Chemotherapeutic drugs change actin skeleton organization and the expression of beta-thymosins in human breast cancer cells.

Elevated expression of the beta-thymosin isotypes T beta(4), T beta(10), and T(15) appears to be involved in the manifestation of a malignant phenotype of human tumor cells, including those of mammary carcinomas. This has evoked an interest in these peptides as diagnostic/prognostic tumor markers. If increased levels of beta-thymosins correspond to tumor malignancy, the question arises whether tumor growth inhibition induced by chemotherapeutic drugs would reduce their expression. Two human breast cancer cell lines, the estrogen receptor(ER)-positive MCF-7 and the ER-negative MDA-MB231, were thus analyzed for the amount of beta-thymosin mRNAs by RNase protection assay and for the respective peptide levels by HPLC following different hormonal and drug treatments. Both cell lines, growing in medium with 10% FCS, contain T beta(4) (400-500 fg/cell) and Tbeta(10) (about 100 fg/cell), but no T beta(15). Incubating MCF-7 cells with tamoxifen (1 microM) for 5 days resulted in about 80% growth inhibition and in reduction of intracellular T beta(4) and T beta(10) concentrations by about 40%. Levels of T beta(4) and T beta(10)-mRNA were reduced by about 60%. In contrast, cisplatin (2 microM) changed neither the peptide concentrations nor the mRNA levels of beta-thymosins, in spite of marked growth inhibition. In addition, no changes in beta-thymosin expression were observed in MDA-MB231 cells treated with either drug. MCF-7 cells maintained in estrogen-poor medium (10% horse serum) or stimulated to grow with estradiol (1 nM) had Tbeta(4) and T beta(10) concentrations reduced by about 30%, but changes in T beta(4)- and T beta(10)-mRNA levels did not correspond to those of the peptide. Expression of T beta(4) and T beta(10) mRNAs and their peptides is differentially regulated and does not correlate with growth. Instead, reduced beta-thymosin expression may be linked to more intensive TRITC-phalloidin staining of F-actin lining the membrane at sites of intimate cell-cell contacts, while increased beta-thymosin levels appear in cells with more extensive substrate adhesion. This suggests that beta-thymosins play a role in cell surface dynamics.

化疗药物改变人乳腺癌细胞肌动蛋白骨架结构和β-胸腺素的表达。

β-胸腺素同种型Tβ(4)、Tβ(10)和T(15)的高表达似乎与人类肿瘤细胞(包括乳腺癌细胞)的恶性表型表现有关。这引起了人们对这些肽作为诊断/预后肿瘤标志物的兴趣。如果β-胸腺素水平的增加对应于肿瘤恶性程度，那么化疗药物诱导的肿瘤生长抑制是否会降低它们的表达就成了问题。因此，在不同的激素和药物处理后，通过RNase保护试验分析了两种人乳腺癌细胞系，雌激素受体(er)阳性的MCF-7和ER阴性的MDA-MB231的β-胸腺素mRNAs的量，并通过HPLC分析了各自的肽水平。在含10% FCS的培养基中生长的两种细胞系都含有Tβ(4)(400-500 fg/细胞)和Tβ(10)(约100 fg/细胞)，但不含Tβ(15)。将MCF-7细胞与他莫昔芬(1 μm)一起孵育5天，导致约80%的生长抑制和细胞内Tβ(4)和Tβ(10)浓度降低约40%。Tβ(4)和Tβ(10)-mRNA的水平降低了约60%。相反，尽管有明显的生长抑制，顺铂(2微摩尔)既不改变β-胸腺素的肽浓度也不改变其mRNA水平。此外，在用任一种药物处理的MDA-MB231细胞中没有观察到β-胸腺素表达的变化。维持在雌激素缺乏的培养基(10%马血清)中或用雌二醇(1 nM)刺激生长的MCF-7细胞的Tβ(4)和Tβ(10)浓度降低了约30%，但Tβ(4)-和Tβ(10)-mRNA水平的变化与肽的变化不一致。Tβ(4)和Tβ(10)mrna及其肽的表达受到不同程度的调节，与生长无关。相反，β-胸腺素表达的减少可能与细胞间紧密接触部位的膜内层F-肌动蛋白的更强TRITC-phalloidin染色有关，而β-胸腺素水平的增加出现在具有更广泛底物粘附的细胞中。这表明β-胸腺素在细胞表面动力学中起作用。