Overexpression of G protein-coupled receptor 5D in the bone marrow is associated with poor prognosis in patients with multiple myeloma

Eur J Clin Invest 2012; 42 (9): 953960 Abstract Background G protein-coupled receptor 5D (GPRC5D) is a novel surface receptor. As this new subtype of G protein-coupled receptors was discovered, little is known about the role of this gene. Materials and methods In this retrospective study, we investigated GPRC5D mRNA expression by real-time polymerase chain reaction (RT-PCR) in bone marrow (BM) of 48 patients with multiple myeloma (MM). Results Highly variable levels of GPRC5D (median, 288; quartiles, 17928) were detected in patients with MM, whereas only low expression was detected in normal tissues (median, 1; quartiles, 123). High mRNA expression of GPRC5D correlated positively with high plasma cell count in bone marrow (r = 0.64, P < 0.001), high beta 2-microglobulin (r = 0.42, P = 0.003) and poor-risk cytogenetics: deletion 13q14 (rb-1), P = 0.003; and 14q32 translocation t(4;14)(p16;q32), P = 0.029. GPRC5D mRNA expression showed a significant correlation with overall survival (P = 0.031). The estimated overall survival of patients expressing GPRC5D above or below the median of 288 was 43.9% vs. 70.2% at 48 months. Here, we report, for the first time, the association of GPRC5D expression and cancer. Conclusions Overexpression in poor-risk myeloma, low expression in normal tissues and cell surface expression identify GPRC5D as a potential novel cancer antigen. Our data demonstrate that GPRC5D is a prognostic factor in MM correlating with other major risk factors.