An article published in May 2022 in the journal Frontiers in Pharmacology describes the effect of calf thymus polypeptides on the regulation of immune function dependent on the intestinal microflora. The mice in which the studies were carried out increased the level of proteins and cytokinins related to immunity and T cells, which effectively slowed down the growth of colon tumors.

Colorectal cancer is the fourth most common cancer and the third most cancer-related death. Depending on the extent of the metastases, the survival in the next 5 years after colorectal tumor removal ranges from 91% to 13%. In addition, 60% of resection patients require further chemotherapy and 10% relapse.

The number of microbes in the gut of an adult person can reach up to 100 trillion, so it is not surprising that the species composition and the substances they produce have an impact on health. The growth of colon tumors is associated with a decrease in the number of beneficial Lactobacillus bacteria and an increase in pathogenic Fusobacterium. The administration of thymic enzymes to mice led to an increase in the abundance of Clostridia, whose metabolites have been associated with the regulation of immunity and the reduction of chronic inflammation. On the other hand, the numbers of Allobacullum and Desulfovibrionales species, which are respectively an indicator of damage to the immune system due to CD-45 deficiency and a source of harmful cytotoxic compounds, have decreased.

The main polypeptides from calf thymus are thymosin, they promote the maturation of T cells by increasing the synthesis of interleukin 7, and thymosin a 1 inhibits the apoptosis of Th and Tc cells. Th cellss promote costimulatory molecules and cytokine expression in dendritic cells, all of which contribute to the activation of T cells. In addition, some of them promote a cytotoxic immune response and others promote a humoral immune response and limit the cytotoxic immune response. Cytotoxic Tc cells are major contributors to the adaptive immune response against cancer and elicit a tumor specific immune response and are therefore important factors in immunotherapy. Thymic enzymes also increased the number of NK cells in the peripheral blood of the mice. As non-specific killer cells, NK cells can promote specific immune responses or kill target cells directly via antibody-dependent pathways. A decrease in the percentage of NK cells in the peripheral blood usually leads to a high incidence of cancer. The last observation was a decrease in the levels of PD-1, PD-L1 and CTLA4 proteins, which are present on the surface of lymphocytes and are responsible for inhibiting their activity, which is related to the reactive response of cancer cells. The administration of antibodies to these proteins is one form of cancer therapy.

In conclusion, researchers showed that in mice, polypeptides from calf thymus are responsible for inhibition of colorectal tumor growth by acting on the intestinal microflora and that they can be used in clinical therapy.

The entire article can be found at: https://www.frontiersin.org/articles/10.3389/fphar.2022.898906/full