Influence of docosahexaenoic acid in vitro on intracellular adriamycin concentration in lymphocytes and human adriamycin-sensitive and -resistant small-cell lung cancer cell lines, and on cytotoxicity in the tumor cell lines.

An increase in the therapeutic effects of cancer chemotherapeutic agents and circumvention of drug resistance in cancer cells might result from an increase in the intracellular drug level. Alteration of the lipid domain of the cell membrane can result in a higher intracellular drug level. This alteration was achieved in human lymphocytes and in human adriamycin (ADR)-sensitive and -resistant small-cell lung carcinoma cells in vitro by incubation with docosahexaenoic acid (22:6). Incorporation of the fatty acid in cellular phospholipids was measured by gas chromatographic analysis. A significant increase of 22:6 could be reached without loss of viability in all 3 cell types. Incorporation was demonstrated notably in the phosphatidyl choline, phosphatidyl ethanolamine and phosphatidylserine, and was most pronounced in the phosphatidyl choline of the ADR-resistant line. After a 1-hr incubation with ADR, a 10-30% increase in intracellular adriamycin concentration was found in all 3 cell types previously incubated for 4 days with 22:6. After 1 hr incubation with ADR there was no increase in cytotoxicity in the sensitive cell line when measured by soft agar clonogenic assay and a partial reversal (52 to 14) of resistance factor (ratio of drug doses to produce 50% growth inhibition) in the resistant cell line. Increasing the time of ADR exposure from 1 to 4 hr further reduced the resistance factor to 8.6.