GPRC5D is a promising marker for monitoring the tumor load and to target multiple myeloma cells.

In a comparison of gene expression profile in unsorted bone marrow (BM) samples from patients with multiple myeloma (MM), acute leukemia, and diffuse large B-cell lymphoma infiltrating the BM, the leading myeloma distinguishing gene was GPRC5D. This gene was highly expressed in BM samples from the 10 MM cases examined as opposed to minimal expression in samples from the eight cases with other hematological malignancies. Moreover, following antimyeloma treatment the expression of GPRC5D decreased several folds. The strong and selective expression of GPRC5D in MM cells makes this gene and its encoded surface protein as promising markers for monitoring the tumor load and hopefully also as targets for antimyeloma antibodies.