Regulators of apoptosis as anticancer targets

Thiazole in the targeted anticancer drug discovery

Cancer is known as one of the main causes of death in the world; and many compounds have been synthesized to date with potential use in cancer therapy. Thiazole is a versatile heterocycle, found in the structure of many drugs in use as well as anticancer agents. This review provides an overview of recent advances in thiazole-bearing compounds as anticancer agents with particular emphasis on their mechanism of action in cancerous cells. Chemical designs, structure–activity relationships and relevant preclinical properties have been comprehensively described.

Clinical benefit for patients with non-small cell lung cancer enrolled in phase I trials

AIM

To analyze the clinical features and outcomes of advanced non-small cell lung cancer (NSCLC) patients treated in phase I trials.

PATIENTS AND METHODS

The clinical characteristics, efficacy and toxicity data of 70 pretreated NSCLC patients enrolled in 17 phase I trials between January 2005 and June 2010 were analyzed at our institution.

RESULTS

The histological types were: adenocarcinoma (79%), squamous cell carcinoma (13%), and others. Patients received a median number of 3 prior lines of treatment before inclusion. 1 complete response (CR), 11 (16%) partial responses (PRs), and 29 (41%) stable diseases (SDs) were observed (according to Response Evaluation Criteria in Solid Tumors (RECIST)). The median overall survival (OS) time was 18 months and the median progression-free survival (PFS) time was 4.1 months. The median PFS of these patients within their prior therapy line before phase I inclusion was 4.3 months. A performance status score of 0 and the number of prior lines of treatment were significant for OS and PFS in multivariate analysis, respectively. Grade 3/4 toxicities were observed in 20 (27%) patients, and there was 1 treatment-related death.

CONCLUSION

Patients in good general condition and with limited pretreatment derived an improved benefit, suggesting that phase I studies may be a valid option for pretreated NSCLC patients.

Halogenated flavanones as potential apoptosis-inducing agents: synthesis and biological activity evaluation

A series of halogenated flavanones were synthesized from 2-hydroxychalcones and tested for their cytotoxicity against a panel of human cancer cell lines. Among the synthesized compounds, 3',7-dichloroflavanone (2d) showed the highest activity against MCF-7, LNCaP, PC3, Hep-G2, KB and SK-N-MC cells. However, 3',6-dichloroflavanone (2g) with IC(50) value of 2.9 ± 0.9 μM was the most potent compound against MDA-MB-231 cells, being approximately 12 times more active than etoposide as reference drug. According to the flow-cytometric analysis, compound 2g can induce apoptosis by 66.19 and 21.37% in PC3 and MDA-MB-231 cells, respectively. The results of acridine orange/ethidium bromide staining and TUNEL assay suggested that the cytotoxic activity of this compound in PC3 and MDA-MB-231 cells occurs via apoptosis.

Is there any correlation between TNF-related apoptosis-inducing ligand (TRAIL) genetic variants and breast cancer?

INTRODUCTION

TNF-related apoptosis-inducing ligand (TRAIL) is a death ligand and also a member of the TNF superfamily. We aimed to investigate the possible relationship between TRAIL and breast cancer. Here, we report the results of the first association study on genetic variation in the TRAIL gene and its effect on breast cancer susceptibility and prognosis.

MATERIAL AND METHODS

A C/T polymorphism at 1595 position in exon 5 of the TRAIL gene was genotyped in a Turkish breast cancer case-control population including 53 cases (mean age: 55.09 ±11.63 years) and 57 controls (mean age: 57.17 ±17.48 years) using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis.

RESULTS

There were no differences in the distribution of TRAIL genotypes and frequencies of the alleles in the breast cancer patients and controls. A heterozygous TRAIL CT polymorphism in exon 5 was present in 8.3% of tumour stage III-IV and 48.8% of stage I-II patients, and in 42.1% of controls. The reduced frequency of this genotype in patients who had advanced tumour stage was statistically significant (p = 0.017).

CONCLUSIONS

Our findings indicate that genetic variants of TRAIL at position 1595 in exon 5 might be associated with progression of breast cancer.

A novel vicious cycle cascade in tumor chemotherapy

Dendritic cells (DCs) play a critical role in both the cellular and humoral immune response to tumor cells. The participation of co-stimulator molecules on DCs is of vital importance for full activation of T cells. Conventional tumor chemotherapy cannot only induce apoptosis of malignant cells, but also do harm to benign DCs. Expression levels of co-stimulatory molecules (especially CD80 and CD86) are downregulated during anticancer drug treatment. These DCs are defective in their antigen-presenting function being lack of sufficient co-stimulatory molecules. Immune defective DCs provide negative immune signals to CD4+ and CD8+ T cells. Thereby these T cells are induced to become tolerant to the tumor cells, and function as T regulatory/suppressor cells to induce tolerogenic DCs by cell-cell contact. These DCs tolerized to tumor antigens may further render tolerogenicity to many more T cells via intercellular contact, and thus lead to a vicious cycle cascade. This model allowed us to envisage modified strategies of antitumor chemotherapy. We may use anticancer drugs with higher specificity to tumor cells, or in combination with immunopotentiator to disrupt the vicious cycle cascade, and expect better clinical result.

Structurally related antitumor effects of flavanones in vitro and in vivo: involvement of caspase 3 activation, p21 gene expression, and reactive oxygen species production

Flavonoids exist extensively in plants and Chinese herbs, and several biological effects of flavonoids have been demonstrated. The antitumor effects in colorectal carcinoma cells (HT29, COLO205, and COLO320HSR) of eight flavanones including flavanone, 2'-OH flavanone, 4'-OH flavanone, 6-OH flavanone, 7-OH flavanone, naringenin, nargin, and taxifolin were investigated. Results of the MTT assay indicate that 2'-OH flavanone showed the most potent cytotoxic effect on these three cells, and cell death induced by 2'-OH flavanone was via the occurrence of DNA ladders, apoptotic bodies, and hypodiploid cells, all characteristics of apoptosis. Induction of caspase 3 protein processing and enzyme activity associated with cleavage of poly(ADP-ribose) polymerase (PARP) was identified in 2'-OH flavanone-treated cells, and a peptidyl inhibitor (Ac-DEVD-FMK) of caspase 3 attenuated the cytotoxicity of 2'-OH flavanone in COLO205 and HT-29 cells. Elevation of p21 (but not p53) and a decrease in Mcl-1 protein were found in 2'-OH flavanone-treated COLO205 and HT-29 cells. Elevation of intracellular reactive oxygen species (ROS) was detected in 2'-OH flavanone-treated cells by the 2',7'-dichlorodihydrofluorescein diacetate (DCHF-DA) assay, and ROS scavengers including 4,5-dihydro-1,3-benzene disulfonic acid (tiron), catalase, superoxide dismutase (SOD), and pyrrolidine dithiocarbamate (PDTC) suppressed the 2'-OH flavanone-induced cytotoxic effect. Subcutaneous injection of COLO205 induced tumor formation in nude mice, and 2'-OH flavanone showed a significant inhibitory effect on tumor formation. The appearance of apoptotic cells with H&E staining, and an increase in p21, but not p53, protein by immunohistochemistry were observed in tumor tissues under 2'-OH flavanone treatment. Primary tumor cells (COLO205-X) derived from a tumor specimen elicited by COLO205 were established, and 2'-OH flavanone showed an significant apoptotic effect in COLO205-X cells in accordance with the appearance of DNA ladders, caspase 3 protein processing, PARP protein cleavage, and increasing p21 protein. These results revealed in vitro, ex vivo, and in vivo antitumor activities of 2'-OH flavanone via apoptosis induction, and indicates that 2'-OH flavanone is an active compound worthy of development for cancer chemotherapy.