Suberoylanilide hydroxamic acid enhances chemosensitivity to 5-fluorouracil in hepatocellular carcinoma via inhibition of thymidylate synthase

The evaluation of the efficacy and potential genotoxic hazard of combined SAHA and 5-FU treatment in the chemoresistant colorectal cancer cell lines

5-Fluorouracil (5-FU) is an essential chemotherapeutic drug for colorectal cancer (CRC) treatment. However, the frequent development of drug resistance has dramatically affected its clinical use. Therefore, novel treatment strategies are critical to improving patient outcomes. Herein, we investigated the ability of the epigenetic drug SAHA to increase the sensitivity of chemoresistant CRC cells to 5-FU. In addition, we evaluated the potential genotoxic risk of SAHA+5-FU combination treatment. As a model system, we used three CRC cell lines, HT-29, SW480, and HT-29/EGFP/FUR, differing in their resistance to 5-FU. CRC cell lines were exposed to sub-toxic SAHA concentrations for 24 h, followed by a 48 h treatment with 5-FU. The cytotoxicity of SAHA, 5-FU, and SAHA+5-FU was measured by the MTT test, the genotoxicity by the comet assay, and the micronucleus test. The apoptotic/necrotic activity was assessed using morphological criteria. We found a synergic decrease in the viability of HT-29 and SW480 cells, but not the most resistant HT-29/EGFP/FUR cells after combined SAHA+5-FU exposure compared to 5-FU. Remarkably, SAHA most efficiently induced apoptosis in HT-29/EGFP/FUR cells compared to HT-29 and SW480 cells. Combined SAHA+5-FU treatment resulted in a synergistic increase in apoptotic/necrotic cells in HT-29 cell line, while rather additive/sub-additive effect was determined in the SW480 and HT-29/EGFP/FUR cells. At the same time, however, a synergistic rise in micronuclei was found in CRC cell lines (at least at some concentrations). We have shown that SAHA can sensitize CRC cells to 5-FU; therefore, epigenetic and convential drug combinations could be beneficial for the patients. However, the increase in micronucleus formation after combined SAHA+5-FU treatment indicates a potential health hazard. The clastogenic activity could contribute to cancer heterogeneity, favoring progeny of such aberrant cells to clonal expansion. Therefore, developing new specific epigenetic drugs or nanocarriers for targeted drug delivery might reduce the potential genotoxic risk.

Upregulation of histone acetylation reverses organic anion transporter 2 repression and enhances 5-fluorouracil sensitivity in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors in the world. The failure of chemotherapy in HCC patients is partly due to inadequate intracellular drug accumulation caused by abnormally expressed drug transporters. Human organic anion transporter 2 (hOAT2), a transporter mainly expressed in liver and kidney, is responsible for uptake of various antineoplastic drugs such as 5-fluorouracil (5-FU). Among 32 pairs of human HCC samples, we preliminarily found that OAT2 was suppressed in HCC tissues compared with matched tumor-adjacent tissues at both mRNA and protein levels, which resulted in 5-FU resistance in HCC. However, the epigenetic regulatory mechanisms of OAT2 downregulation have not been investigated. In this study, we first proved it was histone hypoacetylation rather than DNA hypermethylation that participated in transcriptional repression of OAT2 in two HCC cell lines (BEL-7402 and SMMC-7721). In general, there were two pathways confirmed using tissues and cells: 1) Increased histone deacetylase sirtuin 7 (SIRT7) mediated loss of histone 3 lysine 18 acetylation (H3K18ac) at the promoter of OAT2 and inhibited its transcription. 2) More histone deacetylase 7 (HDAC7) instead of lysine acetyltransferase 8 (KAT8) enrichment at the promoter of OAT2 led to low levels of histone 4 lysine 16 acetylation (H4K16ac). Further, we found that histone deacetylases inhibitor vorinostat (SAHA) could reverse histone hypoacetylation state to activate OAT2 transcription and enhance uptake of classic OAT2 substrate zidovudine. Therefore, we evaluated the effect of combining SAHA and 5-FU and the results demonstrated that SAHA could sensitize HCC cells to 5-FU. Collectively, we proposed such a combination treatment to overcome 5-FU resistance in HCC from the perspective of epigenetically restoring OAT2.

ING5-mediated antineuroblastoma effects of suberoylanilide hydroxamic acid

Neuroblastoma is the most common extracranial solid neuroendocrine cancer and is one of the leading causes of death in children. To improve clinical outcomes and prognosis, discovering new promising drugs and targeted medicine is essential. We found that applying Suberoylanilide hydroxamic acid (SAHA; Vorinostat, a histone deacetylase inhibitor) and MG132 (a proteasome inhibitor) to SH‐SY5Y cells synergistically suppressed proliferation, glucose metabolism, migration, and invasion and induced apoptosis and cell cycle arrest. These effects occurred both concentration and time dependently and were associated with the effects observed with inhibitor of growth 5 (ING5) overexpression. SAHA and MG132 treatment increased the expression levels of ING5, PTEN, p53, Caspase‐3, Bax, p21, and p27 but decreased the expression levels of 14‐3‐3, MMP‐2, MMP‐9, ADFP, Nanog, c‐myc, CyclinD1, CyclinB1, and Cdc25c concentration dependently, similar to ING5. SAHA may downregulate miR‐543 and miR‐196‐b expression to enhance the translation of ING5 protein, which promotes acetylation of histones H3 and H4. All three proteins (ING5 and acetylated histones H3 and H4) were recruited to the promoters of c‐myc, Nanog, CyclinD1, p21, and p27 for complex formation, thereby regulating the mRNA expression of downstream genes. ING5 overexpression and SAHA and/or MG132 administration inhibited tumor growth in SH‐SY5Y cells by suppressing proliferation and inducing apoptosis. The expression of acetylated histones H3 and ING5 may be closely linked to the tumor size of neuroblastomas. In summary, SAHA and/or MG132 can synergistically suppress the malignant phenotypes of neuroblastoma cells through the miRNA‐ING5‐histone acetylation axis and via proteasomal degradation, respectively. Therefore, the two drugs may serve as potential treatments for neuroblastoma.

SAHA and/or MG132 reverse the aggressive phenotypes of glioma cells: An in vitro and vivo study

To elucidate the anti-tumor effects and molecular mechanisms of SAHA (a histone deacetylase inhibitor) and MG132 (a proteasome inhibitor) on the aggressive phenotypes of glioma cells, we treated U87 and U251 cells with SAHA or/and MG132, and detected phenotypes’ assays with phenotype-related molecules examined. It was found that SAHA or/and MG132 treatment suppressed proliferation in both concentration- and time-dependent manners, inhibited energy metabolism, migration, invasion and lamellipodia formation, and induced G₂ arrest and apoptosis in the glioma cells. The treatment with SAHA increased the expression of acetyl-histones 3 and 4, which were recruited to the promoters of p21, p27, Cyclin D1, c-myc and Nanog to down-regulate their transcriptional levels. Expression of acetyl-histones 3 and 4 was higher in gliomas than normal brain tissues. Both drugs’ exposure suppressed tumor growth in nude mice by inducing apoptosis and inhibiting proliferation, but increased serum aminotransferase and creatinine. These results indicated that SAHA and/or MG132 may suppress the aggressive phenotypes of glioma cells. They might be employed to treat the glioma if both hepatic and renal injuries are prevented.

Evodiamine induces apoptosis and promotes hepatocellular carcinoma cell death induced by vorinostat via downregulating HIF-1α under hypoxia

Hypoxia promotes HCC progression and therapy resistance, and there is no systemic treatment for HCC patients after sorafenib resistance. Thus, it is urgent to develop potential therapeutic regimens for HCC patients by targeting hypoxia signaling. In this study, we showed that evodiamine might be a potential therapeutic medicine for HCC by suppressing HIF-1α. In addition, evodiamine could sensitize the anti-HCC effect of vorinostat in HCC cells under hypoxia. Furthermore, evodiamine plus vorinostat accelerated the degradation of HIF-1α in HCC cells under hypoxia. In general, evodiamine might be a potential therapeutic candidate for HCC patients, and evodiamine combining with vorinostat might be an attractive chemotherapy strategy for HCC treatment.

Regulation of ERK and AKT pathways by hepatitis B virus X protein via the Notch1 pathway in hepatocellular carcinoma

Hepatitis B virus (HBV) is the dominant risk factor for hepatocellular carcinoma (HCC). HBV X protein (HBx) plays crucial roles in HCC carcinogenesis. HBx interferes with several signaling pathways including the Notch1 pathway in HCC. In this study, we found that Notch1 was highly expressed in HCC, especially in large HCCs. Notch1 and HBx co-localized in HCC and their levels were positively correlated with each other. Notch1 expression was more elevated in HepG2.2.15 cells than that in HepG2 cells. HBx activated the Notch1 pathway in HepG2.2.15 cells. Suppression of HBx and the Notch1 pathway attenuated the growth of HepG2.2.15 cells. Notch1, ERK, and AKT pathways were inhibited after γ-secretase inhibitor treatment. Dual-specificity phosphatase 1 (DUSP1) and phosphatase and tensin homolog (PTEN) were upregulated after γ-secretase inhibitor treatment and Hes1 inhibition. Luciferase reporter assays showed that Hes1 suppressed the promoters of DUSP1 and PTEN genes, which was reversed by γ-secretase inhibitor treatment. Western blotting demonstrated that DUSP1 dephosphorylated pERK and PTEN dephosphorylated pAKT. Collectively, we found a link among HBx, the Notch1 pathway, DUSP1/PTEN, and ERK/AKT pathways, which influenced HCC cell survival and could be a therapeutic target for HCC treatment.

Raltitrexed Inhibits HepG2 Cell Proliferation via G0/G1 Cell Cycle Arrest

Raltitrexed (RTX) is an antimetabolite drug used as a chemotherapeutic agent for treating colorectal cancer, malignant mesothelioma, and gastric cancer. The antitumor capacity of RTX is attributed to its inhibitory activity on thymidylate synthase (TS), a key enzyme in the synthesis of DNA precursors. The current study is aimed at investigating the potential antitumor effects of RTX in liver cancer. Using the HepG2 cell line as an in vitro model of liver cancer, we evaluated the effects of RTX on cell proliferation employing both a WST-8 assay and a clone formation efficiency assay. In addition, we monitored the ultrastructure changes of HepG2 cells in response to RTX with transmission electric microscopy. To investigate the mechanism underlying the regulation of cell proliferation by RTX, we analyzed cell cycle using cell flow cytometry. Moreover, real-time PCR and Western blot analyses were conducted to examine expression levels of cell cycle regulatory proteins cyclin A and cyclin-dependent kinase 2 (CDK2), as well as their mediators tumor suppressor genes p53 and p16. Our results demonstrate that RTX inhibits HepG2 proliferation by arresting the cell cycle at G₀/G₁. This cell cycle arrest function was mediated via downregulation of cyclin A and CDK2. The observed elevated expression of p53 and p16 by RTX may contribute to the reduction of cyclin A/CDK2. Our study indicates that RTX could serve as a potential chemotherapeutic agent in the treatment of hepatocellular carcinoma.

pH-Sensitive mesoporous silica nanoparticles anticancer prodrugs for sustained release of ursolic acid and the enhanced anti-cancer efficacy for hepatocellular carcinoma cancer

Ursolic acid (UA) as a nature product exhibits good anti-cancer activity, low toxicity, and good liver protection features. However, the low-solubility and poor bioavailability restrict its further clinical application. To overcome this problem, a pH-sensitive prodrug delivery system (UA@MSN-UA) that incorporated acid-sensitive linkage between drug and silica-based mesoporous nanosphere (MSN) was successfully designed and synthesized. The physicochemical properties of the UA@MSN-UA nanoparticles were investigated for shape, particle size, zeta potential, nitrogen adsorption-desorption and infrared (IR) spectroscopy. The nanoparticles were further evaluated for in vitro cytotoxicity, including proliferation inhibition, cell cycle distribution and apoptotic effects against human hepatocellular carcinoma HepG2 cells. The TEM image showed that the size of synthesized MSN nanoparticle was a near-spherical shape with ~100nm diameter. In vitro cytotoxicity testing demonstrated that UA@MSN-UA nanoparticles prodrug exhibited higher proliferation inhibition, cell cycle arrest at the G2/M phase and significantly caused the early and late apoptosis in HepG2 cells, which would be contributed to high loading capacity, high cellular uptake and sustained release of UA. Overall, the UA-modified MSN prodrug delivery system can be a promising drug carrier for improving the bioavailability of UA, and further enhance its anti-cancer efficacy.