Role of the ATP7A Transporter in Ovarian Cancer

Overview

Ovarian cancer has the highest mortality rate among all gynecologic cancers, with most patients presenting with advanced stage tumors. About a third of patients do not respond to primary platinum-based chemotherapy treatment, and over time up to 80 % of others develop chemoresistance, rendering recurrent disease incurable. Despite all the studies published in the literature, it has not been proven that the number of cells with expressed ATP7A in certain tumors increases independently of the therapy. In addition, no study has been conducted on a sample of patients with confirmed serous histology of ovarian cancer only. The aim of the study is to demonstrate increased expression of the ATP7A transporter in cells resistant to carboplatin.

RATIONALE: Recent studies suggest that the copper efflux transporters ATP7A plays an important role in platinum resistance. Despite all the studies published in the literature, it has not been proven that the number of cells with expressed ATP7A in certain tumors increases independently of the therapy. In addition, no study has been conducted on a sample of patients with confirmed serous histology of ovarian cancer only. The literature concludes that new methods are required to detect resistant tumor cells at an early chemotherapy stage and suitably adapt treatment. There is still much uncertainty regarding how the fate of platinum compounds in a cell follows the regulatory copper pathways, especially during transport from the cell. The question is also to what extent these processes are cell-specific, especially because experiments to date regarding the role of ATP7A in resistance to platinum compounds have been conducted on nonserous cell lines (especially of the endometrioid histological type). AIM OF THE STUDY: Study will evaluate the ATP7A transporter as an important mediator of chemoresistance to platinum compounds to obtain an additional criterion for the optimal treatment strategy for serous ovarian cancer patients. The focus will primarily be on intrinsic chemoresistance, which determines the initial response to chemotherapy. Research to date has failed to evaluate the influence of ATP7A transporter expression solely on serous ovarian cancer. The study will demonstrate increased expression of the ATP7A transporter in cells resistant to carboplatin. Because the measurement of ATP7A in bodily fluids is unreliable, the plan is to measure ceruloplasmin in the patients' ascites. Ceruloplasmin is the main copper-transporting protein in the blood. It is synthesized in the cell and, according to findings in the literature, it is ATP7A that is responsible for delivering copper to ceruloplasmin. When copper binds to ceruloplasmin, there is no other way for it to cross the plasma membrane than via the ATP7A transporter. By measuring the ceruloplasmin level in the ascites, ATP7A activity or its localization on the plasma membrane could indirectly be measured as well. To confirm the suitable measurement of ceruloplasmin in the ascites, its values in the patients' blood plasma and tissue will be measured. METHODS:prospective clinical trial It will include 30 high-grade serous ovarian cancer patients (FIGO stages III and IV) with ascites. The patients will be presented to the gynecological-oncological consultation team at the Ljubljana Division of Gynecology and Obstetrics. Patients for whom neoadjuvant chemotherapy is recommended will be included in the trial. STATISTICAL ANALYSES: The normality of numerical variables' distribution will be tested with the Shapiro-Wilk test. Relevant parametric tests (Student's t-test) or nonparametric tests (the two-tailed Mann-Whitney U-test) will be used to compare groups.