Human T-cell lymphotropic virus type I (HTLV-I) is the causative agent of adult T-cell leukemia/lymphoma (ATL). ATL is an aggressive proliferation of mature activated T cells associated with a poor prognosis. The combination of the antiviral agents, zidovudine (AZT) and  interferon (IFN), is a potent treatment of ATL. Recently, arsenic trioxide (As) was shown to be an effective treatment of acute promyelocytic leukemia (APL). We have tested the effects of the combination of As and IFN on cell proliferation, cell cycle phases distribution, and apoptosis in ATL-derived or control T-cell lines. A high synergistic effect between IFN and As was observed in ATL-derived cell lines in comparison to the control cell lines, with a dramatic inhibition of cell proliferation, G1 arrest, and induction of apoptosis. Similar results were obtained with fresh leukemia cells derived from an ATL patient. Although the mechanisms involved are unclear, these results could provide a rational basis for combined As and IFN treatments in ATL.

Research has been driven towards finding therapy predictive biomarkers for colorectal cancer (CRC) with a special interest in studying the gut microbiome. Gut microbiome acts not only as a barrier to prevent bacterial invasion and infection, but it also affects the efficacy of hematopoietic-cell transplantation, chemotherapy, and immunotherapy. Recently, immunotherapy, which potentiates the host immune system, has revolutionized cancer therapy in general and CRC treatment specifically by increasing the quality of life and the survival of a subset of patients with this disease. In immunotherapy, the gut microbiome plays an important role in cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) blockade, programmed cell death protein 1 (PD-L1) mediation, and T cell stimulation. As such, this review will cover the role of gut microbiome in CRC, summarize approved immunotherapy treatments for CRC, and focus on the potential use of gut microbiome as a biomarker for immunotherapy.