Hepatocellular carcinoma (HCC) is the fifth most common malignancy [
1], and the third cause of cancer-related mortality worldwide [
2]. The overall incidence of HCC is fairly high and steadily rising in both the developed and the developing world, on account of the prevalence of the two major risk factors, hepatitis B virus (HBV) and hepatitis C virus (HCV) [
3]. Despite the poor understanding of how HBV and/or HCV lead to HCC, some antiviral agents have been found to exhibit anticarcinogenic effects [
4]. Matrine, an alkaloid isolated from the root of Sophora subprostrata, is originally used in the treatment of enteritis, hepatitis, hepatic fibrosis and hypertension in China [
5]. Matrine is also found to induce cell death in many kinds of cancer cells, including cervical cancer, leukemia, gastric cancer, lung cancer and breast cancer [
6‐
10], and thus is considered as a promising drug for cancer therapy.
Caspase-dependent apoptosis is the best-known modality of programmed cell death (PCD) [
11]. Conventional anticancer agents, regardless of their distinct targets and mechanisms, primarily induce cell death via caspase-dependent apoptosis [
12,
13]. Meanwhile, cancer cells are usually sensitive to caspase-dependent apoptotic induction initially, but eventually they become drug-resistant due to the dysregulation of apoptotic machinery, manifested as the over-expression of anti-apoptotic proteins and the defects in pro-apoptotic factors [
14,
15]. Therefore, developing new drugs and methods that can specifically treat drug-resistant cancers is an urgent task for saving lives.
Fortunately, increasing evidence shows that PCD can also happen in the presence of the pan-caspase inhibitor z-VAD-fmk [
16,
17]. In C. elegans, some cells succumb to developmental cell death in a caspase-independent pathway [
18]. N-methyl-N’-nitro-N-nitrosoguanidine (MNNG) can also induce caspase-independent PCD (ciPCD) in MEF cells [
19]. However, understanding of how cells actually die during ciPCD remains limited. Recently, strong evidence of the important role of AIF in ciPCD, via its releasing from mitochondria into nucleus [
20,
21], has been shown in studies performed with alkylating DNA damage agents [
22,
23]. Despite the prominent role of AIF in ciPCD signaling, the mechanisms upstream of AIF releasing are still poorly defined. Previous studies have suggested that a member of the bcl-2 family, Bid, facilitates the insertion of Bak or Bax into mitochondrial membrane to form functional oligomers, which results in the depolarization of the inner mitochondrial membrane and the subsequent AIF translocate from mitochondria to nucleus [
24,
25]. Thus, Bid regulates AIF translocation is involved in ciPCD, and might be a potential mechanism for developing effective drug to induce cancer cell death. HepG2 cell line is well characterized of hepatocellular carcinoma and is widely used in the study [
26,
27]. Therefore, we investigated the mechanisms of matrine-induced cell death in hepacellular carcinoma cell line HepG2
in vitro and subcutaneous xenograft tumors in nude mice
in vivo. We found that caspase-dependent and caspase-independent PCD occurred in HepG2, accompanied by mitochondrial transmembrane potential losing, ROS production, cytochrome c and AIF released from the mitochondria. What’ more, AIF was required in caspase-independent cell death and its translocation was prevented by Bid inhibitor BI-6C9, Bid siRNA and ROS scavenger Tiron. In the
in vivo study, matrine significantly attenuated tumor growth with AIF release from mitochondria and accumulation in nucleus in nude mice. These findings suggest that matrine may provide a new selectivity for hepatocarcinoma therapy through the induction of AIF-mediated ciPCD.