CPZ-Analogs Induce Mitochondrial Dysfunction, Apoptosis and S-Phase Accumulation in OSCC

Objectives: Oral squamous cell carcinoma (OSCC) is the 8^th most common cancer in the United States with a five-year survival rate of approximately 40% for patients with advanced disease. Our previous studies revealed that Capsazepine (CPZ), a TRPV1 antagonist, has significant anti-tumor effects in OSCC via a novel mechanism-of-action that is independent of TRPV1 interactions. We aimed to develop novel analogs, based upon the CPZ pharmacophore, with more potent anti-tumor effects than CPZ in vivo. Objectives: To determine the efficacy and the mechanism(s)-of-action of novel CPZ analogs.
Methods: Mice were inoculated with 3 X 10⁶ Cal27 cells. Once tumors reached 100 mm³, mice were then treated every other day with CIDD24, CIDD99, CIDD111, or CPZ (40μg) via intra-tumor injection for two weeks. Cell cycle analysis and mitochondrial depolarization assays were used to determine if the CPZ analogs affect the cell cycle distribution and mitochondrial function.
Results: CIDD99 had significant anti-tumor effects in vivo (p<0.001). While CIDD24 was equally potent to the parent compound CPZ, CIDD111 merely displayed a trend in reducing tumor growth but not significantly. Our previous TRPV1 knockdown studies confirmed CPZ induces apoptosis in a TRPV1 independent manner. However unlike CPZ, calcium imaging studies confirmed that CIDD24 activates TRPV1. Thus the role of TRPV1 cannot be ruled out as a potential mechanism-of-action for CIDD24. This study demonstrates an S phase accumulation and a dose-dependent mitochondrial depolarization with subsequent apoptosis in response to the CPZ analogs.
Conclusions: CPZ analogs are more efficacious in treating OSCC due to their enhanced ability to cause mitochondrial depolarization and apoptosis. Calcium imaging studies of all analogs are underway in addition to studies evaluating the anti-proliferative effects in the absence of TRPV1 in order to determine if mitochondrial depolarization is related to TRPV1 activation.