Screen p53 mutations in hepatocellular carcinoma by FASAY: a novel splicing mutation

Targeted sequencing reveals the mutational landscape responsible for sorafenib therapy in advanced hepatocellular carcinoma

Rationale: The existence of primary and acquired drug resistance is the main obstacle for the effect of multi-kinase inhibitor sorafenib and regorafenib in advanced hepatocellular carcinoma (HCC). However, plenty of patients did not significantly benefit from sorafenib treatment and little is known about the mechanism of drug resistance. Methods: Laser capture microdissection was used to acquire matched normal liver and tumor tissues on formalin-fixed paraffin-embedded specimens collected before sorafenib therapy from the first surgery of 119 HCC patients. Ultra-deep sequencing (~1000×) targeting whole exons of 440 genes in microdissected specimens and siRNA screen in 7 cell lines were performed to find mutations associated with differential responses to sorafenib. Patient-derived xenograft models were employed to determine the role of TP53 in response to sorafenib. Lentiviruses harboring wild-type and c.G52C-mutant OCT4 were applied to explore the function of OCT4 in resistance to sorafenib. ChIP-PCR assay for analysis of OCT4 transcriptional activity was performed to explore the affinity with the KITLG promoter. Statistical analyses were used to associate levels of p53 and OCT4 with tumor features and patient outcomes. Results: Total 1,050 somatic mutations and 26 significant driver genes were identified. SiRNA screening in 7 HCC cell lines was further performed to identify mutations associated with differential responses to sorafenib. A recurrent nonsynonymous mutation c.G52C in OCT4 (OCT4 ^mut) was strongly associated with good response to sorafenib, whereas the stop-gain mutation in TP53 showed the opposite outcome both in vitro and in vivo. OCT4 ^wt-induced stem cell factor (encoded by KITLG gene, SCF) expression and cross-activation of c-KIT/FLT3-BRAF signals were identified indispensably for sorafenib resistance, which could be reversed by the combination of c-KIT tyrosine kinase inhibitors or neutralizing antibody against SCF. Mechanistically, an OCT4 binding site in upstream of KITLG promoter was identified with a higher affinity to wildtype of OCT4 rather than G52C-mutant form, which is indispensable for OCT4-induced expression of KITLG and sorafenib resistance. Conclusion: Our study reported a novel somatic mutation in OCT4 (c.G52C) responsible for the sorafenib effect, and also shed new light on the treatment of HCC through the combination of specific tyrosine kinase inhibitors according to individual genetic patterns.

Treating hepatocellular carcinoma progression following first-line sorafenib: therapeutic options and clinical observations

Despite the established efficacy of sorafenib in advanced hepatocellular carcinoma (HCC), a significant number of sorafenib-treated patients experience disease progression. Current guidelines recommend either best supportive care or clinical trial enrollment for this population. As such, there remains an unmet need for tolerable, life-prolonging strategies in the second-line setting. New information regarding the molecular pathogenesis of resistance to antiangiogenic therapy and positive post-progression experience with antiangiogenics in other tumor types has led to trials investigating the effect of continued use of sorafenib, alone or combined with other agents. Trials investigating the effect of switching from sorafenib to alternate antiangiogenic agents, phosphatidylinositol 3 kinase/AKT/mammalian target of rapamycin inhibitors, or cMet inhibitors are also underway. As these data emerge, clinicians may consider a new paradigm for managing advanced HCC. This article briefly reviews the mechanisms of disease resistance to antiangiogenic therapy as a vehicle for discussing clinical strategies to prolong survival in patients with advanced HCC that are currently employed at our institutions or are under investigation. Key ongoing trials investigating the use of molecularly targeted therapies in patients with progressive disease are also highlighted.

TP53 status and response to treatment in breast cancers

The p53 wild-type protein plays an important role in cells as is shown by its fine regulation at different levels. Since its discovery, numerous mutations have been described. In breast cancers, p53 is mutated in almost 30% of cases, with a higher frequency in some tumor subtypes. TP53 mutation is reported to be a factor for good prognosis in some studies, while in others it is a factor for poor prognosis. The explanation for these different results could be linked to the fact that the studies were performed on different tumor types and with different therapy regimens.