Prognostic value and multifaceted roles of tetraspanin CD9 in cancer

CD9 is a crucial regulator of cell adhesion in the immune system and plays important physiological roles in hematopoiesis, blood coagulation or viral and bacterial infections. It is involved in the transendothelial migration of leukocytes which might also be hijacked by cancer cells during their invasion and metastasis. CD9 is found at the cell surface and the membrane of exosomes affecting cancer progression and therapy resistance. High expression of CD9 is mostly associated with good patients outcome, with a few exceptions. Discordant findings have been reported for breast, ovarian, melanoma, pancreatic and esophageal cancer, which might be related to using different antibodies or inherent cancer heterogeneity. According to in vitro and in vivo studies, tetraspanin CD9 is not clearly associated with either tumor suppression or promotion. Further mechanistic experiments will elucidate the role of CD9 in particular cancer types and specific conditions.

Automated summary

CD9 is a crucial regulator of cell adhesion in the immune system, playing important physiological roles in hematopoiesis, blood coagulation, and infections. It is involved in leukocytes' transendothelial migration, which may be hijacked by cancer cells during invasion and metastasis. CD9 affects cancer progression and therapy resistance through its presence on cell surface and exosome membranes. The expression of CD9 is generally associated with good patient outcomes, but there are exceptions in breast, ovarian, melanoma, pancreatic, and esophageal cancer, possibly due to different antibodies or cancer heterogeneity. Studies on tetraspanin CD9's role in tumor suppression or promotion are inconclusive, requiring further mechanistic experiments.