Genes Regulating the Sensitivity of Solid Tumor Cell Lines to Cytotoxic Agents: A Literature Review

Inhibitors of DNA Methylation and Histone Deacetylation as Epigenetically Active Drugs for Anticancer Therapy

Gene expression is regulated and tightly controlled by epigenetic mechanisms. Alterations of these mechanisms are frequently observed in various diseases, particularly, in various types of cancer. Malignant transformation is caused by the impairment of the mechanisms of cell differentiation and cell cycle control associated with epigenetic changes. Altered patterns of epigenetic modification associated with malignancies can potentially be reversed by some agents that act on the key proteins responsible for DNA/histone modification and chromatin remodelling. Examples of such substances include the inhibitors of DNA methyltransferases or histone deacetylase. During the recent years, a number of such substances have been evaluated as potential therapeutic agents against certain types of cancer in preclinical and clinical studies, and some of them have been approved for treatment of hematological cancers. Application of epidrugs for therapy of solid tumors remains, however, more challenging. In this review, we summarize the current knowledge on the most studied mechanisms of epigenetic modification and the available epigenetically active drugs.

Anthocyanins from roselle extract arrest cell cycle G2/M phase transition via ATM/Chk pathway in p53-deficient leukemia HL-60 cells

Cell cycle regulation is an important issue in cancer therapy. Delphinidin and cyanidin are two major anthocyanins of the roselle plant (Hibiscus sabdariffa). In the present study, we investigated the effect of Hibiscus anthocyanins (HAs) on cell cycle arrest in human leukemia cell line HL-60 and the analyzed the underlying molecular mechanisms. HAs extracted from roselle calyces (purity 90%) markedly induced G2/M arrest evaluated with flow cytometry analysis. Western blot analyses revealed that HAs (0.1-0.7 mg mL^-1 ) induced G2/M arrest via increasing Tyr15 phosphorylation of Cdc2, and inducing Cdk inhibitors p27 and p21. HAs also induced phosphorylation of upstream signals related to G2/M arrest such as phosphorylation of Cdc25C tyrosine phosphatase at Ser216, increasing the binding of pCdc25C with 14-3-3 protein. HAs-induced phosphorylation of Cdc25C could be activated by ATM checkpoint kinases, Chk1, and Chk2. We first time confirmed that ATM-Chk1/2-Cdc25C pathway as a critical mechanism for G2/M arrest in HAs-induced leukemia cell cycle arrest, indicating that this compound could be a promising anticancer candidate or chemopreventive agents for further investigation. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1290-1304, 2017.

Adenovirus-mediated LRIG1 expression enhances the chemosensitivity of bladder cancer cells to cisplatin

Cisplatin (cis-diaminodichloroplatinum, CDDP) is one of the most effective chemotherapeutic agents that has been widely used in the treatment of many malignancies, including muscle invasive bladder cancer. However, development of CDDP resistance in cancer cells is a major obstacle to the effective treatment of bladder cancer. Therefore, the development of chemosensitizers to overcome the acquired resistance to chemotherapeutic agents is crucial. Previous studies have confirmed that the epidermal growth factor receptor (EGFR) and its signaling pathways are important in the chemoresistance of cancer cells against CDDP‑induced cell apoptosis. In a preliminary study we showed that leucine-rich repeats and immunoglobulin-like domains 1 (LRIG1) is the natural ligand of EGFR, and that the extracellular leucine-rich repeat (LRR) domain and immunoglobulin-like domains of LRIG1 were able to bind to the extracellular domain of EGFR, resulting in the downregulation of EGFR expression. Based on these findings, we hypothesized that LRIG1 may enhance the chemosensitivity of bladder cancer cells to CDDP. In the present study, LRIG1 was overexpressed by the adenovirus vector to determine the effect of LRIG1 on chemosensitivity in the T24 bladder cancer cell line and explored the possible mechanisms. The results showed that CDDP inhibited the growth of the T24 cell line and induced activation of EGFR. Overexpression of LRIG1 increased the inhibitory effect of CDDP on the T24 cell line, which may be associated with inactivation of the EGFR signaling pathway, followed by the decrease of Bcl-2 expression and a concomitantly induced expression of Bax. Based on these results, we concluded that the upregulation of LRIG1 expression inhibited the EGFR signaling pathway, activated the mitochondrial pathway of apoptosis and eventually increased the sensitivity of bladder cancer cells to CDDP.

Prediction of individual response to anticancer therapy: historical and future perspectives

Since the introduction of chemotherapy for cancer treatment in the early 20th century considerable efforts have been made to maximize drug efficiency and at the same time minimize side effects. As there is a great interpatient variability in response to chemotherapy, the development of predictive biomarkers is an ambitious aim for the rapidly growing research area of personalized molecular medicine. The individual prediction of response will improve treatment and thus increase survival and life quality of patients. In the past, cell cultures were used as in vitro models to predict in vivo response to chemotherapy. Several in vitro chemosensitivity assays served as tools to measure miscellaneous endpoints such as DNA damage, apoptosis and cytotoxicity or growth inhibition. Twenty years ago, the development of high-throughput technologies, e.g. cDNA microarrays enabled a more detailed analysis of drug responses. Thousands of genes were screened and expression levels were correlated to drug responses. In addition, mutation analysis became more and more important for the prediction of therapeutic success. Today, as research enters the area of -omics technologies, identification of signaling pathways is a tool to understand molecular mechanism underlying drug resistance. Combining new tissue models, e.g. 3D organoid cultures with modern technologies for biomarker discovery will offer new opportunities to identify new drug targets and in parallel predict individual responses to anticancer therapy. In this review, we present different currently used chemosensitivity assays including 2D and 3D cell culture models and several -omics approaches for the discovery of predictive biomarkers. Furthermore, we discuss the potential of these assays and biomarkers to predict the clinical outcome of individual patients and future perspectives.

5-(2-carboxyethenyl) isatin derivative induces G₂/M cell cycle arrest and apoptosis in human leukemia K562 cells

Our previous study successfully identified that the novel isatin derivative (E)-methyl 3-(1-(4-methoxybenzyl)-2,3-dioxoindolin-5-yl) acrylate (HKL 2H) acts as an anticancer agent at an inhibitory concentration (IC50) level of 3nM. In this study, the molecular mechanism how HKL 2H induces cytotoxic activity in the human chronic myelogenous leukemia K562 cells was investigated. Flow cytometric analysis showed that the cells were arrested in the G2/M phase and accumulated subsequently in the sub-G1 phase in the presence of HKL 2H. HKL 2H treatment down-regulated the expressions of CDK1 and cyclin B but up-regulated the level of phosphorylated CDK1. Annexin-V staining and the classic DNA ladder studies showed that HKL 2H induced the apoptosis of K562 cells. Our study further showed that HKL 2H treatment caused the dissipation of mitochondrial membrane potential, activated caspase-3 and lowered the Bcl-2/Bax ratio in K562 cells, suggesting that the HKL 2H-causing programmed cell death of K562 cells was caused via the mitochondrial apoptotic pathway. Taken together, our data demonstrated that HKL 2H, a 5-(2-carboxyethenyl) isatin derivative, notably induces G2/M cell cycle arrest and mitochondrial-mediated apoptosis in K562 cells, indicating that this compound could be a promising anticancer candidate for further investigation.

Using the theory of coevolution to predict protein-protein interactions in non-small cell lung cancer

Systems biology has become an effective approach for understanding the molecular mechanisms underlying the development of lung cancer. In this study, sequences of 100 non-small cell lung cancer (NSCLC)-related proteins were downloaded from the National Center for Biotechnology Information (NCBI) databases. The Theory of Coevolution was then used to build a protein-protein interaction (PPI) network of NSCLC. Adopting the reverse thinking approach, we analyzed the NSCLC proteins one at a time. Fifteen key proteins were identified and categorized into a special protein family F (K), which included Cyclin D1 (CCND1), E-cadherin (CDH1), Cyclin-dependent kinase inhibitor 2A (CDKN2A), chemokine (C-X-C motif) ligand 12 (CXCL12), epidermal growth factor (EGF), epidermal growth factor receptor (EGFR), TNF receptor superfamily, member 6 (FAS), FK506 binding protein 12-rapamycin associated protein 1 (FRAP1), O-6-methylguanine-DNA methyltransferase (MGMT), parkinson protein 2, E3 Ubiquitin protein ligase (PARK2), phosphatase and tensin homolog (PTEN), calcium channel voltage-dependent alpha 2/delta subunit 2 (CACNA2D2), tubulin beta class I (TUBB), SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily a, member 2 (SMARCA2), and wingless-type MMTV integration site family, member 7A (WNT7A). Seven key nodes of the sub-network were identified, which included PARK2, WNT7A, SMARCA2, FRAP1, CDKN2A, CCND1, and EGFR. The PPI predictions of EGFR-EGF, PARK2-FAS, PTEN-FAS, and CACNA2D2-CDH1 were confirmed experimentally by retrieving the Biological General Repository for Interaction Datasets (BioGRID) and PubMed databases. We proposed that the 7 proteins could serve as potential diagnostic molecular markers for NSCLC. In accordance with the developmental mode of lung cancer established by Sekine et al., we assumed that the occurrence and development of lung cancer were linked not only to gene loss in the 3p region (WNT7A, 3p25) and genetic mutations in the 9p region but also to similar events in the regions of 1p36.2 (FRAP1), 6q25.2-q27 (PARK2), and 11q13 (CCND1). Lastly, the invasion or metastasis of lung cancer happened.

Hepatocellular carcinoma HepG2 cell apoptosis and caspase-8 and Bcl-2 expression induced by injectable seed extract of Coix lacryma-jobi

BACKGROUND

Many Chinese herbs, especially herbal injections, have been shown to have anti-tumor effects in recent years. However, since most reports focus on the clinical effectiveness of these herbs, their mechanisms of action are not well understood. In this study, we assessed apoptosis in the hepatocellular carcinoma (HCC) cell line HepG2 induced by an injectable extract from the seed of Coix lacryma-jobi (Semen coicis, SC), and monitored the expression of Bcl-2 and caspase-8.

METHODS

Injectable SC was applied to HepG2 cells at different concentrations and the cells were collected 12, 24 and 48 hours later. 5-fluorouracil was used as a positive control group, and fluorescence-activated cell-sorting cytometry was used to measure the apoptosis rate of HepG2 cells and the expression of Bcl-2 and caspase-8 proteins.

RESULTS

SC induced apoptosis in HepG2 cells in a concentration- and time-dependent manner, and the expression of caspase-8 was elevated and prolonged. However, it did not significantly influence the expression of Bcl-2.

CONCLUSION

Injectable SC may induce apoptosis in HCC cells by regulating the expression of caspase-8.

Anticancer activity and mode of action of titanocene C

Titanocenes constitute a class of metal-based anticancer agents that seem to display a mode of action distinct from that of platinum complexes and to be more tolerable with a differing spectrum of activity. In the present study, titanocene C (bis-(N,N-dimethylamino-2(N-methylpyrrolyl)-methyl-cyclopentadienyl) titanium(IV) dichloride) was shown to exhibit antiproliferative activity against human tumor cell lines with a mean IC₅₀ value of 48.3 ± 32.5 µM. In particular, high activity was found against small cell lung cancer (SCLC) cell lines with a profile different from cisplatin. Titanocene C induced cell cycle arrest at the G1/0-S interphase. Cross-resistance to either cisplatin or oxoplatin, respectively, was low for titanocene C and absent for titanocene Y in variant HL-60 cell lines. Alterations in gene expression of NCI-H526 SCLC cells induced by titanocene C were investigated using genome-wide expression arrays. Downregulation was found for genes coding for topoisomerases I and IIα, histones of the HIST1H4 cluster, enzymes involved in glycolysis, components of the cytoskeleton and vesicular transport, among others. In contrast, expression of genes involved in apoptosis, stress response, particularly members of the metallothionein gene cluster 1, DNA damage and growth factors was upregulated following exposure to titanocene C. Approximately 50% of those genes downregulated by titanocene C and cisplatin were concordant, including the previously identified markers of cisplatin-sensitivity, tubulin and stathmin, indicating partial overlap of the pathways affected by these metal complexes. The present findings point helicases/topoisomerases and HIST1H4 core histones out as targets of titanocene C and metallothioneins as putative main effectors of drug resistance.

A literature review of molecular markers predictive of clinical response to cytotoxic chemotherapy in patients with breast cancer

BACKGROUND

We aimed to identify, through a review of the literature, candidate genes for a prospective predictive chemosensitivity test in patients with breast cancer.

METHODS

Papers demonstrating an association between gene alterations in tumor tissue and clinical chemosensitivity in breast cancer patients were selected by Medline searches. We calculated odds ratios (ORs) and their 95% confidence intervals (CIs) of response rates for patients who had tumors with or without gene alteration. Combined ORs and CIs were estimated using the DerSimonian-Laird method.

RESULTS

A total of 18 genes were evaluated for association with clinical chemosensitivity in 6378 patients registered in 69 studies. The median (range) number of patients in each study was 73 (29-319). Overexpression of ABCB1 (P-glycoprotein) was associated with poor responses to first-line chemotherapy (combined OR [CI], 0.16 [0.05-0.59]; n = 322). Overexpression and amplification of TOP2A (topoisomerase II-alfa) were more frequently observed in patients who responded to first-line chemotherapy (combined OR [CI], 2.73 [1.02-7.27]; n = 323). Overexpression of ERBB2 (c-erbB2) was associated with favorable responses in patients treated with both first-line anthracycline-based chemotherapy and second-line taxane-based chemotherapy (combined ORs [CIs], 1.60 [1.19-2.17]; n = 1807 and 2.24 [1.06-4.74]; n = 259, respectively). BCL2 overexpression was associated with resistance to first-line chemotherapy (combined OR [CI], 0.44 [0.21-0.91]; n = 816).

CONCLUSION

ABCB1, TOP2A, ERBB2, and BCL2 were good candidates for future clinical trials of predictive chemosensitivity tests in patients with breast cancer.