Tumor microenvironment determines drug efficacy in vitro - apoptotic and anti-inflammatory effects of 15-lipoxygenase metabolite, 13-HpOTrE.

Recent studies using 3D scaffolds have emphasized the importance of the surrounding stroma on chemoresistance in drug efficacy screenings. Since 15-lipoxygenase (15-LOX) metabolites reduced growth of breast, colon, prostate, lung and leukemia cancer cells in 2D cell culture, we were intrigued by the direct comparison of 15-LOX metabolite efficacy in 2D and 3D culture including a stroma equivalent. Herein, we studied the effects of 15-LOX metabolites 13-HpOTrE, 13-HpODE, and 15-HpETE on cutaneous squamous cell carcinoma cells. All metabolites reduced the viability of cancer cells in 2D culture below 10% at 100 µM of each substance. 13-HpOTrE, being the most active agent with respect to cytotoxicity and apoptosis was selected for further experiments. Other than with the 2D culture, we did not obverse cell death, neither from lactate dehydrogenase release, nor from morphology when applying 13-HpOTrE onto the surface of the 3D tumor constructs for one week. Next, we investigated the protein expression of peroxisome proliferator activated receptor gamma, for which the ligand is 13-HpOTrE, and Bcl-2 protein, an apoptosis regulator, but did not find any change following 13-HpOTrE administration. However, 13-HpOTrE treatment reduced the release of interleukin-6, bringing it closer to the level of tumor-free constructs. In conclusion, 13-HpOTrE reduces viability of skin cancer cells in 2D cultures only but modulates inflammatory cytokine levels in the corresponding 3D tumor constructs, too. These studies highlight the need for screening of anticancer drugs employing 3D tumors and including tumor microenvironment in the screening process to increase the low success rate of clinical trials in oncology.