Discovery of a first-in-class reversible DNMT1-selective inhibitor with improved tolerability and efficacy in acute myeloid leukemia.

DNA methylation, a key epigenetic driver of transcriptional silencing, is universally dysregulated in cancer. Reversal of DNA methylation by hypomethylating agents, such as the cytidine analogs decitabine or azacytidine, has demonstrated clinical benefit in hematologic malignancies. These nucleoside analogs are incorporated into replicating DNA where they inhibit DNA cytosine methyltransferases DNMT1, DNMT3A and DNMT3B through irreversible covalent interactions. These agents induce notable toxicity to normal blood cells thus limiting their clinical doses. Herein we report the discovery of GSK3685032, a potent first-in-class DNMT1-selective inhibitor that was shown via crystallographic studies to compete with the active-site loop of DNMT1 for penetration into hemi-methylated DNA between two CpG base pairs. GSK3685032 induces robust loss of DNA methylation, transcriptional activation and cancer cell growth inhibition in vitro. Due to improved in vivo tolerability compared with decitabine, GSK3685032 yields superior tumor regression and survival mouse models of acute myeloid leukemia.

Mode of action of DNA-competitive small molecule inhibitors of tyrosyl DNA phosphodiesterase 2.

Tyrosyl-DNA phosphodiesterase 2 (TDP2) is a 5'-tyrosyl DNA phosphodiesterase important for the repair of DNA adducts generated by non-productive (abortive) activity of topoisomerase II (TOP2). TDP2 facilitates therapeutic resistance to topoisomerase poisons, which are widely used in the treatment of a range of cancer types. Consequently, TDP2 is an interesting target for the development of small molecule inhibitors that could restore sensitivity to topoisomerase-directed therapies. Previous studies identified a class of deazaflavin-based molecules that showed inhibitory activity against TDP2 at therapeutically useful concentrations, but their mode of action was uncertain. We have confirmed that the deazaflavin series inhibits TDP2 enzyme activity in a fluorescence-based assay, suitable for high-throughput screen (HTS)-screening. We have gone on to determine crystal structures of these compounds bound to a 'humanized' form of murine TDP2. The structures reveal their novel mode of action as competitive ligands for the binding site of an incoming DNA substrate, and point the way to generating novel and potent inhibitors of TDP2.

Can the inpatient hospital setting be a golden opportunity to improve colon cancer screening rates in the United States?

BACKGROUND: Colorectal cancer is the third most common cancer in the United States. Despite efforts to increase colorectal cancer screening, the rate of compliance with the recommended screening remains relatively suboptimal according the American Cancer Society (53%). PURPOSE: To assess whether the time of hospitalization is a suitable opportunity for patients to receive counseling and for recruiting patients to undergo screening colonoscopy for colon cancer. METHOD: In 2009, we conducted a cross-sectional survey of hospitalized adults age 50 to 80 years in order to assess their responses on a modified version of the Health Information National Trends Survey. We conducted χ(2) analyses on these data to examine the differences in patients' knowledge of colorectal cancer screening and prior adherence to screening guidelines and to assess whether they would be willing to undergo a screening in the near future if prompted by their physicians. RESULTS: We enrolled a total of 332 participants to complete the study questionnaire. About 94% of the subjects had heard about colon cancer, and 83.4% had heard of any screening tests to detect colorectal cancer. About 66% of subjects reported the colonoscopy to be the most effective screening test for colon cancer. Approximately 55% of the total sample group adhered to recommended screening guidelines for colon cancer using the colonoscopy. CONCLUSIONS: The time of hospitalization is a potential "golden opportunity" to counsel patients and promote colon cancer screening.

Generation of assays and antibodies to facilitate the study of human 5'-tyrosyl DNA phosphodiesterase.

Topoisomerases regulate DNA topology by the transient cleavage and religation of DNA during transcription and replication. Topoisomerase II (Topo II) poisons such as etoposide can induce abortive DNA strand breaks in which Topo II remains covalently bound to a 5' DNA strand terminus via a phosphotyrosyl linker. Tyrosyl DNA phosphodiesterase 2 (Tdp2) is a recently discovered human 5'-tyrosyl DNA phosphodiesterase that repairs this topoisomerase-mediated DNA damage, thereby playing a central role in maintaining normal DNA topology in cells. Cellular depletion of Tdp2 has been shown to result in increased susceptibility and sensitivity to Topo II-induced DNA double-strand breaks, thereby revealing Tdp2 as a potentially attractive anticancer target. No drug-like inhibitors of Tdp2 have been identified to date, and assays suitable for high-throughput screening (HTS) have not been widely reported. Here we have identified a new and effective chromogenic substrate for Tdp2 and developed a homogeneous and robust HTS assay. A second novel Tdp2 assay was also developed to cross-validate hit matter identified from an HTS. In addition, a new and specific Tdp2 antibody is described. Together, these new tools will aid in the identification of novel Tdp2 inhibitors and the investigation of the role of Tdp2 in cancer.

Effectiveness and safety of raloxifene in post-menopausal females.

OBJECTIVE: To determine effects of raloxifene on lipid profile, breast tissue and endometrial thickness in post-menopausal women. DESIGN: A longitudinal cohort study. PLACE AND DURATION OF STUDY: The study was conducted at Department of Gynaecology and Obstetrics, PNS Shifa Hospital, Karachi over a period of one year. PATIENTS AND METHODS: Fifty cases of postmenopausal women, aged 45-60 years, who had last menstrual period 2-8 years back, visiting Gynea OPD at PNS Shifa Hospital, Karachi, were included in the study. The subject received raloxifene (Evista) 60 mg once daily. The tests done at the start of study as baseline were serum lipid profile (HDL, LDL, total triglyceride and cholesterol levels), TVS (trans vaginal sonography) for endometrial thickness and mammography. The above tests were again done at the end of study after 12 months. The adverse effects were recorded. RESULTS: Fifty women were enrolled for study out of which 48 completed the study that is 96%. Mean age was 54 years, SD = 3.95. The mean value of LDL, total triglyceride and cholesterol decreased by 15.2%, 1.2% and 10.2 % respectively. The change was statistically significant. (p < 0.001) HDL change was 0.665% and was not statistically significant. TVS, for endometrial thickness, and mammography for breast density showed no change. Adverse effects reported were hot flushes, leg cramps and vaginal symptoms in few cases. CONCLUSION: Raloxifene therapy significantly decreases cardiovascular risk markers LDL, total triglyceride and cholesterol. No abnormal change in breast density and in endometrial thickness indicate good safety profile of this agent.