Ghosal, N.; Biswas, D.; Chaudhuri, D.; Sarkar, M.; Giri, K.; PAL, R.

Background: The ability of TRAIL to specifically induce apoptosis in cancer cells makes it a promising candidate to be an effective chemotherapeutic drug. But resistance to TRAIL treatment is a major obstacle. Finding combinatorial therapies that make resistant tumors more susceptible to TRAIL is an effective preclinical approach. In this work, we investigated the possibility that pre-treatment of paclitaxel may promote apoptosis in TRAIL-resistant breast cancer cells. Methods: In silico analysis was done to investigate the binding affinity between TRAIL receptors (DR5 and DCR2) and paclitaxel via docking and MD simulation. To check whether any non-lethal dose of paclitaxel can modulate the expression of TRAIL receptors, qPCR was done in paclitaxel treated breast cancer cells. Next, paclitaxel was pre-administered to TRAIL-resistant MCF7 and MDA-MB-453 human breast cancer cells followed by rhTRAIL treatment. Cell viability and survival was evaluated using the MTT assay and colony formation assay, respectively. Immunoblot for caspase-3 was performed to study apoptosis. The expression level changes of DR5 and DCR2 were analyzed post-treatment using qPCR and immunoblot assay. Results: In silico analysis showed that paclitaxel can bind with higher stability to DCR2 in comparison to DR5 thereby changing the preference of TRAIL molecules towards DR5. Next, in cell line experiments we observed that administering a non-lethal dose of paclitaxel to MDA-MB-231 and MCF7 breast cancer cells resulted in no significant cell death but led to an increase in DR5 and a decrease in DCR2 expression at both the transcript and protein levels. Furthermore, in TRAIL-resistant MCF7 and MDA-MB-453 cells, pre-treatment with paclitaxel followed by rhTRAIL administration induced significant cell death due to paclitaxel induced increase in DR5 as well as decrease in DCR2 expression at both the transcript and protein levels. Moreover, long term survival of MDA-MB-453 cells was significantly lower when pretreated with paclitaxel and exposed to rhTRAIL compared to control, paclitaxel alone or rhTRAIL alone group. Conclusion: Thus, our study uncovers a novel therapeutic strategy to overcome TRAIL resistance underscoring the clinical potential of using a non-lethal dose of paclitaxel to modulate TRAIL receptor dynamics. Future research should be aimed at exploring the potentiality of using paclitaxel-based combinatorial approaches in crafting effective TRAIL therapies.