Article Text
Abstract
Objective We investigated the mutational landscape of mammalian target of rapamycin (mTOR) signalling cascade in hepatocellular carcinomas (HCCs) with chronic HBV background, aiming to evaluate and delineate mutation-dependent mechanism of mTOR hyperactivation in hepatocarcinogenesis.
Design We performed next-generation sequencing on human HCC samples and cell line panel. Systematic mutational screening of mTOR pathway-related genes was undertaken and mutant genes were evaluated based on their recurrence. Protein expressions of tuberous sclerosis complex (TSC)1, TSC2 and pRPS6 were assessed by immunohistochemistry in human HCC samples. Rapamycin sensitivity was estimated by colony-formation assay in HCC cell lines and the treatment was further tested using our patient-derived tumour xenograft (PDTX) models.
Results We identified and confirmed multiple mTOR components as recurrently mutated in HBV-associated HCCs. Of significance, we detected frequent (16.2%, n=18/111) mutations of TSC1 and TSC2 genes in the HCC samples. The spectrum of TSC1/2 mutations likely disrupts the endogenous gene functions in suppressing the downstream mTOR activity through different mechanisms and leads to more aggressive tumour behaviour. Mutational disruption of TSC1 and TSC2 was also observed in HCC cell lines and our PDTX models. TSC-mutant cells exhibited reduced colony-forming ability on rapamycin treatment. With the use of biologically relevant TSC2-mutant PDTXs, we demonstrated the therapeutic benefits of the hypersensitivity towards rapamycin treatment.
Conclusions Taken together, our findings suggest the significance of previously undocumented mutation-dependent mTOR hyperactivation and frequent TSC1/2 mutations in HBV-associated HCCs. They define a molecular subset of HCC having genetic aberrations in mTOR signalling, with potential significance of effective specific drug therapy.
- HEPATOCELLULAR CARCINOMA
- GENE MUTATION
- MUTATION SCREENING
- HEPATITIS B
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Footnotes
DWHH and LKC contributed equally.
Contributors IOLN and CMW provided study concept and design. DWHH, LKC, MXL and YTC collected and analysed the data. DWHH, LKC, MXL, YTC, IOLN and CMW interpreted the data. LKC, IMJX and YTC performed the experiments. ILOL, DTWY, PWYL, CNT, VWLT, RTPP and TTC collected the patients' samples. LKC, DWHH, IOLN and CMW wrote the manuscript. All authors approved the final version of manuscript.
Funding The study was supported by Hong Kong Research Grants Council General Research Fund (17116414), Research Grants Council Theme-based Research Scheme (T12-704116-R), SK Yee Medical Research Fund 2011, University Development Fund of the University of Hong Kong and Lee Shiu Family Foundation. IOLN is Loke Yew Professor in Pathology.
Competing interests None declared.
Ethics approval Institutional Review Board of the University of Hong Kong/Hospital Authority Hong Kong West Cluster.
Provenance and peer review Not commissioned; externally peer reviewed.
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