Therapeutic methods for administering gut microbiota and oncolytic viruses to a subject are provided. The gut microbiota serve to pre-condition, the subject's immune system to antitumor responses and augments anticancer activity of the oncolytic vims. Combinations of the gut. microbiota and viruses and uses thereof for treating and preventing cancer are provided. The present disclosure also provides methods for building elite responder selection platforms through hierarchical clustering analysis of genomic profiles for human gut microbiome.