Bacteriophages can be used effectively to cure bacterial infections. They are known to be active against bacteria but inactive against eukaryotic cells. Nevertheless, novel observations suggest that phages are not neutral for higher organisms. They can affect physiological and immunological processes which may be crucial to their expected positive effects in therapies. Bacteriophages are a very differentiated group of viruses and at least some of them can influence cancer processes. Phages may also affect the immunological system. In general, they activate the immunological response, for example cytokine secretion. They can also switch the tumor microenvironment to one advantageous for anticancer treatment. On the other hand, bacteriophages are used as a platform for foreign peptides that may induce anticancer effects. As bacterial debris can interfere with bacteriophage activity, phage purification is significant for the final effect of a phage preparation. In this review, results of the influence of bacteriophages on cancer processes are presented which have implications for the perspective application of phage therapy in patients with cancer and the general understanding of the role of bacteriophages in the human organism.

Bacteriophages constitute a serious alternative to antibiotic therapy of bacterial infections. They are also extremely numerous entities: phages can be found in almost all places on Earth and are constantly present in human and animal bodies. Observations of the effect of therapeutic staphylococcal phages and their bacterial hosts on melanoma migration in vitro are reported in this article. Together with bacteriophage preparations, disrupted Staphylococci (host strains) were investigated to compare the effects of bacteria with those of bacteriophages. Migration was decreased by all the investigated preparations in various ways and this was rather due to the activity of the bacterial components. Importantly, none of the investigated bacteriophage or bacterial preparations induced an increase in the migration activity of melanoma cells, which is important from the perspective of the therapeutic use of phage lysates. The possible presence of staphylococcal enterotoxins in the therapeutic bacteriophage preparations was also verified. All the studied therapeutic bacteriophage preparations were negative for the Staphylococcal enterotoxins A, B, C, D, and E (i.e., the enterotoxin content was less than 0.2-0.5 ng/ml).