Hamel E, Katoh F, Mueller G, Birchmeier W, Yamasaki H
International Agency for Research on Cancer, Lyon, France.
Cancer Res. 1988 May 15;48(10):2832-6.
We have tested transforming growth factor beta (TGF beta) in the two-stage BALB/c 3T3 cell transformation assay for possible tumor-promoting activity, since it has several effects similar to those of tumor-promoting phorbol esters. After initiation of BALB/c 3T3 cells with 3-methylchol-anthrene, treatment with TGF beta at 1 ng/ml alone or in combination with epidermal growth factor (EGF) for 4 weeks enhanced the number of transformed foci by 5- to 6-fold in comparison with uninitiated cells. Initiation treatment alone induced no or very few transformed foci in several assays. Treatment with phorbol-12,13-didecanoate (PDD) at 100 ng/ml for 4 weeks enhanced the number of transformed foci in initiated BALB/c 3T3 cells by 4- to 5-fold in comparison with uninitiated cells. Thus, TGF beta at 1 ng/ml is as potent as PDD at 100 ng/ml for tumor-promoting activity in the two-stage BALB/c 3T3 cell transformation assay. The enhancing effect of TGF beta was dose-related in the dose range tested (0.03-1 ng/ml) and was not reversible. Some of the foci induced by combined MCA-TGF beta-EGF treatment were cloned, and eight out of nine clones tested produced tumors in nude mice. TGF beta (1 ng/ml) plus EGF (2 ng/ml) increased the saturation density to a similar extent as PDD (100 ng/ml) but did not affect the growth of BALB/c 3T3 cells. We observed no change in junctional intercellular communication, as measured by the dye transfer method, when cells were treated with TGF beta during the two-stage BALB/c 3T3 cell transformation assay. Nevertheless, there was selective communication between transformed and surrounding nontransformed cells; MCA-TGF beta transformed cells intercommunicated among themselves but not with surrounding nontransformed cells. Our results indicate that TGF beta has potent tumor-promoting activity in vitro, but that this activity is not mediated by a complete blockage of intercellular communication, as is suggested for phorbol ester tumor promoters.
我们已经在两阶段BALB/c 3T3细胞转化试验中检测了转化生长因子β（TGFβ）是否具有潜在的促肿瘤活性，因为它具有一些与促肿瘤佛波酯类似的作用。用3-甲基胆蒽启动BALB/c 3T3细胞后，单独用1 ng/ml的TGFβ或与表皮生长因子（EGF）联合处理4周，与未启动的细胞相比，转化灶的数量增加了5至6倍。在几次试验中，单独的启动处理未诱导出或仅诱导出极少的转化灶。用100 ng/ml的佛波-12,13-二癸酸酯（PDD）处理4周，与未启动的细胞相比，启动后的BALB/c 3T3细胞中转化灶的数量增加了4至5倍。因此，在两阶段BALB/c 3T3细胞转化试验中，1 ng/ml的TGFβ在促肿瘤活性方面与100 ng/ml的PDD一样有效。在所测试的剂量范围内（0.03 - 1 ng/ml），TGFβ的增强作用与剂量相关且不可逆。对MCA-TGFβ-EGF联合处理诱导的一些灶进行了克隆，所测试的9个克隆中有8个在裸鼠中产生了肿瘤。TGFβ（1 ng/ml）加EGF（2 ng/ml）使饱和密度增加的程度与PDD（100 ng/ml）相似，但不影响BALB/c 3T3细胞的生长。在两阶段BALB/c 3T3细胞转化试验中，当细胞用TGFβ处理时，我们通过染料转移法测量发现细胞间连接通讯没有变化。然而，转化细胞与周围未转化细胞之间存在选择性通讯；MCA-TGFβ转化细胞彼此之间相互通讯，但不与周围未转化细胞通讯。我们的结果表明，TGFβ在体外具有强大的促肿瘤活性，但这种活性不像佛波酯肿瘤促进剂那样是由细胞间通讯的完全阻断介导的。
