Ribose Moieties Acylation and Characterization of Some Cytidine Analogs

Modification of naturally occurring nucleosides is an important area in the search for new agents with therapeutic potential. In this study, nucleoside molecules, that is, cytidine analogs bearing ribose moieties were successfully synthesized to obtain 5´-O-acyl cytidine (2), which in turn was converted into 2´,3´-di-O-acyl cytidine (3–7) through direct acylation. Similarly, several cytidine analogs (8–15) were formed using the aforementioned technique. Physicochemical properties and spectroscopic methods were used to characterize the newly synthesized cytidine analogs. X-ray powder diffraction was employed for quantitatively identifying crystalline compounds. Hence, these synthesized derivatives can be used as potential antimicrobial agents and promising drug candidates

Mutagen Synergy: Hypermutability Generated by Specific Pairs of Base Analogs

ABSTRACTWe tested pairwise combinations of classical base analog mutagens inEscherichia colito study possible mutagen synergies. We examined the cytidine analogs zebularine (ZEB) and 5-azacytidine (5AZ), the adenine analog 2-aminopurine (2AP), and the uridine/thymidine analog 5-bromodeoxyuridine (5BrdU). We detected a striking synergy with the 2AP plus ZEB combination, resulting in hypermutability, a 35-fold increase in mutation frequency (to 53,000 × 10−8) in therpoBgene over that with either mutagen alone. A weak synergy was also detected with 2AP plus 5AZ and with 5BrdU plus ZEB. The pairing of 2AP and 5BrdU resulted in suppression, lowering the mutation frequency of 5BrdU alone by 6.5-fold. Sequencing the mutations from the 2AP plus ZEB combination showed the predominance of two new hot spots for A·T→G·C transitions that are not well represented in either single mutagen spectrum, and one of which is not found even in the spectrum of a mismatch repair-deficient strain. The strong synergy between 2AP and ZEB could be explained by changes in the dinucleoside triphosphate (dNTP) pools.IMPORTANCEAlthough mutagens have been widely studied, the mutagenic effects of combinations of mutagens have not been fully researched. Here, we show that certain pairwise combinations of base analog mutagens display synergy or suppression. In particular, the combination of 2-aminopurine and zebularine, analogs of adenine and cytidine, respectively, shows a 35-fold increased mutation frequency compared with that of either mutagen alone. Understanding the mechanism of synergy can lead to increased understanding of mutagenic processes. As combinations of base analogs are used in certain chemotherapy regimens, including those involving ZEB and 5AZ, these results indicate that testing the mutagenicity of all drug combinations is prudent.

Ranking small molecules by how much they preferentially inhibit the growth of cancer cell lines with either BRAF or KRAS oncogene mutations

We were interested in the question of whether it might be possible to use knowledge of cancer-related mutations in the cell lines of the NCI60 screening data set to identify small molecules that preferentially inhibit the growth of cell lines containing either BRAF or KRAS oncogene mutations. Our hypothesis was that this cell line mutation knowledge could help to identify small molecules that were more likely to preferentially inhibit growth of cell lines with a particular mutation. It seems that any such molecules might be further investigated to try to better understand the molecular mechanisms of growth inhibition. We defined a quantity, \(\text{Diff}_{\text{mut}}\), that estimates how much more a given small molecule inhibits cell lines with a mutation of interest than cell lines without that mutation. We ranked the small molecules in descending order of \(\text{Diff}_{\text{mut}}\) and then tried to explain whether the ranking of the highest ranked molecules made sense in terms of independent facts about these molecules. This method showed the BRAF inhibitor vemurafenib to be highly ranked in the BRAF ranking. The cytidine analog cytarabine was found to be highly ranked in the KRAS ranking. Other cytidine analogs were also found to be highly ranked with respect to KRAS.

Ranking small molecules by how much they preferentially inhibit the growth of cancer cell lines with either BRAF or KRAS oncogene mutations

We were interested in the question of whether it might be possible to use knowledge of cancer-related mutations in the cell lines of the NCI60 screening data set to identify small molecules that preferentially inhibit the growth of cell lines containing either BRAF or KRAS oncogene mutations. Our hypothesis was that this cell line mutation knowledge could help to identify small molecules that were more likely to preferentially inhibit growth of cell lines with a particular mutation. It seems that any such molecules might be further investigated to try to better understand the molecular mechanisms of growth inhibition. We defined a quantity, \(\text{Diff}_{\text{mut}}\), that estimates how much more a given small molecule inhibits cell lines with a mutation of interest than cell lines without that mutation. We ranked the small molecules in descending order of \(\text{Diff}_{\text{mut}}\) and then tried to explain whether the ranking of the highest ranked molecules made sense in terms of independent facts about these molecules. This method showed the BRAF inhibitor vemurafenib to be highly ranked in the BRAF ranking. The cytidine analog cytarabine was found to be highly ranked in the KRAS ranking. Other cytidine analogs were also found to be highly ranked with respect to KRAS.