Influence of 12 antibiotics on antitumor immunity in BALB/c-mice.

The effects of 7 days' chemotherapy with penicillin G, piperacillin, mezlocillin, cephalothin, cefamandole, cefotaxime, gentamicin, amikacin, streptomycin, rifampicin, doxycycline, and clindamycin on local tumor growth and metastatic lung colonization were studied in an experimental tumor model (BALB/c-mouse-sarcoma L-1). The antibiotic dosages administered to mice were calculated on a body weight basis from doses recommended for human therapy. Except for mezlocillin, piperacillin, rifampicin and doxycycline, antibiotic treatment did not significantly influence local tumor growth, lung colonization and immune functions. Whereas mezlocillin exerted positive (tumor suppressive) or negative (tumor promoting) effects depending on the chemotherapy schedule, tumor growth and spread were significantly increased independent of the timing scheme after rifampicin or doxycycline treatment. Since certain immune functions (delayed type hypersensitivity; proliferation of spleen lymphocytes) were significantly suppressed after administration of mezlocillin, rifampicin and doxycycline, a correlation between antimicrobial chemotherapy and tumor progression may be possible.