melphalan and Hyperglycemia

We seek to exploit the natural tendency of melanomas and other tumors to convert glucose to lactate as a method for the selective intracellular acidification of cancer cells and for the potentiation of the activity of nitrogen-mustard antineoplastic agents. We performed this study to evaluate whether the induction of hyperglycemia (26 mM) could enhance the effects of lonidamine (LND, 100 mg/kg; intraperitoneally) on the induction of intracellular acidification, bioenergetic decline and potentiation of the activity of melphalan (LPAM) against DB-1 melanoma xenografts in mice. Intracellular pH (pHi ), extracellular pH (pHe ) and bioenergetics (β-nucleoside triphosphate to inorganic phosphate ratio, β-NTP/Pi) were reduced by 0.7 units (p < 0.001), 0.3 units (p > 0.05) and 51.4% (p < 0.05), respectively. The therapeutic response to LPAM (7.5 mg/kg; intravenously) + LND (100 mg/kg; intraperitoneally) was reduced by about a factor of three under hyperglycemic conditions relative to normoglycemia, producing a growth delay of 7.76 days (tumor doubling time, 5.31 days; cell kill, 64%) compared with LND alone of 1.70 days and LPAM alone of 0.29 days. Under normoglycemic conditions, LND plus LPAM produced a growth delay of 17.75 days, corresponding to a cell kill of 90% at the same dose for each of these agents. The decrease in tumor cell kill under hyperglycemic conditions correlates with an increase in tumor ATP levels resulting from increased glycolytic activity. However, hyperglycemia substantially increases lactic acid production in tumors by a factor of approximately six (p < 0.05), but hyperglycemia did not increase the effects of LND on acidification of the tumor, most probably because of the strong buffering action of carbon dioxide (the pKa of carbonic acid is 6.4). Therefore, this study demonstrates that the addition of glucose during treatment with LND diminishes the activity of this agent.

Topics: Acids; Animals; Cell Line, Tumor; Cell Proliferation; Energy Metabolism; Humans; Hydrogen-Ion Concentration; Hyperglycemia; Indazoles; Intracellular Space; Magnetic Resonance Spectroscopy; Male; Melanoma; Melphalan; Mice, Nude; Organ Specificity; Xenograft Model Antitumor Assays

Perfusate acidification with dilute hydrochloric acid augments tumor response rates in a rodent model of isolated limb perfusion (ILP). This study investigates the combination of metaiodobenzylguanidine (MIBG), a mitochondrial inhibitor, and systemic hyperglycemia as a strategy to selectively acidify tumors and thereby sensitize them to ILP.. Human melanoma xenografts were implanted into the hind limbs of athymic rats. When tumors reached 12 to 15 mm in diameter, animals were randomized to ILP with or without melphalan, with or without systemic MIBG, and hyperglycemia of 485 +/- 35 mg/dL. Intratumoral pH was measured during MIBG and glucose treatment by using magnetic resonance spectroscopy.. MIBG at 30 mg/kg plus hyperglycemia decreased intracellular pH by.6 units and extracellular pH by.8 units. MIBG at 22.5 mg/kg plus hyperglycemia decreased intracellular and extracellular pH by.4 and.5 units, respectively. Tumor growth was unaffected by systemic MIBG and hyperglycemia alone. When MIBG at 30 mg/kg and hyperglycemia were combined with ILP, tumor growth was delayed for 33 days after control ILP and for 44 days after melphalan ILP. However, this dose of MIBG was complicated by a 40% mortality rate after ILP. MIBG at 22.5 mg/kg, in combination with MIBG in the perfusate, did not cause mortality and delayed tumor growth by 51 days after melphalan ILP.. MIBG and hyperglycemia improve tumor response rates after ILP in a rodent model of human melanoma. Selective tumor acidification with MIBG and hyperglycemia may offer added benefit to current regional perfusion strategies.

Topics: 3-Iodobenzylguanidine; Animals; Antineoplastic Agents; Antineoplastic Agents, Alkylating; Chemotherapy, Cancer, Regional Perfusion; Disease Models, Animal; Drug Interactions; Female; Glucose; Humans; Hydrogen-Ion Concentration; Hyperglycemia; Intracellular Fluid; Melanoma; Melphalan; Random Allocation; Rats; Skin Neoplasms