The present work investigated the relationship between bacterial pathogenicity factors, cell proliferation and cisplatin sensitivity in the SCLC cell line H69. The pathogenicity factors LPS of gram-negative bacteria and LTA of gram-positive bacteria were incubated with H69 cells in different concentrations and cellular proliferation was measured at different time points. The effect of the pathogenicity factors on the proliferative response of the SCLC cell line, and their effect on cisplatin sensitivity, was investigated. Using automated cell counting and the BrdU assay, a proliferative effect on H69 cells in response to LPS and LTA could be demonstrated. Furthermore, a reduced cisplatin sensitivity could be observed in LPS- or LTA-treated cells. In order to detect possible cisplatin resistance-mediating proteins, gene expression of ABC, EGF, EGFR, IL-8, MDR1 and VEGF under the influence of LPS, LTA and cisplatin was quantified by RT-qPCR. An increased expression of IL-8 and VEGF mRNA was detected in cells treated simultaneously with LPS or LTA and cisplatin. Performing ELISAs for measurement of IL-8 and VEGF protein levels, IL-8, but not VEGF-protein levels were significantly increased in LPS- or LTA-treated cells in the presence of cisplatin. Therefore, experiments with neutralizing antibodies to block the chemokine IL-8 were subsequently performed and showed that LPS-induced cisplatin resistance was reversible by neutralization of IL-8. The pathogenicity factors could induce tumor progression and cisplatin resistance of SCLC in vivo and thus be clinically relevant. LPS and LTA induce increased expression of IL-8 and VEGF in combination with cisplatin and this could result in an increased neovascularisation due to their pro-angiognetic effect and favor tumor proliferation in vivo. SCLC patients suffering from pneumonia could develop cisplatin resistance and show increased tumor progression. In vivo, IL-8 inhibitors and inhibitors of other resistance-triggering proteins could attenuate tumor progression and increase cisplatin sensitivity.