Inhibition of c-Met promoted apoptosis, autophagy and loss of the mitochondrial transmembrane potential in oridonin-induced A549 lung cancer cells

OBJECTIVE

Herein, inhibition of hepatocyte growth factor receptor, c-Met, significantly increased cytochrome c release and Bax/Bcl-2 ratio, indicating that c-Met played an anti-apoptotic role. The following experiments are to elucidate this anti-apoptotic mechanism, then the effect of c-Met on autophagy has also been discussed.

METHODS

Investigated was the influence of c-Met on apoptosis, autophagy and loss of mitochondrial transmembrane potential (Δψm), and the relevant proteins were examined.

KEY FINDINGS

First, we found that activation of extracellular signal-regulated kinase (ERK), p53 was promoted by c-Met interference. Subsequent studies indicated that ERK was the upstream effector of p53, and this ERK-p53 pathway mediated release of cytochrome c and up-regulation of Bax/Bcl-2 ratio. Secondly, the inhibition of c-Met augmented oridonin-induced loss of mitochondrial transmembrane potential (Δψm), resulting apoptosis. Finally, the inhibition of c-Met increased oridonin-induced A549 cell autophagy accompanied by Beclin-1 activation and conversion from microtubule-associated protein light chain 3 (LC3)-I to LC3-II. Activation of ERK-p53 was also detected in autophagy process and could be augmented by inhibition of c-Met. Moreover, suppression of autophagy by 3-methyladenine (3-MA) or small interfering RNA against Beclin-1 or Atg5 decreased oridonin-induced apoptosis. Inhibition of apoptosis by pan-caspase inhibitor (z-VAD-fmk) decreased oridonin-induced autophagy as well and Loss of Δψm also occurred during autophagic process.

CONCLUSION

Thus, inhibiting c-Met enhanced oridonin-induced apoptosis, autophagy and loss of Δψm in A549 cells.

The evolving landscape of therapeutic drug development for hepatocellular carcinoma

Currently, only one drug, sorafenib, is FDA approved for the treatment of advanced hepatocellular carcinoma (HCC), achieving modest objective response rates while still conferring an overall survival benefit. Unlike other solid tumors, no oncogenic addiction loops have been validated as clinically actionable targets in HCC. Outcomes of HCC could potentially be improved if critical molecular subclasses with distinct therapeutic vulnerabilities can be identified, biomarkers that predict recurrence or progression early can be determined and key epigenetic, genetic or microenvironment drivers that determine best response to a specific targeting treatment can be uncovered. Our group and others have examined the molecular heterogeneity of hepatocellular carcinoma. We have developed a panel of patient derived xenograft models to enable focused pre-clinical drug development of rationally designed therapies in specific molecular subgroups. We observed unique patterns, including synergies, of drug activity across our molecularly diverse HCC xenografts, pointing to specific therapeutic vulnerabilities for individual tumors. These efforts inform clinical trial designs and catalyze therapeutic development. It also argues for efficient strategic allocation of patients into appropriate enriched clinical trials. Here, we will discuss some of the recent important therapeutic studies in advanced HCC and also some of the potential strategies to optimize clinical therapeutic development moving forward.

Effect of c-Met inhibitor SU11274 on hepatocellular carcinoma cell growth

c-Met, a type of receptor tyrosine kinase, may be significantly associated with the progression of hepatocellular carcinoma (HCC). In addition, des-γ-carboxyprothrombin (DCP) has been found to interact with c-Met and activate HCC cell growth. Therefore, the functional inhibition of c-Met expressed on HCC cells should arrest HCC cell growth. The present study found that the c-Met inhibitor SU11274 suppressed HCC cell growth by inhibiting the activation of c-Met. Furthermore, this inhibitor also neutralized the activation of HCC cell growth resulting from the addition of DCP. These results suggest that the functional inhibition of c-Met might be a target for the development of chemotherapeutic agents for HCC, and especially those that are positive for expression of DCP.