Ovarian cancer: designing effective vaccines and specific diagnostic tools

Oligopeptides for Immunotherapy Approaches in Ovarian Cancer Treatment

BACKGROUND

Anti-ovarian cancer vaccines based on minimal immune determinants uniquely expressed in ovarian cancer biomarkers appear to promise a high level of sensitivity and specificity for ovarian cancer immunodiagnostics, immunoprevention, and immunotherapy.

METHODS

Using the Pir Peptide Match program, three ovarian cancer biomarkers - namely, sperm surface protein Sp17, WAP four-disulfide core domain protein 2, and müllerian-inhibiting substance - were searched for unique peptide segments not shared with other human proteins. Then, the unique peptide segments were assembled to define oligopeptides potentially usable as synthetic ovarian cancer antigens.

RESULTS AND CONCLUSION

This study describes a methodology for constructing ovarian cancer biomarkerderived oligopeptide constructs that might induce powerful, specific, and non-crossreactive immune responses against ovarian cancer.

TSPAN12 Precedes Tumor Proliferation by Cell Cycle Control in Ovarian Cancer

TSPAN12, a member of the tetraspanin family, has been highly connected with the pathogenesis of cancer. Its biological function, however, especially in ovarian cancer (OC), has not been well elucidated. In this study, The Cancer Genome Atlas (TCGA) dataset analysis revealed that upregulation of TSPAN12 gene expression was significantly correlated with patient survival, suggesting that TSPAN12 might be a potential prognostic marker for OC. Further exploration showed that TSPAN12 overexpression accelerated proliferation and colony formation of OVCAR3 and SKOV3 OC cells. Knockdown of TSPAN12 expression in A2780 and SKOV3 cells decreased both proliferation and colony formation. Western blot analysis showed that several cyclins and cyclin-dependent kinases (CDK) (e.g., Cyclin A2, Cyclin D1, Cyclin E2, CDK2, and CDK4) were significantly involved in the regulation of cell cycle downstream of TSPAN12. Moreover, TSPAN12 accelerated mitotic progression by controlling cell cycle. Thus, our data demonstrated that TSPAN12 could be a novel molecular target for the treatment of OC.

A robust immune system conditions the response to abagovomab (anti-idiotypic monoclonal antibody mimicking the CA125 protein) vaccination in ovarian cancer patients

INTRODUCTION

Despite encouraging phase I and II study results, vaccination of ovarian cancer patients with abagovomab - an anti-idiotypic mAb that mimics the ovarian cancer CA125 protein - failed to demonstrate efficacy in the phase III trial named MIMOSA (NCT00418574). We postulated that in this trial patients with a more robust immune system did respond to abagovomab but went undetected among a larger number of non-responders. We also postulated that assessment of the immune system status ahead of abagovomab administration might predict patients' propensity to respond to abagovomab.

MATERIALS AND METHODS

The immune system status was assessed as percentage and absolute count of CD8⁺ T cells producing IFN-γ after stimulation with Staphylococcal Enterotoxin B (SEB) in 80 patients on abagovomab and 31 patients on placebo from the MIMOSA trial ahead of treatment. Optimal cutoffs of the two variables were calculated by the web application "Cutoff Finder" as the points with most significant (log-rank test) splits based on relapse-free survival (RFS). The Kaplan-Meier curves and log-rank test served to estimate and compare RFS in patients with percentage and absolute count of IFN-γ producing CD8⁺ T cells around the cutoffs.

RESULTS

Patients on abagovomab with IFN-γ producing CD8⁺T cell percentage above the cutoff had a better RFS (p=0.042) than those with IFN-γ producing CD8⁺T cell percentage below the cutoff. Patients on abagovomab with IFN-γ producing CD8⁺T cell absolute count above the cutoff had a better RFS (p=0.019) than those with IFN-γ producing CD8⁺T cell absolute counts below the cutoff. Consistently, the RFS of patients on abagovomab with IFN-γ producing CD8⁺T cell percentage and absolute counts values below the respective cutoffs was identical to that of patients on placebo. Neither the percentage nor the absolute count of IFN-γ producing CD8⁺T cells correlated with RFS in patients on placebo.

CONCLUSIONS

A robust immune system is essential to obtain a clinical response in OC patients undergoing abagovomab immunotherapy whereas a robust immune system does not confer per se a survival advantage. Further work will clarify whether the results shown here apply only in the present setting or extend to other types of cancer and/or immunotherapeutic agents.