pERK/pAkt phenotyping in circulating tumor cells as a biomarker for sorafenib efficacy in patients with advanced hepatocellular carcinoma

Sorafenib is a multikinase inhibitor approved for the treatment of advanced hepatocellular carcinoma (HCC). However, therapeutic response to sorafenib was not equal among HCC patients. Here we present a novel system to provide quantitative information concerning sorafenib-related targets by simultaneous detection of phosphorylated ERK (pERK) and pAkt expressions in circulating tumor cells (CTCs) isolated from HCC patients. Our results showed that 90.0% of patients had a molecular classification of tissues concordant with that of CTCs. CTC counts showed a shaper decline in patients with pERK(+)/pAkt(−) CTCs after two weeks of sorafenib treatment (P < 0.01). Disease control rates were significantly different between patients with pERK(+)/pAkt(−) CTCs (11/15; 73.3%) and those without (13/44; 29.5%) (P < 0.05). Univariate and multivariate analysis indicated pERK(+)/pAkt− CTCs as an independent predictive factor of progression-free survival (PFS) (hazard ratio = 9.389; P < 0.01). PFS correlated with the proportion of pERK(+)/pAkt(−) CTCs (r = 0.968, P < 0.01), and was higher in patients with ≥ 40% pERK(+)/pAkt− CTCs compared to those with < 40% (8.4 vs. 1.3 mo; P < 0.05). In a validation set of twenty HCC patients, CTCs from patients with ≥ 40% pERK(+)/pAkt(−) CTCs had significantly higher inhibition rates of spheroid formation compared to those with < 40% (61.2 vs. 19.8%; P < 0.01). Our findings demonstrated that CTCs can be used in place of tumor tissue for characterization of pERK/pAkt expression. pERK(+)/pAkt(−) CTCs are most sensitive to sorafenib and an independent predictive factor of PFS in HCC patients treated with sorafenib.