Analysis of the viability of SiHa cells exposed to different fatty acids

The cells of a solid tumour are surrounded by a tumour microenvironment characterized by different gradients of hypoxia and acidosis. In the acidic and hypoxic areas, the cancer cells rewire their cellular metabolism to satisfy the demands for energy, growth and proliferation. This metabolic rewiring includes an increased dependency on fatty acids to support the tumour growth. In contrast, polyunsaturated fatty acids (PUFA) from the omega-3 family have been reported to have a protective impact against cancer. The cytotoxic effect of docosahexaenoic acid (DHA) alone and in the presence of 5 selected fatty acids has been previously observed on SiHa cells adapted to an acidic pH (6.5) in our research group. In turn, his master’s thesis has been motivated by the need to also investigate the cytotoxic effect of the counterpart of DHA in the omega-6 family, namely ω-6 docosapentaenoic acid (DPA). In order to compare the results with those previously collected on DHA cytotoxicity, this work aimed at (1) confirming the cytotoxicity of DHA at 100 µM on SiHa cells after 72h incubation, (2) determining if DPA is also toxic for these cancer cells, and (3) evaluating if the related cytotoxicity is maintained or inhibited in the presence of C16:0, C18:0, C18:1 n-9, C18:2 n-6, C18:3 n-3. All the experiments were performed with acidosis-adapted SiHa cells (pH 6.5) and parental cells (pH 7.4). We observed that the cytotoxic effects of DPA and DHA are quite similar. At pH 6.5 and for a concentration of 100 µM, the cell viability was around 20% for both fatty acids, while it remained much higher at pH 7.4. Similarly to what was observed for DHA, when DPA was combined with C16:0, C18:0 or C18:1, the cytotoxic effect on the acidosis-adapted SiHa cells was inhibited, whereas the related cytotoxicity was maintained for a combination with C18:2 or C18:3. Importantly, a kinetic study allowed to highlight that the cytotoxic effects of DHA and DPA are already visible after 24 hours of incubation. An additional objective of the present work was to investigate in which type of lipids do the fatty acids concentrate in the cells. The PUFA proportions were in general larger in the NL fraction than in the PL fraction at both pH. In contrast, the proportions of C16:0 were larger in the PL fraction than in the NL fraction, except in the condition where C16:0 was added alone at pH 6.5. Taken together, our results should contribute to a better knowledge on the potentiality of PUFAs in terms of prevention or therapeutic treatment against cancer diseases.