MMP1 and malignant colon neoplasm: Also, since in vitro studies show that M3R activation strongly induces expression of matrix metalloproteinase-1 (MMP1), an enzyme that degrades extracellular matrix [16] and whose expression correlates with advanced colon cancer stage, metastasis and poor prognosis [17, 18], we explored the association of CHRM3/M3R and MMP1 expression in primary colon cancers.