Nakayasu M, Shima H, Aonuma S, Nakagama H, Nagao M, Sugimura T
Carcinogenesis Division, National Cancer Center Research Institute, Tokyo, Japan.
Proc Natl Acad Sci U S A. 1988 Dec;85(23):9066-70. doi: 10.1073/pnas.85.23.9066.
a1-1 cells, a transformant line obtained by transfection of NIH 3T3 cells with human c-Ha-rasT24 (hc-Ha-rasT24), were converted to morphologically normal flat cells following a 2-week culture in the presence of benzamide (BA), an inhibitor of poly(ADP-ribose) polymerase [ADP-ribosyltransferase (polymerizing); EC 2.4.2.30]. Concomitant with these morphological changes was the loss of the exogenous hc-Ha-rasT24 sequence. When cells were cultured without transfer, multiple clusters of flat revertant cells surrounded by transformed cells within single colonies of a1-1 cells were observed. This, together with the slow growth rate of flat cells in the presence of BA, indicated that flat revertants were induced rather than selected by BA. Flat cells isolated from mixed colonies completely lost the exogenous and amplified hc-Ha-rasT24 gene. In contrast, the endogenous mouse c-Ha-ras in flat revertant cells was not lost during culture with BA. Similarly, the endogenous hc-Ha-rasT24 in human bladder carcinoma T24 cells was not affected by BA. By using various chemicals, it was suggested that inhibition of poly(ADP-ribose) polymerase induces an efficient and specific loss of the exogenous transforming genes including Ki-ras, N-ras, c-raf, and ret-II.
a1-1细胞是通过用人c-Ha-rasT24（hc-Ha-rasT24）转染NIH 3T3细胞获得的转化细胞系，在聚（ADP-核糖）聚合酶[ADP-核糖基转移酶（聚合）；EC 2.4.2.30]的抑制剂苯甲酰胺（BA）存在下培养2周后，其形态转变为形态正常的扁平细胞。与这些形态变化同时发生的是外源hc-Ha-rasT24序列的丢失。当细胞不进行传代培养时，在a1-1细胞的单个集落中观察到多个由转化细胞包围的扁平回复细胞簇。这一点，连同扁平细胞在BA存在下生长缓慢的速率，表明扁平回复细胞是由BA诱导而非选择产生的。从混合集落中分离出的扁平细胞完全丢失了外源的和扩增的hc-Ha-rasT24基因。相反，扁平回复细胞中的内源性小鼠c-Ha-ras在与BA共同培养期间并未丢失。同样，人膀胱癌T24细胞中的内源性hc-Ha-rasT24不受BA的影响。通过使用各种化学物质，提示聚（ADP-核糖）聚合酶的抑制诱导包括Ki-ras、N-ras、c-raf和ret-II在内的外源转化基因有效且特异性地丢失。
