Therapeutic targeting of BRCA1-mutated breast cancers with agents that activate DNA repair

Small-molecule activator of SMUG1 enhances repair of pyrimidine lesions in DNA

A potentially promising approach to targeted cancer prevention in genetically at-risk populations is the pharmacological upregulation of DNA repair pathways. SMUG1 is a base excision repair enzyme that ameliorates adverse genotoxic and mutagenic effects of hydrolytic and oxidative damage to pyrimidines. Here we describe the discovery and initial cellular activity of a small-molecule activator of SMUG1. Screening of a kinase inhibitor library and iterative rounds of structure-activity relationship studies produced compound 40 (SU0547), which activates SMUG1 by as much as 350 ± 60 % in vitro at 100 nM, with an AC50 of 4.3 ± 1.1 µM. To investigate the effect of compound 40 on endogenous SMUG1, we performed in vitro cell-based experiments with 5-hydroxymethyl-2'-deoxyuridine (5-hmdU), a pyrimidine oxidation product that is selectively removed by SMUG1. In several human cell lines, compound 40 at 3-5 µM significantly reduces the cytotoxicity of 5-hmdU and decreases levels of double-strand breaks induced by the damaged nucleoside. We conclude that the SMUG1 activator compound 40 is a useful tool to study the mechanisms of 5-hmdU toxicity and the potentially beneficial effects of suppressing damage to pyrimidines in cellular DNA.

Therapeutic upregulation of DNA repair pathways: strategies and small molecule activators

DNA repair activity diminishes with age and genetic mutations, leading to a significantly increased risk of cancer and other diseases. Upregulating the DNA repair system has emerged as a potential strategy to mitigate disease susceptibility while minimizing cytotoxic side effects. However, enhancing DNA repair activity presents significant challenges due to the inherent inefficiency in activator screening processes. Additionally, pinpointing a critical target that can effectively upregulate overall repair processes is complicated as the available information is somewhat sporadic. In this review, we discuss potential therapeutic targets for upregulating DNA repair pathways, along with the chemical structures and properties of reported small-molecule activators. We also elaborate on the diverse mechanisms by which these targets modulate repair activity, highlighting the critical need for a comprehensive understanding to guide the development of more effective therapeutic strategies.

Glycolysis, the sweet appetite of the tumor microenvironment

Cancer cells display an altered metabolic phenotype, characterised by increased glycolysis and lactate production, even in the presence of sufficient oxygen - a phenomenon known as the Warburg effect. This metabolic reprogramming is a crucial adaptation that enables cancer cells to meet their elevated energy and biosynthetic demands. Importantly, the tumor microenvironment plays a pivotal role in shaping and sustaining this metabolic shift in cancer cells. This review explores the intricate relationship between the tumor microenvironment and the Warburg effect, highlighting how communication within this niche regulates cancer cell metabolism and impacts tumor progression and therapeutic resistance. We discuss the potential of targeting the Warburg effect as a promising therapeutic strategy, with the aim of disrupting the metabolic advantage of cancer cells and enhancing our understanding of this complex interplay within the tumor microenvironment.

Repurposing mebendazole against triple-negative breast cancer CNS metastasis

PURPOSE

Triple-negative breast cancer (TNBC) often metastasizes to the central nervous system (CNS) and has the highest propensity among breast cancer subtypes to develop leptomeningeal disease (LMD). LMD is a spread of cancer into leptomeningeal space that speeds up the disease progression and severely aggravates the prognosis. LMD has limited treatment options. We sought to test whether the common anti-helminthic drug mebendazole (MBZ) may be effective against murine TNBC LMD.

METHODS

A small-molecule screen involving TNBC cell lines identified benzimidazoles as potential therapeutic agents for further study. In vitro migration assays were used to evaluate cell migration capacity and the effect of MBZ. For in vivo testing, CNS metastasis was introduced into BALB/c athymic nude mice through internal carotid artery injections of brain-tropic MDA-MB-231-BR or MCF7-BR cells. Tumor growth and spread was monitored by bioluminescence imaging and immunohistochemistry. MBZ was given orally at 50 and 100 mg/kg doses. MBZ bioavailability was assayed by mass spectrometry.

RESULTS

Bioinformatic analysis and migration assays revealed higher migratory capacity of TNBC compared to other breast cancer subtypes. MBZ effectively slowed down migration of TNBC cell line MDA-MB-231 and its brain tropic derivative MDA-MB-231-BR. In animal studies, MBZ reduced leptomeningeal spread, and extended survival in brain metastasis model produced by MDA-MB-231-BR cells. MBZ did not have an effect in the non-migratory MCF7-BR model.

CONCLUSIONS

We demonstrated that MBZ is a safe and effective oral agent in an animal model of TNBC CNS metastasis. Our findings are concordant with previous efforts involving MBZ and CNS pathology and support the drug's potential utility to slow down leptomeningeal spread.

Repurposing mebendazole against triple-negative breast cancer leptomeningeal disease

Purpose

Triple-negative breast cancer (TNBC) is an aggressive subtype that often metastasizes to the brain. Leptomeningeal disease (LMD), a devastating brain metastasis common in TNBC, has limited treatment options. We sought to test whether the common anti-helminthic drug mebendazole (MBZ) may be effective against murine TNBC LMD.

Methods

A small-molecule screen involving TNBC cell lines identified benzimidazoles as potential therapeutic agents for further study. In vitro migration assays were used to evaluate cell migration capacity and the effect of MBZ. For in vivo testing, LMD was introduced into BALB/c athymic nude mice through internal carotid artery injections of brain-tropic MDA-MB-231-BR or MCF7-BR cells. Tumor growth and spread was monitored by bioluminescence imaging. MBZ was given orally at 50 and 100 mg/kg doses. MBZ bioavailability was assayed by mass spectrometry.

Results

Bioinformatic analysis and migration assays revealed higher migratory capacity of TNBC compared to other breast cancer subtypes. MBZ effectively slowed down migration of TNBC cell line MDA-MB-231 and its brain tropic derivative MDA-MB-231-BR. In animal studies, MBZ reduced tumor growth and extended survival in the LMD model produced by MDA-MB-231-BR cells. MBZ did not have an effect in the non-migratory MCF7-BR model.

Conclusions

We demonstrated that MBZ is a safe and effective oral agent in an animal model of TNBC LMD. Our findings are concordant with previous efforts involving MBZ and central nervous system pathology and further support the drug's potential utility as an alternative therapeutic for TNBC LMD.

Enhancing Repair of Oxidative DNA Damage with Small-Molecule Activators of MTH1

Impaired DNA repair activity has been shown to greatly increase rates of cancer clinically. It has been hypothesized that upregulating repair activity in susceptible individuals may be a useful strategy for inhibiting tumorigenesis. Here, we report that selected tyrosine kinase (TK) inhibitors including nilotinib, employed clinically in the treatment of chronic myeloid leukemia, are activators of the repair enzyme Human MutT Homolog 1 (MTH1). MTH1 cleanses the oxidatively damaged cellular nucleotide pool by hydrolyzing the oxidized nucleotide 8-oxo-2'-deoxyguanosine (8-oxo-dG)TP, which is a highly mutagenic lesion when incorporated into DNA. Structural optimization of analogues of TK inhibitors resulted in compounds such as SU0448, which induces 1000 ± 100% activation of MTH1 at 10 μM and 410 ± 60% at 5 μM. The compounds are found to increase the activity of the endogenous enzyme, and at least one (SU0448) decreases levels of 8-oxo-dG in cellular DNA. The results suggest the possibility of using MTH1 activators to decrease the frequency of mutagenic nucleotides entering DNA, which may be a promising strategy to suppress tumorigenesis in individuals with elevated cancer risks.

BAPST. A Combo of Common use drugs as metabolic therapy of cancer-a theoretical proposal

Advances in cancer therapy have yet to impact worldwide cancer mortality. Poor cancer drug affordability is one of the factors limiting mortality burden strikes. Up to now, cancer drug repurposing had no meet expectations concerning drug affordability. The three FDA-approved cancer drugs developed under repurposing -all-trans-retinoic acid, arsenic trioxide, and thalidomide- do not differ in price from other drugs developed under the classical model. Though additional factors affect the whole process from inception to commercialization, the repurposing of widely used, commercially available, and cheap drugs may help. This work reviews the concept of the malignant metabolic phenotype and its exploitation by simultaneously blocking key metabolic processes altered in cancer. We elaborate on a combination called BAPST, which stands for the following drugs and pathways they inhibit: Benserazide (glycolysis), Apomorphine (glutaminolysis), Pantoprazole (Fatty-acid synthesis), Simvastatin (mevalonate pathway), and Trimetazidine (Fatty-acid oxidation). Their respective primary indications are: • Parkinson's disease (benserazide and apomorphine). • Peptic ulcer disease (pantoprazole). • Hypercholesterolemia (simvastatin). • Ischemic heart disease (trimetazidine). When used for their primary indication, the literature review on each of these drugs shows they have a good safety profile and lack predicted pharmacokinetic interaction among them. Most importantly, the inhibitory enzymatic concentrations required for inhibiting their cancer targets enzymes are below the plasma concentrations observed when these drugs are used for their primary indication. Based on that, we propose that the regimen BAPTS merits preclinical testing.

Metabolic changes in triple negative breast cancer-focus on aerobic glycolysis

Among breast cancer subtypes, the triple negative breast cancer (TNBC) has the worst prognosis. In absence of any permitted targeted therapy, standard chemotherapy is the mainstay for TNBC treatment. Hence, there is a crucial need to identify potential druggable targets in TNBCs for its effective treatment. In recent times, metabolic reprogramming has emerged as cancer cells hallmark, wherein cancer cells display discrete metabolic phenotypes to fuel cell progression and metastasis. Altered glycolysis is one such phenotype, in which even in oxygen abundance majority of cancer cells harvest considerable amount of energy through elevated glycolytic-flux. In the present review, we attempt to summarize the role of key glycolytic enzymes i.e. HK, Hexokinase; PFK, Phosphofructokinase; PKM2, Pyruvate kinase isozyme type 2; and LDH, Lactate dehydrogenase in TNBCs, and possible therapeutic options presently available.

High-throughput synthetic rescue for exhaustive characterization of suppressor mutations in human genes

Inherited or acquired mutations can lead to pathological outcomes. However, in a process defined as synthetic rescue, phenotypic outcome created by primary mutation is alleviated by suppressor mutations. An exhaustive characterization of these mutations in humans is extremely valuable to better comprehend why patients carrying the same detrimental mutation exhibit different pathological outcomes or different responses to treatment. Here, we first review all known suppressor mutations' mechanisms characterized by genetic screens on model species like yeast or flies. However, human suppressor mutations are scarce, despite some being discovered based on orthologue genes. Because of recent advances in high-throughput screening, developing an inventory of human suppressor mutations for pathological processes seems achievable. In addition, we review several screening methods for suppressor mutations in cultured human cells through knock-out, knock-down or random mutagenesis screens on large scale. We provide examples of studies published over the past years that opened new therapeutic avenues, particularly in oncology.

Designer Fluorescent Adenines Enable Real-Time Monitoring of MUTYH Activity

The human DNA base excision repair enzyme MUTYH (MutY homolog DNA glycosylase) excises undamaged adenine that has been misincorporated opposite the oxidatively damaged 8-oxoG, preventing transversion mutations and serving as an important defense against the deleterious effects of this damage. Mutations in the MUTYH gene predispose patients to MUTYH-associated polyposis and colorectal cancer, and MUTYH expression has been documented as a biomarker for pancreatic cancer. Measuring MUTYH activity is therefore critical for evaluating and diagnosing disease states as well as for testing this enzyme as a potential therapeutic target. However, current methods for measuring MUTYH activity rely on indirect electrophoresis and radioactivity assays, which are difficult to implement in biological and clinical settings. Herein, we synthesize and identify novel fluorescent adenine derivatives that can act as direct substrates for excision by MUTYH as well as bacterial MutY. When incorporated into synthetic DNAs, the resulting fluorescently modified adenine-release turn-on (FMART) probes report on enzymatic base excision activity in real time, both in vitro and in mammalian cells and human blood. We also employ the probes to identify several promising small-molecule modulators of MUTYH by employing FMART probes for in vitro screening.

Understanding Breast cancer: from conventional therapies to repurposed drugs

Breast cancer is the most common cancer among women and is considered a developed country disease. Moreover, is a heterogenous disease, existing different types and stages of breast cancer development, therefore, better understanding of cancer biology, helps to improve the development of therapies. The conventional treatments accessible after diagnosis, have the main goal of controlling the disease, by improving survival. In more advance stages the aim is to prolong life and symptom palliation care. Surgery, radiation therapy and chemotherapy are the main options available, which must be adapted to each person individually. However, patients are developing resistance to the conventional therapies. This resistance is due to alterations in important regulatory pathways such as PI3K/AKt/mTOR, this pathway contributes to trastuzumab resistance, a reference drug to treat breast cancer. Therefore, is proposed the repurposing of drugs, instead of developing drugs de novo, for example, to seek new medical treatments within the drugs available, to be used in breast cancer treatment. Providing safe and tolerable treatments to patients, and new insights to efficacy and efficiency of breast cancer treatments. The economic and social burden of cancer is enormous so it must be taken measures to relieve this burden and to ensure continued access to therapies to all patients. In this review we focus on how conventional therapies against breast cancer are leading to resistance, by reviewing those mechanisms and discussing the efficacy of repurposed drugs to fight breast cancer.

BRCA1/P53: Two strengths in cancer chemoprevention

Increasing emphasis has been given to prevention as a feasible approach to reduce the cancer burden. However, for its clinical success, further advances are required to identify effective chemopreventive agents. This review affords a critical and up-to-date discussion of issues related to cancer prevention, including an in-depth knowledge on BRCA1 and p53 tumor suppressor proteins as key molecular players. Indeed, it compiles the most recent advances on the topic, highlighting the unique potential of BRCA1 and p53 germline mutations as molecular biomarkers for risk assessment and targets for chemoprevention. Relevant evidences are herein provided supporting the effectiveness of distinct pharmacological agents in cancer prevention, by targeting BRCA1 and p53. Moreover, the rationale for using germline mutant BRCA1- or p53-related cancer syndromes as model systems to investigate effective chemopreventive agents is also addressed. Altogether, this work provides an innovative conception about the dependence on p53 and BRCA1 co-inactivation in tumor formation and development, emphasizing the relationship between these two proteins as an encouraging direction for future personalized pharmacological interventions in cancer prevention.

Signaling Pathways, Chemical and Biological Modulators of Nucleotide Excision Repair: The Faithful Shield against UV Genotoxicity

The continuous exposure of the human body's cells to radiation and genotoxic stresses leads to the accumulation of DNA lesions. Fortunately, our body has several effective repair mechanisms, among which is nucleotide excision repair (NER), to counteract these lesions. NER includes both global genome repair (GG-NER) and transcription-coupled repair (TC-NER). Deficiencies in the NER pathway underlie the development of several DNA repair diseases, such as xeroderma pigmentosum (XP), Cockayne syndrome (CS), and trichothiodystrophy (TTD). Deficiencies in GG-NER and TC-NER render individuals to become prone to cancer and neurological disorders, respectively. Therefore, NER regulation is of interest in fine-tuning these risks. Distinct signaling cascades including the NFE2L2 (NRF2), AHR, PI3K/AKT1, MAPK, and CSNK2A1 pathways can modulate NER function. In addition, several chemical and biological compounds have proven success in regulating NER's activity. These modulators, particularly the positive ones, could therefore provide potential treatments for genetic DNA repair-based diseases. Negative modulators, nonetheless, can help sensitize cells to killing by genotoxic chemicals. In this review, we will summarize and discuss the major upstream signaling pathways and molecules that could modulate the NER's activity.

Ginsenoside Rg1 impairs homologous recombination repair by targeting CtBP-interacting protein and sensitizes hepatoblastoma cells to DNA damage

The ginsenoside Rg1, the primary pharmacologically active ingredient of the traditional Chinese herb ginseng, is widely used in the clinical treatment of diseases of the immune and nervous systems. Recent studies have shown that it also has an antitumor effect. In this study, we explored the effects of Rg1 on hepatoblastoma (HB) and its underlying mechanisms. We demonstrated that Rg1 significantly inhibited HB cell growth both in vivo and in vitro. Mechanistic studies revealed that Rg1 impaired homologous recombination and triggered double-strand breaks in HB cells by directly targeting CtBP-interacting protein (CtIP), a key double-strand break repair factor, which is highly expressed in HB tissues. Moreover, we also demonstrated that Rg1 sensitized HB cells to DNA-damaging agents both in vitro and in vivo. In conclusion, our data not only demonstrate the potential clinical application of Rg1 as a novel chemotherapeutic candidate but also offer a mechanism-based therapeutic option by which DNA-damaging agents can be used in combination with Rg1 to target HB.

When you're strange: Unusual features of the MUTYH glycosylase and implications in cancer

MUTYH is a base-excision repair glycosylase that removes adenine opposite 8-oxoguanine (OG). Variants of MUTYH defective in functional activity lead to MUTYH-associated polyposis (MAP), which progresses to cancer with very high penetrance. Whole genome and whole exome sequencing studies have found MUTYH deficiencies in an increasing number of cancer types. While the canonical OG:A repair activity of MUTYH is well characterized and similar to bacterial MutY, here we review more recent evidence that MUTYH has activities independent of OG:A repair and appear centered on the interdomain connector (IDC) region of MUTYH. We summarize evidence that MUTYH is involved in rapid DNA damage response (DDR) signaling, including PARP activation, 9-1-1 and ATR signaling, and SIRT6 activity. MUTYH alters survival and DDR to a wide variety of DNA damaging agents in a time course that is not consistent with the formation of OG:A mispairs. Studies that suggest MUTYH inhibits the repair of alkyl-DNA damage and cyclopyrimidine dimers (CPDs) is reviewed, and evidence of a synthetic lethal interaction with mismatch repair (MMR) is summarized. Based on these studies we suggest that MUTYH has evolved from an OG:A mispair glycosylase to a multifunctional scaffold for DNA damage response signaling.

Inhibition of Glycolysis and Glutaminolysis: An Emerging Drug Discovery Approach to Combat Cancer

Cancer cells have a very different metabolism from that of normal cells from which they are derived. Their metabolism is elevated, which allows them to sustain higher proliferative rate and resist some cell death signals. This phenomenon, known as the "Warburg effect", has become the focus of intensive efforts in the discovery of new therapeutic targets and new cancer drugs. Both glycolysis and glutaminolysis pathways are enhanced in cancer cells. While glycolysis is enhanced to satisfy the increasing energy demand of cancer cells, glutaminolysis is enhanced to provide biosynthetic precursors for cancer cells. It was recently discovered that there is a tyrosine phosphorylation of a specific isoform of pyruvate kinase, the M2 isoform, that is preferentially expressed in all cancer cells, which results in the generation of pyruvate through a unique enzymatic mechanism that is uncoupled from ATP production. Pyruvate produced through this unique enzymatic mechanism is converted primarily into lactic acid, rather than acetyl-CoA for the synthesis of citrate, which would normally then enter the citric acid cycle. Inhibition of key enzymes in glycolysis and glutaminolysis pathways with small molecules has provided a novel but emerging area of cancer research and has been proven effective in slowing the proliferation of cancer cells, with several inhibitors being in clinical trials. This review paper will cover recent advances in the development of chemotherapeutic agents against several metabolic targets for cancer therapy, including glucose transporters, hexokinase, pyruvate kinase M2, glutaminase, and isocitrate dehydrogenase.

Repair of UV-Induced DNA Damage Independent of Nucleotide Excision Repair Is Masked by MUTYH

DNA lesions caused by UV damage are thought to be repaired solely by the nucleotide excision repair (NER) pathway in human cells. Patients carrying mutations within genes functioning in this pathway display a range of pathologies, including an increased susceptibility to cancer, premature aging, and neurological defects. There are currently no curative therapies available. Here we performed a high-throughput chemical screen for agents that could alleviate the cellular sensitivity of NER-deficient cells to UV-induced DNA damage. This led to the identification of the clinically approved anti-diabetic drug acetohexamide, which promoted clearance of UV-induced DNA damage without the accumulation of chromosomal aberrations, hence promoting cellular survival. Acetohexamide exerted this protective function by antagonizing expression of the DNA glycosylase, MUTYH. Together, our data reveal the existence of an NER-independent mechanism to remove UV-induced DNA damage and prevent cell death.

Benserazide, a dopadecarboxylase inhibitor, suppresses tumor growth by targeting hexokinase 2

BACKGROUND

Hexokinase (HK) is the rate-limiting enzyme in the first reaction of glycolysis. And Hexokinase 2 (HK2) is most closely related to malignant tumor which expresses at higher level compared with normal cells. HK2 plays a pivotal role in tumor initiation and maintenance, which provides a new target for cancer therapy.

METHODS

Structure-based virtual ligand screening was used in hit identification from ZINC Drug Database. Microscale thermophoresis assay was performed to evaluate the binding affinity. Enzyme inhibition, cytotoxicity, apoptosis, intracellular ATP level, mitochondrial membrane potential (MMP), glucose uptake and lactate production experiments were undertaken in SW480 cells to identify Benz as a HK2 inhibitor. Western blot was used to test protein expression. SW480 cells xenograft mouse models were used for in vivo study. Nano-particles of Benz were prepared to improve the antitumor efficacy and tumor targeting of Benz. HPLC was used to measure the concentration of free Benz in tumor tissues.

RESULTS

Benserazide (Benz), was identified as a selective HK2 inhibitor, could specifically bind to HK2 and significantly inhibit HK2 enzymatic activity in vitro. In addition, Benz reduced glucose uptake, lactate production and intracellular ATP level, and could cause cell apoptosis and an increased loss of MMP as well. In vivo study indicated that intraperitoneal (ip) injection of Benz at 300 and 600 mg/Kg suppressed cancer growth in tumor-bearing mice and no toxicity shown. To further improve the antitumor efficacy and tumor targeting of Benz, nano-particles of Benz was prepared. Liposomal Benz at 100 and 200 mg/Kg performed potent inhibitory effects on tumor-bearing mice, showing reduced dose and better efficacy.

CONCLUSIONS

Our study provides a new direction for the development of Benz and its analogues as novel antitumor agents for cancer therapy.

A Chimeric ATP-Linked Nucleotide Enables Luminescence Signaling of Damage Surveillance by MTH1, a Cancer Target

The enzyme MTH1 cleanses the cellular nucleotide pool of oxidatively damaged 8-oxo-dGTP, preventing mutagenesis by this nucleotide. The enzyme is considered a promising therapeutic target; however, methods to measure its activity are indirect and laborious and have low sensitivity. Here we describe a novel ATP-linked chimeric nucleotide (ARGO) that enables luminescence signaling of the enzymatic reaction, greatly simplifying the measurement of MTH1 activity. We show that the reporting system can be used to identify inhibitors of MTH1, and we use it to quantify enzyme activity in eight cell lines and in colorectal tumor tissue. The ARGO reporter is likely to have considerable utility in the study of the biology of MTH1 and potentially in analyzing patient samples during clinical testing.

BRCA1: a movement toward cancer prevention

Breast cancer susceptibility gene 1 (BRCA1) was first identified in 1994 and has since been shown to encode a tumor suppressor protein that maintains genetic stability through DNA damage response pathways. Carriers of mutations in BRCA1 are predisposed to breast and ovarian cancer; however, their cancers lack the targets for existing anticancer drugs. We describe a novel chemoprevention approach that uses DNA repair-activating agents to enhance the repair of oxidative DNA damage and, in turn, prevent tumorigenesis in the presence of mutant BRCA1.

Synergistic suppressive effect of PARP-1 inhibitor PJ34 and HDAC inhibitor SAHA on proliferation of liver cancer cells

Poly (ADP-ribose) polymerase-1 (PARP-1) inhibitors and histone deacetylase (HDAC) inhibitors have recently emerged as promising anticancer drugs. The aim of this study was to investigate the effect of combination treatment with the PARP inhibitor PJ34 and HDAC inhibitor SAHA on the proliferation of liver cancer cells. Cell proliferation and apoptosis were assessed in three human liver cancer cell lines (HepG2, Hep3B and HCC-LM3) treated with PJ34 (8 μmol/L) and SAHA (1 μmol/L), alone or combined, by Cell Counting Kit-8 assay and flow cytometry, respectively. The nude mice bearing subcutaneous HepG2 tumors were administered different groups of drugs (10 mg/kg PJ34, 25 mg/kg SAHA, 10 mg/kg PJ34+25 mg/kg SAHA), and the inhibition rates of tumor growth were compared between groups. The results showed that combined use of PJ34 and SAHA could synergistically inhibit the proliferation of liver cancer cell lines HepG2, Hep3B and HCC-LM3. The apoptosis rate of HepG2 cells treated with PJ34+SAHA was significantly higher than that of HepG2 cells treated with PJ34 or SAHA alone (P<0.05). In vivo, the tumor inhibition rates were 53.5%, 61.4% and 82.6% in PJ34, SAHA and PJ34+SAHA groups, respectively. The combined use of PJ34 and SAHA could significantly inhibit the xenograft tumor growth when compared with use of PJ34 or SAHA alone (P<0.05). It was led to conclude that PJ34 and SAHA can synergistically suppress the proliferation of liver cancer cells.