Molecular targeted therapy in ovarian cancer: what is on the horizon?

Melatonin Synergizes the Chemotherapeutic Effect of Cisplatin in Ovarian Cancer Cells Independently of MT1 Melatonin Receptors

BACKGROUND/AIM

Melatonin (MLT), through the interaction with membrane melatonin receptors MT1, can improve the effectiveness of cytostatic agents, including cisplatin (CP). The aim of this study was to examine the synergistic effect of MLT and CP in three cell lines: IOSE 364, SK-OV-3 and OVCAR-3, as well as to assess the role of MT1 receptors in this mechanism.

MATERIALS AND METHODS

Using the SRB assay we investigated the effect of different concentrations of CP and MLT on cell viability. Tests, using luzindole - MT1 inhibitor, allowed us to assess the potential involvement of MT1 in the mechanism of MLT action.

RESULTS

MLT at certain concentrations demonstrated a synergistic effect in combination with CP. The addition of luzindole did not affect the action of MLT in combination with CP.

CONCLUSION

In summary, the synergistic effect of MLT with CP seems to be independent of membrane MT1 receptors.

Co-expression and prognostic significance of the HER family members, EGFRvIII, c-MET, CD44 in patients with ovarian cancer

EGFR and HER-2 are important targets but none of the monoclonal antibodies or small molecule tyrosine kinase inhibitors specific for the HER members has been approved for the treatment of patients with ovarian cancers. In some studies, co-expression of other growth factor receptors has been associated with resistance to therapy with the HER inhibitors. The aim of the present study was to determine the relative expression, cellular location, and prognostic significance of HER-family members, the EGFR mutant (EGFRvIII) c-MET, IGF-1R and the cancer stem cell biomarker CD44 in 60 patients with FIGO stage III and IV ovarian cancer. At cut off >5% of tumour cells with positive staining, 62%, 59%, 65% and 45% of the cases were EGFR, HER-2, HER-3 and HER-4 positive, and 3%, 22% and 48.3% of the cases were positive for EGFRvIII, c-MET, and CD44 respectively. Interestingly, 23% co-expressed all four members of the HER family. On univariate analysis, only EGFR staining at >50% of tumour cells (HR = 3.57, p = 0.038) and CD44 staining at 3+ intensity (HR = 7.99, p = 0.004) were associated with a poorer overall survival. EGFR expression (HR = 2.83, p = 0.019) and its co-expression with HER-2, HER-3, HER-2/HER-3, and c-MET were all associated with poorer disease-free survival. Our results suggest co-expression of the HER-family members is common in Stage III and IV ovarian cancer patients. Further studies on the prognostic significance and predictive value of all HER family member proteins for the response to treatment with various forms of the HER inhibitors are warranted.

Kinetic modelling of in vitro data of PI3K, mTOR1, PTEN enzymes and on-target inhibitors Rapamycin, BEZ235, and LY294002

The phosphatidylinositide 3-kinases (PI3K) and mammalian target of rapamycin-1 (mTOR1) are two key targets for anti-cancer therapy. Predicting the response of the PI3K/AKT/mTOR1 signalling pathway to targeted therapy is made difficult because of network complexities. Systems biology models can help explore those complexities but the value of such models is dependent on accurate parameterisation. Motivated by a need to increase accuracy in kinetic parameter estimation, and therefore the predictive power of the model, we present a framework to integrate kinetic data from enzyme assays into a unified enzyme kinetic model. We present exemplar kinetic models of PI3K and mTOR1, calibrated on in vitro enzyme data and founded on Michaelis-Menten (MM) approximation. We describe the effects of an allosteric mTOR1 inhibitor (Rapamycin) and ATP-competitive inhibitors (BEZ235 and LY294002) that show dual inhibition of mTOR1 and PI3K. We also model the kinetics of phosphatase and tensin homolog (PTEN), which modulates sensitivity of the PI3K/AKT/mTOR1 pathway to these drugs. Model validation with independent data sets allows investigation of enzyme function and drug dose dependencies in a wide range of experimental conditions. Modelling of the mTOR1 kinetics showed that Rapamycin has an IC₅₀ independent of ATP concentration and that it is a selective inhibitor of mTOR1 substrates S6K1 and 4EBP1: it retains 40% of mTOR1 activity relative to 4EBP1 phosphorylation and inhibits completely S6K1 activity. For the dual ATP-competitive inhibitors of mTOR1 and PI3K, LY294002 and BEZ235, we derived the dependence of the IC₅₀ on ATP concentration that allows prediction of the IC₅₀ at different ATP concentrations in enzyme and cellular assays. Comparison of drug effectiveness in enzyme and cellular assays showed that some features of these drugs arise from signalling modulation beyond the on-target action and MM approximation and require a systems-level consideration of the whole PI3K/PTEN/AKT/mTOR1 network in order to understand mechanisms of drug sensitivity and resistance in different cancer cell lines. We suggest that using these models in a systems biology investigation of the PI3K/AKT/mTOR1 signalling in cancer cells can bridge the gap between direct drug target action and the therapeutic response to these drugs and their combinations.

Advantages of the avian model for human ovarian cancer

Ovarian cancer (OC) is the most lethal gynecological cancer. Early detection of OC is crucial for providing efficient treatment, whereas high mortality rates correlate with late detection of OC, when the tumor has already metastasized to other organs. The most prevalent type of OC is epithelial OC (EOC). Models that have been used to study EOC include the fruit fly, mouse and laying hen, in addition to human EOC cells in 3D culture in vitro. These models have helped in the elucidation of the genetic component of this disease and the development of drug therapies. However, the histological origin of EOC and early markers of the disease remain largely unknown. In this study, we aimed to review the relative value of each of the different models in EOC and their contributions to understanding this disease. It was concluded that the spontaneous occurrence of EOC in the adult hen, the prolific ovulation, the similarity of metastatic progression with that in humans and the advantages of using the chicken embryo for modelling the development of the reproductive system, renders the hen particularly suitable for studying the early development of EOC. Further investigation of this avian model may contribute to a better understanding of EOC, improve clinical insight and ultimately contribute to decreasing its mortality rates among humans.

Analyses of merlin/NF2 connection to FAK inhibitor responsiveness in serous ovarian cancer

OBJECTIVE

Focal adhesion kinase (FAK) is overexpressed in serous ovarian cancer. Loss of merlin, a product of the neurofibromatosis 2 tumor suppressor gene, is being evaluated as a biomarker for FAK inhibitor sensitivity in mesothelioma. Connections between merlin and FAK in ovarian cancer remain undefined.

METHODS

Nine human and two murine ovarian cancer cell lines were analyzed for growth in the presence of a small molecule FAK inhibitor (PF-271, also termed VS-6062) from 0.1 to 1 μM for 72 h. Merlin was evaluated by immunoblotting and immunostaining of a human ovarian tumor tissue array. Growth of cells was analyzed in an orthotopic tumor model and evaluated in vitro after stable shRNA-mediated merlin knockdown.

RESULTS

Greater than 50% inhibition of OVCAR8, HEY, and ID8-IP ovarian carcinoma cell growth occurred with 0.1 μM PF-271 in anchorage-independent (p<0.001) but not in adherent culture conditions. PF-271-mediated reduction in FAK Y397 phosphorylation occurred independently of growth inhibition. Suspended growth of OVCAR3, OVCAR10, IGROV1, IGROV1-IP, SKOV3, SKOV3-IP, A2780, and 5009-MOVCAR was not affected by 0.1 μM PF-271. Merlin expression did not correlate with serous ovarian tumor grade or stage. PF-271 (30 mg/kg, BID) did not inhibit 5009-MOVCAR tumor growth and merlin knockdown in SKOV3-IP and OVCAR10 cells did not alter suspended cell growth upon PF-271 addition.

CONCLUSIONS

Differential responsiveness to FAK inhibitor treatment was observed. Intrinsic low merlin protein level correlated with PF-271-mediated anchorage-independent growth inhibition, but reduction in merlin expression did not induce sensitivity to FAK inhibition. Merlin levels may be useful for patient stratification in FAK inhibitor trials.

Assessing the in vivo efficacy of doxorubicin loaded hyaluronan nanoparticles

Magnetic nanoparticles are attractive platforms for biomedical applications including diagnosis and treatment of diseases. We have shown previously that hyaluronan-coated superparamagnetic iron oxide nanoparticles (HA-SPIONs) enhanced the efficacy of the conjugated anticancer drug doxorubicin (DOX) in vitro against drug-sensitive and drug-resistant human ovarian cancer cells. In this manuscript, we report our findings on the efficacy of DOX loaded HA-SPIONs in vivo using subcutaneous and intraperitoneal SKOV-3 ovarian tumor models in nude mice. The accumulation of the nanoparticles in subcutaneous tumors following an intravenous nanoparticle administration was confirmed by magnetic resonance imaging, and its distribution in the tumors was evaluated by confocal microscopy and Prussian blue staining. DOX delivered by nanoparticles accumulated at much higher levels and distributed wider in the tumor tissue than intravenously injected free DOX, leading to significant reduction of tumor growth. The IVIS Spectrum for in vivo bioluminescence imaging was used to aid in therapy assessment of the DOX-loaded nanoparticles on intraperitoneal ovarian tumors formed by firefly luciferase expressing human ovarian SKOV-3 cells. DOX-loaded HA-SPIONs significantly reduced tumor growth, delayed tumor development, and extended the survival of mice. Thus, utilizing HA-SPIONs as drug delivery vehicles constitutes a promising approach to tackle CD44 expressing ovarian cancer.

Ovarian cancer molecular pathology

Ovarian cancer (OVC) is the fourth leading cause of cancer mortality among women in Europe and the United States. Its early detection is difficult due to the lack of specificity of clinical symptoms. Unfortunately, late diagnosis is a major contributor to the poor survival rates for OVC, which can be attributed to the lack of specific sets of markers. Aside from patients sharing a strong family history of ovarian and breast cancer, including the BRCA1 and BRCA2 tumor suppressor genes mutations, the most used biomarker is the Cancer-antigen 125 (CA-125). CA-125 has a sensitivity of 80 % and a specificity of 97 % in epithelial cancer (stage III or IV). However, its sensitivity is 30 % in stage I cancer, as its increase is linked to several physiological phenomena and benign situations. CA-125 is particularly useful for at-risk population diagnosis and to assess response to treatment. It is clear that alone, CA-125 is inadequate as a biomarker for OVC diagnosis. There is an unmet need to identify additional biomarkers. Novel and more sensitive proteomic strategies such as MALDI mass spectrometry imaging studies are well suited to identify better markers for both diagnosis and prognosis. In the present review, we will focus on such proteomic strategies in regards to OVC signaling pathways, OVC development and escape from the immune response.

The role of secondary cytoreductive surgery in patients with recurrent epithelial ovarian, tubal, and peritoneal cancers: a comparative effectiveness analysis

Background. All published reports concerning secondary cytoreductive surgery for relapsed ovarian cancer have essentially been observational studies. However, the validity of observational studies is usually threatened from confounding by indication. We sought to address this issue by using comparative effectiveness methods to adjust for confounding. Methods. Using a prospectively collected administrative health care database in a single institution, we identified 1,124 patients diagnosed with recurrent epithelial, tubal, and peritoneal cancers between 1990 and 2009. Effectiveness of secondary cytoreductive surgery using the conventional Cox proportional hazard model, propensity score, and instrumental variable were compared. Sensitivity analyses for residual confounding were explored using an array approach. Results. Secondary cytoreductive surgery prolonged overall survival with a hazard ratio (95% confidence interval) of 0.76 (range 0.66-0.87), using the Cox proportional hazard model. Propensity score methods produced comparable results: 0.75 (range 0.64-0.86) by nearest matching, 0.73 (0.65-0.82) by quintile stratification, 0.71 (0.65-0.77) by weighting, and 0.72 (0.63-0.83) by covariate adjustment. The instrumental variable method also produced a comparable estimate: 0.75 (range 0.65-0.86). Sensitivity analyses revealed that the true treatment effects may approach the null hypothesis if the association between unmeasured confounders and disease outcome is high. Conclusions. This comparative effectiveness study provides supportive evidence for previous reports that secondary cytoreductive surgery may increase overall survival for patients with recurrent epithelial, tubal, and peritoneal cancers.

Biologic therapies and personalized medicine in gynecologic malignancies

Through advances in human genomic sequencing, the unique molecular biology that predisposes certain individuals to either health or disease has now been illuminated. Although many malignancies behave similarly on a phenotypic level, biologically there exist multiple layers of interconnected molecular and cellular pathways that may make each patient’s disease significantly more unique than previously appreciated. In gynecologic oncology, the most progress in developing targeted biologics has been in the treatment of ovarian cancers. Future investigations will see further development in endometrial and cervical cancers. Technology such as whole genome sequencing can theoretically identify the individual tumor’s genetic profile; however, identifying the priority pathways for therapeutic interventions and subsequent complex interactions remains a significant challenge. New therapeutic technologies such as siRNA and immune modulators will also play a promising role in the movement toward individualized therapies. It is hoped that the identification and use of targeted agents will lead to individualized care that in turn will lead to significantly improved outcomes manifested by more cures and better quality of life through amelioration of toxicities.