study offered a global phosphoproteomics data analysis workflow to aid in cancer molecular subtyping, determining phosphorylation-based cancer hallmarks and facilitating nomination of kinase inhibition in cancer.

Dual Src and MEK Inhibition Decreases Ovarian Cancer Growth and Targets Tumor Initiating Stem-Like Cells

Purpose: Rational targeted therapies are needed for treatment of ovarian cancers. Signaling kinases Src and MAPK are activated in high-grade serous ovarian cancer (HGSOC). Here, we tested the frequency of activation of both kinases in HGSOC and the therapeutic potential of dual kinase inhibition.Experimental Design: MEK and Src activation was assayed in primary HGSOC from The Cancer Genome Atlas (TGGA). Effects of dual kinase inhibition were assayed on cell-cycle, apoptosis, gene, and proteomic analysis; cancer stem cells; and xenografts.Results: Both Src and MAPK are coactivated in 31% of HGSOC, and this associates with worse overall survival on multivariate analysis. Frequent dual kinase activation in HGSOC led us to assay the efficacy of combined Src and MEK inhibition. Treatment of established lines and primary ovarian cancer cultures with Src and MEK inhibitors saracatinib and selumetinib, respectively, showed target kinase inhibition and synergistic induction of apoptosis and cell-cycle arrest in vitro, and tumor inhibition in xenografts. Gene expression and proteomic analysis confirmed cell-cycle inhibition and autophagy. Dual therapy also potently inhibited tumor-initiating cells. Src and MAPK were both activated in tumor-initiating populations. Combination treatment followed by drug washout decreased sphere formation and ALDH1+ cells. In vivo, tumors dissociated after dual therapy showed a marked decrease in ALDH1 staining, sphere formation, and loss of tumor-initiating cells upon serial xenografting.Conclusions: Selumetinib added to saracatinib overcomes EGFR/HER2/ERBB2-mediated bypass activation of MEK/MAPK observed with saracatinib alone and targets tumor-initiating ovarian cancer populations, supporting further evaluation of combined Src-MEK inhibition in clinical trials. Clin Cancer Res; 24(19); 4874-86. ©2018 AACR.

Establishment and Characterization of the Novel High-Grade Serous Ovarian Cancer Cell Line OVPA8

High-grade serous ovarian carcinoma (HGSOC) is the most frequent histological type of ovarian cancer and the one with worst prognosis. Unfortunately, the majority of established ovarian cancer cell lines which are used in the research have unclear histological origin and probably do not represent HGSOC. Thus, new and reliable models of HGSOC are needed. Ascitic fluid from a patient with recurrent HGSOC was used to establish a stable cancer cell line. Cells were characterized by cytogenetic karyotyping and short tandem repeat (STR) profiling. New generation sequencing was applied to test for hot-spot mutations in 50 cancer-associated genes and fluorescence in situ hybridization (FISH) analysis was used to check for TP53 status. Cells were analyzed for expression of several marker genes/proteins by reverse-transcription polymerase chain reaction (RT-PCR), fluorescence-activated cell sorting (FACS), and immunocytochemistry (ICC). Functional tests were performed to compare OVPA8 cells with five commercially available and frequently used ovarian cancer cell lines: SKOV3, A2780, OVCAR3, ES2, and OAW42. Our newly-established OVPA8 cell line shows morphologic and genetic features consistent with HGSOC, such as epithelial morphology, multiple chromosomal aberrations, TP53 mutation, BRCA1 mutation, and loss of one copy of BRCA2. The OVPA8 line has a stable STR profile. Cells are positive for EpCAM, CK19, and CD44; they have relatively low plating efficiency/ability to form spheroids, a low migration rate, and intermediate invasiveness in matrigel, as compared to other ovarian cancer lines. OVPA8 is sensitive to paclitaxel and resistant to cisplatin. We also tested two FGFR inhibitors; OVPA8 cells were resistant to AZD4547 (AstraZeneca, London, UK), but sensitive to the new inhibitor CPL304-110-01 (Celon Pharma, Łomianki/Kiełpin, Poland). We have established and characterized a novel cell line, OVPA8, which can be a valuable preclinical model for studies on high-grade serous ovarian cancer.

Origins based clinical and molecular complexities of epithelial ovarian cancer

Ovarian cancer is the most lethal of all common gynaecological malignancies in women worldwide. Ovarian cancer comprises of >15 distinct tumor types and subtypes characterized by histopathological features, environmental and genetic risk factors, precursor lesions and molecular events during oncogenesis. Recent studies on gene signature profiling of different subtypes of ovarian cancer have revealed significant genetic heterogeneity between and within each ovarian cancer histological subtype. Thus, an immense interest have shown towards a more personalized medicine for understanding the clinical and molecular complexities of four major types of epithelial ovarian cancer (serous, endometrioid, clear cell, and mucinous). As such, further in depth studies are needed for identification of molecular signalling network complexities associated with effective prognostication and targeted therapies to prevent or treat metastasis. Therefore, understanding the metastatic potential of primary ovarian cancer and therapeutic interventions against lethal ovarian cancer for the development of personalized therapies is very much indispensable. Consequently, in this review we have updated the key dysregulated genes of four major subtypes of epithelial carcinomas. We have also highlighted the recent advances and current challenges in unravelling the complexities of the origin of tumor as well as genetic heterogeneity of ovarian cancer.

HnRNP-L mediates bladder cancer progression by inhibiting apoptotic signaling and enhancing MAPK signaling pathways

Heterogeneous nuclear ribonucleoprotein L (hnRNP-L) is a promoter of various kinds of cancers, but its actions in bladder cancer (BC) are unclear. In this study, we investigated the function and the underlying mechanism of hnRNP-L in bladder carcinogenesis. Our results demonstrated that enhanced hnRNP-L expression in BC tissues was associated with poor overall survival of BC patients. Depletion of hnRNP-L significantly suppressed cell proliferation in vitro and inhibited xenograft tumor growth in vivo. Furthermore, downregulation of hnRNP-L resulted in G1-phase cell cycle arrest and enhanced apoptosis accompanied by inhibition of EMT and cell migration. All these cellular changes were reversed by ectopic expression of hnRNP-L. Deletion of hnRNP-L resulted in decreased expression of Bcl-2, enhanced expression of caspases-3, -6 and -9 and inhibition of the MAPK signaling pathway. These findings demonstrate that hnRNP-L contributes to poor prognosis and tumor progression of BC by inhibiting the intrinsic apoptotic signaling and enhancing MAPK signaling pathways.

Rational combination therapy with PARP and MEK inhibitors capitalizes on therapeutic liabilities in RAS mutant cancers

Mutant RAS has remained recalcitrant to targeted therapy efforts. We demonstrate that combined treatment with poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitors and mitogen-activated protein kinase (MAPK) kinase (MEK) inhibitors evokes unanticipated, synergistic cytotoxic effects in vitro and in vivo in multiple RAS mutant tumor models across tumor lineages where RAS mutations are prevalent. The effects of PARP and MEK inhibitor combinations are independent of BRCA1/2 and p53 mutation status, suggesting that the synergistic activity is likely to be generalizable. Synergistic activity of PARP and MEK inhibitor combinations in RAS mutant tumors is associated with (i) induction of BIM-mediated apoptosis, (ii) decrease in expression of components of the homologous recombination DNA repair pathway, (iii) decrease in homologous recombination DNA damage repair capacity, (iv) decrease in DNA damage checkpoint activity, (v) increase in PARP inhibitor-induced DNA damage, (vi) decrease in vascularity that could increase PARP inhibitor efficacy by inducing hypoxia, and (vii) elevated PARP1 protein, which increases trapping activity of PARP inhibitors. Mechanistically, enforced expression of FOXO3a, which is a target of the RAS/MAPK pathway, was sufficient to recapitulate the functional consequences of MEK inhibitors including synergy with PARP inhibitors. Thus, the ability of mutant RAS to suppress FOXO3a and its reversal by MEK inhibitors accounts, at least in part, for the synergy of PARP and MEK inhibitors in RAS mutant tumors. The rational combination of PARP and MEK inhibitors warrants clinical investigation in patients with RAS mutant tumors where there are few effective therapeutic options.

Combination of paclitaxel, bevacizumab and MEK162 in second line treatment in platinum-relapsing patient derived ovarian cancer xenografts

Advanced ovarian cancer is very responsive to first line platinum therapy, however almost invariably it relapses with a resistant disease. We have reported that patient derived ovarian xenografts (PDXs), independently from the degree of the initial response to cisplatin (DDP), show a significantly lower response to a second DDP cycle. We here report the effect of new combination regimens containing a MEK inhibitor (MEK), bevacizumab (BEV) and paclitaxel (PTX) as second line therapy in platinum-relapsing PDXs.

We selected three DDP-relapsing PDX models based on the presence of activation of the RAS/RAF/MEK/ERK axis, mutated p53, lack of PTEN expression and activation of the PI3K pathway. In all the selected xenograft models, the antitumor efficacy of the doublets can be summarized as PTX/BEV > BEV/MEK > PTX/MEK and the antitumor activity of the triple combination was higher than any double combination. All the different combinations were well tolerated. The present data corroborate the activity of bevacizumab in combination with chemotherapy for the treatment of relapsing ovarian tumors and suggest that the addition of another targeted agents (MEK inhibitor) can further increase the antitumor activity without any increase in toxicity. PDX models represent a useful model to test second line therapy after failure of DDP first line.

A patient-derived-xenograft platform to study BRCA-deficient ovarian cancers

Approximately 50% of high-grade serous ovarian cancers (HGSOCs) have defects in genes involved in homologous recombination (HR) (i.e., BRCA1/2). Preclinical models to optimize therapeutic strategies for HR-deficient (HRD) HGSOC are lacking. We developed a preclinical platform for HRD HGSOCs that includes primary tumor cultures, patient-derived xenografts (PDXs), and molecular imaging. Models were characterized by immunohistochemistry, targeted sequencing, and reverse-phase protein array analysis. We also tested PDX tumor response to PARP, CHK1, and ATR inhibitors. Fourteen orthotopic HGSOC PDX models with BRCA mutations (BRCA^MUT) were established with a 93% success rate. The orthotopic PDX model emulates the natural progression of HGSOC, including development of a primary ovarian tumor and metastasis to abdominal viscera. PDX response to standard chemotherapy correlated to that demonstrated in the patient. Pathogenic mutations and HGSOC markers were preserved after multiple mouse passages, indicating retention of underlying molecular mechanisms of carcinogenesis. A BRCA2^MUT PDX with high p-CHK1 demonstrated a similar delay of tumor growth in response to PARP, CHK1, and ATR inhibitors. A poly (ADP-ribose) polymerase (PARP) inhibitor radiotracer correlated with PARP1 activity and showed response to PARP inhibition in the BRCA2^MUT PDX model. In summary, the orthotopic HGSOC PDX represents a robust and reliable model to optimize therapeutic strategies for BRCA^MUT HGSOC.

Molecular Subtyping of Serous Ovarian Cancer Based on Multi-omics Data

Classification of ovarian cancer by morphologic features has a limited effect on serous ovarian cancer (SOC) treatment and prognosis. Here, we proposed a new system for SOC subtyping based on the molecular categories from the Cancer Genome Atlas project. We analyzed the DNA methylation, protein, microRNA, and gene expression of 1203 samples from 599 serous ovarian cancer patients. These samples were divided into nine subtypes based on RNA-seq data, and each subtype was found to be associated with the activation and/or suppression of the following four biological processes: immunoactivity, hormone metabolic, mesenchymal development and the MAPK signaling pathway. We also identified four DNA methylation, two protein expression, six microRNA sequencing and four pathway subtypes. By integrating the subtyping results across different omics platforms, we found that most RNA-seq subtypes overlapped with one or two subtypes from other omics data. Our study sheds light on the molecular mechanisms of SOC and provides a new perspective for the more accurate stratification of its subtypes.