Th17-type cytokines, IL-6 and TNF-α synergistically activate STAT3 and NF-kB to promote colorectal cancer cell growth

Colorectal cancers (CRCs) frequently exhibit a dense infiltration of cytokine-producing immune and inflammatory cells. However, the specific contributions of each immune cell subset and cytokine to the activation of intracellular pathways that support CRC cell growth remain unclear. In this study, we isolated tumor-infiltrating leukocytes (TILs) and lamina propria mononuclear cells (LPMCs) from both the tumor tissue and adjacent, macroscopically unaffected colonic mucosa of patients undergoing resection for sporadic CRC. We found that culture supernatants from TILs, but not from LPMCs, robustly promoted the proliferation of human CRC cell lines by activating the oncogenic transcription factors signal transducer and activator of transcription 3 (STAT3) and nuclear factor-kappa B (NF-κB).

Characterization of the immune cell composition of TILs and LPMCs revealed comparable percentages of T cells, natural killer T cells, natural killer (NK) cells, macrophages, and B cells between the two populations. However, T cells derived from TILs demonstrated a functional shift, producing significantly higher levels of T helper type 17 (Th17)-related cytokines, including interleukin-17A (IL-17A), IL-17F, IL-21, and IL-22, as well as tumor necrosis factor-alpha (TNF-α) and IL-6, compared with T cells from LPMCs.

Neutralization of individual cytokines, including IL-17A, IL-17F, IL-21, IL-22, TNF-α, or IL-6, did not affect TIL supernatant-induced activation of STAT3 and NF-κB or their pro-proliferative effects on CRC cells. However, simultaneous neutralization of IL-17A and TNF-α, which blocks NF-κB signaling, along with IL-22 and IL-6, which blocks STAT3 signaling, significantly reduced the mitogenic effects of TIL-derived supernatants on CRC cells.

Furthermore, in a mouse model of sporadic CRC, early colonic lesions exhibited elevated production of IL-17A, IL-21, IL-22, TNF-α, and IL-6, alongside enhanced activation of STAT3 and NF-κB. Therapeutic administration of BP-1-102, an orally bioavailable compound that targets STAT3/NF-κB activation and their crosstalk, led to reduced colon tumorigenesis and decreased expression of STAT3/NF-κB-activating cytokines within neoplastic areas.

These findings suggest that therapeutic strategies aimed at the concurrent targeting of STAT3 and NF-κB activation, as well as their interaction, may offer a promising and novel approach for the treatment of CRC.