Some radiobiological consequences of mycoplasma contamination of mammalian cells in tissue culture

The effect of mycoplasma on the autocrine stimulation of human small cell lung cancer in vitro by bombesin and beta-endorphin

The tumor stem cell clonogenic assay was utilized to investigate the autocrine growth response of small cell lung cancer (SCLC) to bombesin (BN) and beta-endorphin (beta-E). Mycoplasma contamination was detected in the human SCLC cell line NCl-H345 by a nucleic acid hybridization assay which detects mycoplasma ribosomal RNA. Clonogenic assays of mycoplasma (+) cells were compared to assays of the same cell line following treatment for mycoplasma. Concentrations of beta-E ranging from 0.1nM to 25nM or BN (0.1nM-100nM) were added to cells, media and agarose and applied to prepared base layers. Following incubation for 12-14 days at 37 degrees C, the degree of clonal growth stimulation was determined by colony counts greater than or equal to 42 mu. The non-infected cell population grew in the presence of 25nM BN up to 69% over control growth. The infected cells, however, did not grow more than 27% above control. In the presence of 10nM beta-E, colony counts of non-infected cells exceeded the control values by up to 187% whereas the mycoplasma (+) colonies did not grow more than 20% over the control values. These results indicate a marked reduction in the response of SCLC cell lines to the peptides BN and beta-E when infected with mycoplasma. Since infecting mycoplasma typically adhere to cellular membranes, these adherent mycoplasma may interfere with membrane receptors or alter signal transduction, thus, inhibiting the development of the autocrine response.