Lactic dehydrogenase isozymes, 31P magnetic resonance spectroscopy, and in vitro antimitochondrial tumor toxicity with gossypol and rhodamine-123.

Three compounds that share specific antimitochondrial properties are gossypol, rhodamine-123, and lonidamine. We compare the antiproliferative activities of these drugs against six human cell lines derived from breast (T47-D), pancreas (MiaPaCa, RWP-2), prostate (DU-145), colon (HCT-8), and cervix (HeLa) carcinomas. Tumor cells enriched in cathodal LDH isozymes (LDH4 and LDH5) are significantly more sensitive to gossypol and rhodamine-123. When compared for ability to inhibit growth of human marrow in soft agar, 10 microM gossypol shows little effect on colony formation whereas 10 microM rhodamine-123 completely prevents stem cell growth, suggesting that gossypol may have the most favorable therapeutic index. Within 24 h of drug administration, there is a relative increase in intracellular inorganic phosphate pools and a marked decline in soluble high-energy phosphates in sensitive tumor cells, as measured by 31P magnetic resonance spectroscopy. These studies suggest that specific antimitochondrial agents might be selectively administered on the basis of tumor LDH isozyme content and noninvasively monitored for antiproliferative activity by 31P spectroscopy.