Carnosic acid increases sorafenib-induced inhibition of ERK1/2 and STAT3 signaling which contributes to reduced cell proliferation and survival of hepatocellular carcinoma cells

Abstract

Hepatocellular carcinoma (HCC) has increasing worldwide incidence but when unresectable lacks curative options. Treatment with a kinase inhibitor Sorafenib (Sf), while initially effective, results in only short increases in patient survival, thus there is a need for improved treatment regimens. Numerous treatment regimens have been explored wherein Sf is combined with other agents, such as non-toxic botanicals like Curcumin or Silibinin. Recently, we have shown that carnosic acid (CA), a component of the food preservative Rosemary Extract, can markedly enhance the cytotoxic actions of Sf in several cell lines derived from HCC, but not in the cell line Hu1545 derived from normal hepatocytes. CA has been shown to enhance Sf-induced cell death in the neoplastic cell lines, principally due to the composite of increased apoptosis and cytotoxic autophagy. In the present study we focused on the mechanisms that underlie the reduced proliferation and survival of HCC cells when CA is added to Sf and how this relates to the increase in Sf-induced DNA damage as well as to the elevation of cytoplasmic levels of reactive oxygen species (ROS). Importantly, the elevation of ROS levels induced by Sf was increased by adding CA. We found that CA enhanced Sf-induced prolongation of cell cycle, and the overall decrease in cell growth was associated with reduced activation of both STAT3 transcription factor (TF) and extracellular signal-regulated protein kinase (Erk)1/2. Our data suggest that a regimen incorporating CA, an inexpensive and non-toxic food additive, in the treatment of advanced HCC merits clinical evaluation.

Adverse Toxic Effects of Tyrosine Kinase Inhibitors on Non-Target Zebrafish Liver (ZFL) Cells

“…In contrast to our results, the European Medicines Agency (EMEA) reported that NIL did not induce DNA single-strand breaks in the mouse L5178Y cell line evaluated by the comet assay [ 60 ]. Moreover, the exposure to SOR did not significantly increase DNA double strand breaks, as detected by the neutral comet assay in vitro in human colon adenocarcinoma HT-29 cell line treated with 16 uM for 12 h [ 61 ] and in HepG2 cells treated with 1 µM for 24 h, as detected by the alkaline comet assay [ 62 ]. In contrast, SOR induced DNA damage in vitro in Huh7 [ 62 ], A549 and MCF-7 [ 63 ] cells and in the liver of male albino rats treated with 10 mg/kg body weight daily for two weeks [ 64 ].…”

“…Moreover, the exposure to SOR did not significantly increase DNA double strand breaks, as detected by the neutral comet assay in vitro in human colon adenocarcinoma HT-29 cell line treated with 16 uM for 12 h [ 61 ] and in HepG2 cells treated with 1 µM for 24 h, as detected by the alkaline comet assay [ 62 ]. In contrast, SOR induced DNA damage in vitro in Huh7 [ 62 ], A549 and MCF-7 [ 63 ] cells and in the liver of male albino rats treated with 10 mg/kg body weight daily for two weeks [ 64 ]. Diab et al [ 64 ] indicated that DNA damage assessed by the comet assay in vivo was most likely of oxidative origin, as simultaneous treatment of male albino rats with SOR and antioxidants significantly reduced DNA damage induced by SOR.…”