Green versus blue: Randomized controlled trial comparing indocyanine green with methylene blue for sentinel lymph node detection in endometrial cancer.

OBJECTIVE: To ascertain the increase in detection rate of sentinel lymph node (SLN) associated with the use of indocyanine green (ICG) in comparison with methylene blue dye in women with endometrial cancer. METHODS: For this randomized controlled trial, all patients underwent SLN mapping after injection of blue dye on one side of the cervix and ICG on the other side. Randomization was for the side (right vs. left) on which ICG was used so that each patient's contralateral hemipelvis (HP) served as a control to her ipsilateral HP. We performed a two-tailed, normal-approximate McNemar test for paired-matched data. The primary endpoint was the difference in SLN detection rate for each HP according to the dye used. RESULTS: This trial included 132 patients, and 46 patients underwent robotic-assisted surgery while 86 had standard laparoscopic surgery. Successful detection of SLN was 90.9% using ICG and 64.4% using blue dye (p < 0.0001). There were no differences in the duration of the SLN procedure (median 10 min per HP) and number of SLN per HP (mean 1.2) according to the dye used. The SLN detection rates for either dye were very similar whether the surgical approach was robotic (mean BMI 45) or laparoscopic (mean BMI 29). Crossover of dye to the contralateral HP was present in 3% of cases. CONCLUSION: The use of ICG instead of blue dye results in a 26.5% (95% CI 17.4%-35.6%) increase of SLN detection rates per HP in women with endometrial cancer.

DNMT1 is required to maintain CpG methylation and aberrant gene silencing in human cancer cells.

Transcriptional silencing by CpG island methylation is a prevalent mechanism of tumor-suppressor gene suppression in cancers. Genetic experiments have defined the importance of the DNA methyltransferase Dnmt1 for the maintenance of methylation in mouse cells and its role in neoplasia. In human bladder cancer cells, selective depletion of DNMT1 with antisense inhibitors has been shown to induce demethylation and reactivation of the silenced tumor-suppressor gene CDKN2A. In contrast, targeted disruption of DNMT1 alleles in HCT116 human colon cancer cells produced clones that retained CpG island methylation and associated tumor-suppressor gene silencing, whereas HCT116 clones with inactivation of both DNMT1 and DNMT3B showed much lower levels of DNA methylation, suggesting that the two enzymes are highly cooperative. We used a combination of genetic (antisense and siRNA) and pharmacologic (5-aza-2'-deoxycytidine) inhibitors of DNA methyl transferases to study the contribution of the DNMT isotypes to cancer-cell methylation. Selective depletion of DNMT1 using either antisense or siRNA resulted in lower cellular maintenance methyltransferase activity, global and gene-specific demethylation and re-expression of tumor-suppressor genes in human cancer cells. Specific depletion of DNMT1 but not DNMT3A or DNMT3B markedly potentiated the ability of 5-aza-2'-deoxycytidine to reactivate silenced tumor-suppressor genes, indicating that inhibition of DNMT1 function is the principal means by which 5-aza-2'-deoxycytidine reactivates genes. These results indicate that DNMT1 is necessary and sufficient to maintain global methylation and aberrant CpG island methylation in human cancer cells.

Constrained (l-)-S-adenosyl-l-homocysteine (SAH) analogues as DNA methyltransferase inhibitors.

Potent SAH analogues with constrained homocysteine units have been designed and synthesized as inhibitors of human DNMT enzymes. The five membered (2S,4S)-4-mercaptopyrrolidine-2-carboxylic acid, in 1a, was a good replacement for homocysteine, while the corresponding six-member counterpart was less active. Further optimization of 1a, changed the selectivity profile of these inhibitors. A Chloro substituent at the 2-position of 1a, compound 1d, retained potency against DNMT1, while N(6) alkylation, compound 7a, conserved DNMT3b2 activity. The concomitant substitutions of 1a at both 2- and N(6) positions reduced activity against both enzymes.