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High Calcium Content of Pleiotropic Drug-resistant P388 and K562 Leukemia and Chinese Hamster Ovary Cells¹

Cancer Chemotherapy Center, Japanese Foundation for Cancer Research, Kami-Ikebukuro 1-37, Toshima-ku, Tokyo 170, Japan

The calcium content of pleiotropic drug-resistant tumor cells was estimated and compared with that of the parent tumor lines. P388 leukemia cells resistant to vincristine and Adriamycin contained more calcium (1.5- to 1.8-fold) in the cells and on the cell surface than the parent P388 cells. Similar results were obtained with human K562 myelogenous leukemia cells resistant to vincristine and also with Chinese hamster ovary cells resistant to colchicine. However, the calcium content of P388 cells resistant to 5-fluorouracil was almost the same as that of the parent P388 cells. The calmodulin content of pleiotropic resistant tumor lines and a 5-fluorouracil-resistant tumor line was almost the same as that of the corresponding parent lines. The isolated plasma membrane of K562 cells resistant to vincristine contained approximately 1.5-fold higher calcium than the parent cells. These results indicate that the higher cellular calcium content might be a characteristic phenotype of pleiotropic resistant tumor lines.

¹ This work was supported by a Grant-in-Aid (57010075) for Cancer Research from the Ministry of Education, Science, and Culture, Japan. A preliminary communication of a part of the present study has been reported (33), and this study was presented at the Seventy-Fifth Annual Meeting of the American Association for Cancer Research, Toronto, Ontario, Canada (23).

² To whom requests for reprints should be addressed.

Received 8/ 1/83. Accepted 7/30/84.