OBJECTIVETo investigate the effects of embryo cryopreservation and thawing on clinical outcomes of transplantable embryos after preimplantation genetic diagnosis (PGD) or preimplantation genetic screening (PGS) in cleavage-stage.

METHODSThe clinical data of 302 cases (including 118 cases using frozen/thawing embryos and 184 cases using fresh embryos) undergoing PGD/PGS in Women's Hospital, Zhejiang University School of Medicine during January 2011 and December 2016 were retrospectively analyzed. The pregnancy rate, implantation rate, live birth rate and abortion rate of fresh and frozen-thawed embryo transfer (FET) cycles were compared. And the influencing factors for pregnancy outcome was analyzed by multivariate logistic regression.

RESULTSThe rate of normal or balanced translocation embryos in fresh cycle was higher than that in FET cycle (23.52% vs 16.67%,<0.05), and the average number of transplanted embryos was more than that in FET cycle (1.54±0.56 vs 1.33±0.51,<0.05). But there were no significant differences in pregnancy rate (36.42% vs 40.00%,>0.05), implantation rate (26.62% vs 32.91%,>0.05), abortion rate (19.44% vs 8.33%,>0.05) and live birth rate (25.96% vs 28.33%,>0.05) between fresh cycle and FET cycle. Multivariate logistic regression showed that, parent ages, embryo status (fresh or frozen), the mode of PGD/PGS and the findings of PGD/PGS had no impact on pregnancy outcome (all>0.05).

CONCLUSIONSCryopreservation do not have significant effects on the clinical outcomes of transplantable embryos after PGD/PGS in cleavage-stage.

Chemotherapy is one of the important methods to treat cancer, and the emergence of multidrug resistance (MDR) is one major cause for the failure of cancer chemotherapy. Almost all anti-tumor drugs develop drug resistance over a period of time of application in cancer patients, reducing their effects on killing cancer cells. Chemoresistance can lead to a rapid recurrence of cancers and ultimately patient death. MDR may be induced by multiple mechanisms, which are associated with a complex process of multiple genes, factors, pathways, and multiple steps, and today the MDR-associated mechanisms are largely unknown. In this paper, from the aspects of protein-protein interactions, alternative splicing (AS) in pre-mRNA, non-coding RNA (ncRNA) mediation, genome mutations, variance in cell functions, and influence from the tumor microenvironment, we summarize the molecular mechanisms associated with MDR in cancers. In the end, prospects for the exploration of antitumor drugs that can reverse MDR are briefly discussed from the angle of drug systems with improved targeting properties, biocompatibility, availability, and other advantages.