β2-Microglobulin: emerging as a promising cancer therapeutic target

β2-Microglobulin, a MHC class I subunit, is found to act similarly to a prototypical oncogenic factor capable of stimulating growth and progression of various cancers and plays a key regulatory role in stimulating cancer bone metastasis. Free β2M in serum or urine has been regarded as an independent biomarker in several cancers. Specific antibodies to β2M have remarkable tumoricidal activity for both solid tumors and blood malignancies and are shown to be selective to tumor cells, but caused no toxicity in normal cells. These surprising data strongly suggest that β2M is a promising new therapeutic target for human cancers.