• Hiromichi Matsuoka, Tokuzo Arao, Chihiro Makimura, Masayuki Takeda, Hidemi Kiyota, Junji Tsurutani, Yoshihiko Fujita, Kazuko Matsumoto, Hideharu Kimura, Masatomo Otsuka, Atsuko Koyama, Chiyo K Imamura, Yusuke Tanigawara, Takeharu Yamanaka, Kyoko Tanaka, Kazuto Nishio, and Kazuhiko Nakagawa.
• Department of Medical Oncology, Kinki University Faculty of Medicine, and Department of Palliative Care, Sakai Hospital, Osaka 589-8511, Japan.
• Oncol. Rep. 2012 May 1; 27 (5): 1393-9.

AbstractGenetic differences in individuals with regard to opioid-receptor signaling create clinical difficulties for opioid treatment; consequently, useful pharmacodynamic and predictive biomarkers are needed. In this prospective study, we studied gene expression changes in peripheral blood leukocytes using a microarray and real-time RT-PCR analysis to identify pharmacodynamic biomarkers for monitoring the effect of morphine in a cohort of opioid-treatment-naïve cancer patients. We also examined genetic variations in opioid receptor mu 1 (OPRM1, 118A→G) and catechol-O-methyltransferase (COMT, 472G→A) to evaluate predictive biomarkers of the treatment outcome of morphine. The plasma concentration of morphine was measured using a liquid chromatography-tandem mass spectrometry method. Microarray analysis revealed that the mRNA expression levels of arrestin β 1 (ARRB1) were significantly down-regulated by morphine treatment. Real-time RT-PCR analysis against independent samples confirmed the results (P=0.003) and changes during treatment were negatively correlated with the plasma morphine concentration (R=-0.42). No correlation was observed between the genotype of OPRM1 and morphine treatment; however, the plasma concentration of morphine and the required dose of morphine were significantly lower for the A/A genotype of COMT (vs. A/G+G/G, P=0.008 and 0.03). We found that changes in the expression of ARRB1 may be a novel pharmacodynamic biomarker and the COMT 472G→A genotype may be a predictive biomarker of the response to morphine treatment.

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