GRM1 and breast carcinoma: Parallel, siRNA-mediated inhibition of mGluR1 expression in renal cancer cells impaired tumor growth in vivo, thus suggesting that sustained expression of mGluR1 is necessary for neoplastic transformation and tumor progression (Martino et al. 2013), whereas targeting mGluR1 gene using shRNA-expressing lentiviral construct reduced growth of breast cancer cells both in vitro and in vivo (Speyer et al. 2012).