Regulation of transforming growth factor beta1 by radiation in cells of two human breast cancer cell lines.

We have investigated the mechanisms by which radiation inhibits proliferation of human breast cancer cells in culture. Radiation, within the dose range used for treatment of humans, decreased the rate of proliferation of estrogen-independent MDA-MB-231 cells more effectively than it did that of estrogen-dependent MCF-7 cells. The rate of proliferation of MDA-MB-231 cells was also inhibited to a greater extent than that of MCF-7 cells by purified TGFB1. Using an ELISA specific for activated TGFB1, we found that conditioned medium from irradiated MDA-MB-231 or MCF-7 cells contained twofold more TGFB1 than that from nonirradiated cells. Conditioned medium from irradiated breast cancer cells, but not from nonirradiated cells, inhibited the growth of untreated MDA-MB-231 cells. The inhibitory activity was blocked by an anti-TGFB1 neutralizing antibody. An approximately twofold increase in the TGFB1 mRNA in irradiated cells compared to controls was found using semiquantitative reverse-transcriptase PCR. Last, the mRNA for insulin-like growth factor binding protein 3, a reported target of the cell inhibitory activity of TGFB1, was increased threefold upon irradiation. Our results demonstrate that the TGFB1 is increased after irradiation and that the activation of the TGFB1 signaling pathway may sensitize cells to the effects of radiation.

Characterization of mild whole-body hyperthermia protocols using human breast, ovarian, and colon tumors grown in severe combined immunodeficient mice.

OBJECTIVE: We have shown that one treatment of fever-like whole body hyperthermia (WBH) on mice bearing human breast tumors results in a tumor growth delay. Our goal was to repeat this study in mice bearing human ovarian or colon tumors. We further evaluated this WBH protocol by performing multiple and interrupted WBH treatments. METHODS: Human tumors were grown in severe combined immunodeficient (SCID) mice. For WBH, core body temperatures were maintained at 39.8+/-0.2 degrees C for 6-8 hours. Multiple treatments were given 6-7 days apart. Interrupted WBH consisted of three 2-hour heatings, 15 minutes apart. Tumor growth time (TGT) was the number of days to grow 1.5 or 2 times in volume. RESULTS: For WBH-treated ovarian tumors, TGT was 12+/-1.2d, compared with 5.0+/-0.1d for untreated mice (P < 0.05). For colon tumors with one WBH treatment TGT was 4.4+/-1.1d. Two and three treatments had TGTs of 9+/-2.3d and 8+/-1.6d. For the untreated tumors, TGT was 2+/-0.7d (P < 0.01 for one, two, and three treatments). Histological examination indicated that one and two treatments were associated with cellular damage within the tumors. With a slower growing colon tumor, the TGT was 24+/-3.3d with three WBH treatments, compared with 14+/-1.8d for controls (P < 0.01). The TGT of breast tumors treated with interrupted WBH was not significantly different than the noninterrupted, with TGT of 7.3+/-0.8d and 6.2+/-1.0d, respectively. CONCLUSIONS: These data illustrate that WBH causes a tumor growth delay in mice bearing human ovarian and colon tumors. This response is enhanced with a second treatment of WBH. Interrupted and noninterrupted WBH give comparable anti-tumor results. We will continue to evaluate WBH in various animal models to optimize its potential for clinical administration and maximize the anti-tumor response.

Identification of bone morphogenetic proteins and their receptors in human breast cancer cell lines: importance of BMP2.

The most frequent site of breast cancer metastasis is bone suggesting that some breast cancers express proteins that facilitate this process. We evaluated whether a highly metastatic breast cancer cell line, MDA-MB-231, and a less metastatic breast cancer cell line, MCF-7, contain bone morphogenetic proteins (BMP). Semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) demonstrated that MDA and MCF-7 cells contain mRNAs for BMP receptors IA, IB and II. RT-PCR indicated the presence of mRNAs for BMPs 2 and 3 but not 4 and 7 in breast cells. Using a RT-PCR strategy with molecular beacons, we found that the mRNA for BMP2 in MDA cells was decreased by 75% after a sublethal dose of radiation. An ELISA using an antibody specific for BMP2 demonstrated that BMP2 protein was reduced after radiation of MDA cells. The mRNA for BMP2 was expressed to a lesser extent in MCF-7 cells than MDA cells and was not altered after radiation treatment of MCF-7 cells as demonstrated by molecular beacon RT-PCR. Recombinant human BMP2 decreased the proliferation of MDA cells to a greater extent than MCF-7 cells. These results expand the number of tissues that contain BMPs and demonstrate the effect of this signalling pathway of the growth state of these tissues.