Mutations of candidate tumor suppressor genes at chromosome 3p in intrahepatic cholangiocarcinoma

The genetic status of candidate tumor suppressor genes (TSGs) at chromosome 3p has not yet been elucidated in intrahepatic cholangiocarcinoma (iCCA). Herein, we retrospectively investigated 32 fresh iCCA case samples from a single medical institution to clarify mutations of 11 TSGs by next-generation sequencing. Validation of the mutations was performed on the MassARRAY platform or by high-resolution melting curve analysis. We then integrated the gene mutations into copy number alterations at chromosome 3p that had been generated in a previous study using the same fresh iCCA samples, and correlated the integration results with the clinicopathologic features. Nine of the 32 (28.1%) iCCA patients had gene mutations at chromosome 3p, totaling 11 mutations across five genes. Those included five (15.6%) BAP1 mutations, two each (6.3%) of CACNA2D3 and RASSF1 mutations, and one each (3.1%) of ATG7 and PLCD1 mutations. Six (18.8%) cases had concurrent loss of chromosome 3p and gene mutations. Patients with TSG mutations had shorter disease-free and survival times than those without the mutations. Our data showed that iCCA patients with TSG mutations at chromosome 3p faced an adverse prognosis. BAP1 was the common target of mutational inactivation and may be a principal driver of 3p21 losses.