Targeted Therapy in Ovarian Cancer Treatments

Author: Brianna Nee

Editor: Liane Xu and Meagn Liu

Artist: Serena Yung

According to the Mayo Clinic, “[Ovarian cancer is] a type of cancer that begins in the ovaries”. Survival and the success of treatment for those who suffer from this cancer depend on the stage of cancer at the time of diagnosis. Ovarian cancer is usually detected at later stages when cancer has spread beyond the primary site. At a later stage, cancer has a poor prognosis and the treatment outcome, when compared to cancer detected at earlier stages, is worse. Currently, only 49.1% of patients diagnosed with ovarian cancer live 5 or more years after diagnosis. With this in mind, treatment for ovarian cancer is of importance in improving the prognosis for ovarian cancer patients.

Chemotherapy is a well-known treatment for cancer, but emerging targeted therapies can also be effective treatments. Chemotherapy drugs target cells that grow rapidly and would damage cancer cells but it would also damage normal cells like hair follicles. According to the National Cancer Institute, “[Targeted therapies] act on specific molecular targets that are associated with cancer”, which means that they are more likely to target only cancer cells and not all rapidly growing cells in the body. This allows for a reduction, but not elimination, of side effects for patients. In addition, targeted therapies may be used alongside standard chemotherapy drugs to treat cancer.

For ovarian cancer, poly- adenosine diphosphate-ribose polymerase (PARP) inhibitors may be an option for patients with homologous recombination deficiency (HRD) because of a concept called synthetic lethality. Synthetic lethality involves inhibiting two pathways to ensure cell death because inhibiting one pathway is non-lethal. PARP inhibitors inhibit ​​the PARP enzyme which causes single-stranded breaks and eventually double-stranded breaks in DNA. To repair these double-stranded breaks, cells typically use homologous recombination repair (HRR), an error-free pathway. However, if there is an HRD, then the cells will either not repair the double-stranded breaks or there will be errors in the repair which would lead to cell death. The breast cancer genes, known as BRCA, play a pivotal role in the HRR pathway, so cancers with BRCA mutations will have HRD. Ovarian cancer patients may be tested for the BRCA mutation to determine whether they are a good candidate for PARP inhibitor treatment. PARP inhibitors target both the pathway used by PARP and the homologous recombination repair pathway to induce cell death in cancers where DNA repair is already weakened.

PARP inhibitors, among other types of targeted therapy, offer treatment specific to patients with certain types of ovarian cancers. More research conducted regarding the genetics and molecular mechanisms surrounding ovarian cancer may produce new therapies for ovarian cancer patients or allow us to repurpose existing drugs.

 

Citation:

“Cancer of the Ovary - Cancer Stat Facts.” SEER, seer.cancer.gov/statfacts/html/ovary.html.

Drew, Yvette. “The Development of PARP Inhibitors in Ovarian Cancer: from Bench to Bedside.” British Journal of Cancer, Nature Publishing Group, 15 Dec. 2015,

www.ncbi.nlm.nih.gov/pmc/articles/PMC4816267/#bib59.

“Ovarian Cancer.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 25 July 2019,

www.mayoclinic.org/diseases-conditions/ovarian-cancer/symptoms-causes/syc-20375941.

“Targeted Cancer Therapies Fact Sheet.” National Cancer Institute,

www.cancer.gov/about-cancer/treatment/types/targeted-therapies/targeted-therapies-fact-sheet.

“Targeted Therapy for Ovarian Cancer.” American Cancer Society,

www.cancer.org/cancer/ovarian-cancer/treating/targeted-therapy.html.

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