Introduction:

Ovarian cancer (OvCa) has a poor prognosis with a 5-year survival rate of ~50%. Treatment includes surgery and chemotherapy consisting of carboplatin (CP) and paclitaxel. Despite initial responses, resistance frequently develops, leading to recurrence. A high-throughput screen (HTS) by our lab identified 308 compounds that could resensitize OvCa cells to CP. The present study aimed to validate several lead compounds that targeted the adrenoceptor ADRA2A.

Research Question or Hypothesis:

Activation of ADRA2A enhances the chemotoxicity of carboplatin in OvCa tumor cells.

Study Design:

Quantitative measurement of cell viability by MTT absorbance or number of colonies formed in response to drug treatments was performed. Cells were treated with CP ± ADRA2A compounds and compared to control (no treatment), CP-only control, or combination CP+ADRA2A drug.

Methods:

The HTS screen used a compound library to identify drugs that may alter CP-induced cytotoxicity. In HTS, the cells were treated with the IC50 dose of CP (400µM) and each compound (50µM) for 48h. Viability was measured by MTT absorbance. CP dose curves (1-2000µM) were tested alone and in combination with ADRA2A agonists xylazine, dexmedetomidine, and clonidine (50 or 100µM) to assess their effects on CP IC50 values. Colony formation was evaluated using the IC50 of CP (1µM) ± 25µM ADRA2A compound. Cytotoxicity was also measured using cells with ectopic ADRA2A overexpression.

Data Analysis:

GraphPad Prism 10 was used for statistical analysis by One-Way ANOVA or Student's t-test (p<0.05), and IC50 values were calculated by dose-response nonlinear regression.

Results:

Pharmacologic activation or genetic upregulation of ADRA2A significantly enhanced CP cytotoxicity, as indicated by reduced CP IC50 values and fewer colonies formed compared to CP alone.

Conclusion:

Activating ADRA2A may increase OvCa tumor cell sensitivity to CP, offering a novel mechanism to enhance CP treatment efficacy. Further in vivo evaluation of ADRA2A is warranted.