IT-62-B

IT-62-B, a new anthracycline isolated from fermentation broths of Streptomyces sp. IT-62, reversed certain tumor cell phenotypes in vitro including some of human origin. The observed normal phenotypes were anchorage dependence of cell growth, flattened cell morphology and restoration of actin stress fibers. The extent of the anchorage dependence of cell growth induced by IT-62-B was generally greater than that by doxorubicin or pirarubicin. The cell-flattening effect of IT-62-B on cells of T24 (human bladder), but not on C-33A (human cervix), accompanied inhibition of fos gene expression. T24 cells, once flattened by IT-62-B, retained their flat morphology even in drug-free, fresh medium and eventually died in several days. IT-62-B, unlike doxorubicin, only slightly inhibited the topoisomerase II reaction in vitro and DNA synthesis in isolated cell nuclei.

A new antibiotic, IT-62-B was isolated from the culture broth of Streptomyces sp. IT-62 by extraction with acetone and then with ethyl acetate, followed by conventional column chromatography using silica gel, Sephadex LH-20 and silica ODS. Its structure (C39H47NO15, MW 769) was determined by 1H, 13C NMR, MS, IR and UV spectrometric techniques to be a new member of the baumycin-group anthracyclines. It showed moderate activity against Gram-positive bacteria and had antitumor activity against various tumor cell lines. Further, antibiotic IT-62-B converted the morphology of ras-transformed NIH3T3 cells and T-cells back to normal at concentrations inhibiting cell growth by 30% or more.