Messenger RNA expression of resistance factors in human tumor cell lines after single exposure to radiation.

Resistance of tumor cells to chemotherapeutic drugs can not only be caused by treatment with antineoplastic agents but also by radiotherapy. The aim of this study was to analyze whether ionizing radiation can influence the mRNA expression of proteins which have been found to be involved in drug resistance of tumor cells. Human tumor cell lines (MCF-7, LXF and Sk-Mel) were treated with single doses of irradiation (5, 10 and 20 Gy).

Effects of single doses of irradiation on the expression of resistance-related proteins in murine NIH 3T3 and human lung carcinoma cells.

In this report the effects of single doses of ionizing radiation on the mRNA expression of several proteins involved in multiple drug resistance were analyzed. Murine NIH 3T3 cells treated with single doses of 5, 10 and 20 Gy during the time interval from 1.5 to 72 h after irradiation were compared with their corresponding controls at the same points of time.

Induction of resistance-proteins and oncoproteins in murine and human tumor-cell lines after irradiation.

The aim of this investigation was to analyze whether or not ionizing radiation can induce the expression of resistance- and oncoproteins in murine sarcoma 180 cells and several human carcinoma cell lines. For assessment of the proteins the streptavidin-biotin peroxidase-complex method was performed using specific antibodies. Expression of glutathione S-transferase-pi and thymidylate-synthase was increased after a single dose of irradiation which was accompanied by a lower sensitivity against cisplatin and 5-fluorouracil.

Associated expression of protein kinase C with resistance to doxorubicin in human lung cancer.

The expression of protein kinase C (PKC) in 83 untreated solid human non-small cell lung carcinomas was determined and its correlation with inherent resistance to doxorubicin, with the expression of P-glycoprotein (P-170), and with the expression of glutathione S-transferase-pi (GST-pi) was analysed. Doxorubicin resistance was measured using an in vitro short-term test. The expression of PKC, P-170 and GST-pi was assessed immunohistochemically.

Reversal of doxorubicin-resistance in solid tumors by clomipramine.

Resistance to cytotoxic treatment is a major obstacle to more successful cancer treatment, and approaches to overcome the drug resistance of tumors have received much attention in recent years. In the present in vivo study the psychotropic drug clomipramine was used as chemosensitizer in the doxorubicin (DOX)-resistant L 1210 cell line growing as solid tumors in mice. A significant reduction in the growth of DOX-resistant tumors was observed after treatment with clomipramine and DOX (p = 0.