Tetracycline /J01A/, penicillin /J01C/ and particularly narrow spectrum, beta- lactamase resistant penicillin /J01CF/ appears to be promoting the development of certain hematological malignancies (HL, NHL, MM), while other groups of antibiotics might inhibit the oncogenic process (cephalosporin, J01D) through the modification of gut flora. This evidence concerns the gene LACTB and non-Hodgkin lymphoma.