Haprolid Inhibits Tumor Growth of Hepatocellular Carcinoma through Rb/E2F and Akt/mTOR Inhibition

Abstract

Background: Hepatocellular carcinoma (HCC) represents a major health burden with limited curative treatment options. There is a substantial unmet need to develop innovative approaches to impact the progression of advanced HCC. Haprolid is a novel natural component isolated from myxobacteria. Haprolid has been reported as a potent selective cytotoxin against a panel of tumor cells in recent studies including HCC cells. The aims of this study are to evaluate the antitumor effect of haprolid in HCC and to understand its underlying molecular mechanisms. Methods: The efficacy of haprolid was evaluated in human HCC cell lines (Huh-7, Hep3B and HepG2) and xenograft tumors (NMRI-Foxn1 nu mice with injection of Hep3B cells). Cytotoxic activity of haprolid was determined by the WST-1 and crystal violet assay. Wound healing, transwell and tumorsphere assays were performed to investigate migration and invasion of HCC cells. Apoptosis and cell-cycle distribution were measured by flow cytometry. The effects of haprolid on the Rb/E2F and Akt/mTOR pathway were examined by immunoblotting and immunohistochemistry. Results: haprolid treatment significantly inhibited cell proliferation, migration and invasion in vitro. The epithelial-mesenchymal transition (EMT) was impaired by haprolid treatment and the expression level of N-cadherin, vimentin and Snail was downregulated. Moreover, growth of HCC cells in vitro was suppressed by inhibition of G1/S transition, and partially by induction of apoptosis. The drug induced downregulation of cell cycle regulatory proteins cyclin A, cyclin B and CDK2 and induced upregulation of p21 and p27. Further evidence showed that these effects of haprolid were associated with Rb/E2F downregulation and Akt/mTOR inhibition. Finally, in vivo nude mice experiments demonstrated significant inhibition of tumor growth upon haprolid treatment. Conclusion: Our results show that haprolid inhibits the growth of HCC through dual inhibition of Rb/E2F and Akt/mTOR pathways. Therefore, haprolid might be considered as a new and promising candidate for the palliative therapy of HCC.

Centromere protein N may be a novel malignant prognostic biomarker for hepatocellular carcinoma

“…In papillary carcinoma (PTC), CITED1-meditaed interference of p21 and p27 expression can increase the level of phosphorylated Rb and the transcriptional activity of E2F1, which leads to PTC cell proliferation (Li et al, 2018). Xing et al (2020) reported that in HCC cells, haprolid upregulates the expression of p21 and p27 and inhibits the G1/S phase transition of cells, which may be related to the downregulation of Rb/E2F expression. Therefore, it can be speculated that CENPN reduces the level of phosphorylated Rb and inhibits E2F1 transcription by downregulating the activities of the p27-CDK4/cyclin D1 and p21-CDK2/cyclin E axes, thus inhibiting c-myc as well as cyclin E, inhibiting cell proliferation, and ultimately affecting the prognosis of liver cancer (Fig.…”

Upregulation of CENPM facilitates tumor metastasis via the mTOR/p70S6K signaling pathway in pancreatic cancer

“…However, the specific molecular mechanisms remain unclear. Various cancer-related signaling pathways, such as JAK/STAT ( 42 ), PI3K/Akt ( 43 ), JNK ( 44 ), Wnt ( 45 ), and MAPK/ERK ( 46 ), have been revealed to play pivotal roles in tumor cell invasion and migration. The effect of CENPM in the aforementioned pathways will be explored in future studies.…”

Nanoparticle-Mediated Delivery of 2-Deoxy-D-Glucose Induces Antitumor Immunity and Cytotoxicity in Liver Tumors in Mice

“…Treatment with 2DG resulted in the suppression of total and glycolytic adenosine triphosphate (ATP) production, but not mitochondrial oxidative ATP production in the Huh7 cells ( Figure 2 A ), in agreement with no effects on the mitochondrial oxygen consumption ratio ( Figure 2 B ). Treatment with 2DG-PLGA-NPs resulted in the augmentation of AMP-activated protein kinase (AMPK) phosphorylation and the expression of endoplasmic reticulum (ER) stress-related chaperones, and the attenuation of mammalian target of rapamycin (mTOR) activity and its downstream molecules such as S6, Rb, cyclin D1, proliferating cell nuclear antigen, and vascular endothelial growth factor-A, 19 , 20 , 21 , 22 in xenograft liver tumors ( Figure 2 C ). Treatment with 2DG-PLGA-NPs decreased CD34-positive vessel density ( Figure 2 D ) and increased reactive oxygen species (ROS) production ( Figure 2 E ) in xenograft liver tumors.…”