The downregulation of the expression of RARγ in macrophages is related to the poor prognosis of colorectal cancer patients. Lactic acid from tumors promotes H3K18 lactation thereby inhibiting the transcription of the RARγ gene in macrophages, increasing the level of IL-6, and promoting the tumor progression of macrophages by activating signal transductors and transcription activator 3 (STAT 3) signal transduction in CRC cells. The gene discussed is IL6; the disease is colorectal cancer.