Effects transformed zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA C A NC ER LETTERS Cancer Letters 74 (1993) 197-202 of signalling transduction modulators on the phenotypes in v-H-ras-transformed NIH 3T3 cells Min-Liang Kuo *, Jaw-Jou Kang, Nae-Cherng Yang zyxwvutsrqponmlkjihgfedcbaZYXWV Institutes of Toxicology, College of Medicine, National Taiwan University. No. I, Section 1, Jen-Ai Road, Taipei. Taiwan Republic of China (Received 17 August 1993; revision received 2 September 1993; accepted 9 September 1993) zyxwvutsrqponmlkjihgfedc Abstract Several signalling transduction modulators were used to examine their effects on the morhpological changes, foci formation in soft agar and cellular growth in v-H-ras-transformed NIH 3T3 cells. The results from this study showed that specific tyrosine kinase inhibitors (genistein and tyrphostin 23) and cyclic AMP-elevating agents (forskolin and 3-isobutyl-1-methyl-xanthine) could effectively induce differential flat phenotype of v-H-ras transformant at micromolar concentrations. At the same dose range, both signalling modulators also caused a significant suppression of anchorage-independent and cellular growth in the same transformant. By contrast, compound inhibitors such as protein kinase C (staurosporin and H-7), phospholipase A, (aristolochic acid), phospholipase C (neomycin sulfate) and cyclooxygenase (indomathacin) all did not alter the cellular morphology or foci formation in soft agar, although PKC inhibitors exhibited a slight inhibition on the cellular growth. Based on these observations, we propose that the alterations of protein kinase A or tyrosine kinase-associated signal pathways is necessary and the original cause of the transformation event, but that increase of the activities of protein kinase C, phospholipase C. phospholipase A, or cyclooxygenase probably is an indirect result of the v-H-ras-mediated transformation. Key words: v-H-ras-transformed NIH 3T3 cells; Genistein; Tyrphostin-23; Forskolin: 3-isobutyl-1-methyl-xanthine, IBMX; Staurosporin; HT; Neomycin sulfate; Aristolochic acid zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIH 1. Introduction The three zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA ras oncogenes, H-, N-, and K-ras en- code highly related 21 kDa proteins which are ubi- quitously expressed and thought to be involved in the control of proliferation [l]. Activated ras on- * Corresponding author. Abbreviations: H-7. I-(5isoquinolinylsuIfonyl)-2-methylpiper- asine; IBMX, 3-isobutyl-I-methyl-xanthine; PKC, protein kinase C; PLC, phospholipase C; PLA,, phospholipase A,. cogenes have been detected in a wide range of human tumors [2], and overexpression of normal ras proto-oncogenes or activation of ras on- cogenes by point mutations induces tumorigenic transformation in a number of cell lines [l]. Although numerous alterations of cellular activi- ties are associated with transformation by ras- encoded p21 proteins, the nature of the critical cellular effector proteins (targets) that interact with p2 1ras and whose participation is necessary for transformation is still not clear. 0304-3835/93/$06.00 SSDI 0304-3835(93)03 18 l-4