Two sides to colon cancer: mice mimic human anatomical region disparity in colon cancer development and progression

Multi-cohort analysis reveals colorectal cancer tumor location-associated fecal microbiota and their clinical impact

Microbial alterations in different tumor locations of colorectal cancer (CRC) remain unclear. Here, 1,375 fecal metagenomes from six in-house and published datasets were analyzed, including 128 right-sided CRC (rCRC), 168 left-sided CRC (lCRC), 250 rectal cancer (RC), and 829 controls. Firmicutes progressively increase from rCRC, lCRC, to RC, in contrast to the gradual decrease of Bacteroidetes. Tumor location-associated fecal microbes are identified, including Veillonella parvula for rCRC, Streptococcus angionosus for lCRC, and Peptostreptococcus anaerobius for RC, while Fusobacterium nucleatum is enriched in all tumor locations. Tumor location-associated bacteria correlate with patient survival. Clinically, we establish a microbial biomarker panel for each tumor location that accurately diagnoses rCRC (area under the receiver operating characteristic curve [AUC] = 91.59%), lCRC (AUC = 91.69%), or RC (AUC = 90.53%) from controls. Tumor location-specific biomarkers also have higher diagnostic accuracy (AUC = 91.38%) than location-non-specific biomarkers (AUC = 82.92%). Overall, we characterize fecal microbes associated with different CRC tumor locations, highlighting that tumor location should be considered in non-invasive diagnosis.

Differential Actions of Muscarinic Receptor Subtypes in Gastric, Pancreatic, and Colon Cancer

Cancers arising from gastrointestinal epithelial cells are common, aggressive, and difficult to treat. Progress in this area resulted from recognizing that the biological behavior of these cancers is highly dependent on bioactive molecules released by neurocrine, paracrine, and autocrine mechanisms within the tumor microenvironment. For many decades after its discovery as a neurotransmitter, acetylcholine was thought to be synthesized and released uniquely from neurons and considered the sole physiological ligand for muscarinic receptor subtypes, which were believed to have similar or redundant actions. In the intervening years, we learned this former dogma is not tenable. (1) Acetylcholine is not produced and released only by neurons. The cellular machinery required to synthesize and release acetylcholine is present in immune, cancer, and other cells, as well as in lower organisms (e.g., bacteria) that inhabit the gut. (2) Acetylcholine is not the sole physiological activator of muscarinic receptors. For example, selected bile acids can modulate muscarinic receptor function. (3) Muscarinic receptor subtypes anticipated to have overlapping functions based on similar G protein coupling and downstream signaling may have unexpectedly diverse actions. Here, we review the relevant research findings supporting these conclusions and discuss how the complexity of muscarinic receptor biology impacts health and disease, focusing on their role in the initiation and progression of gastric, pancreatic, and colon cancers.