Insights into pralsetinib resistance to the non-gatekeeper RET kinase G810C mutation through molecular dynamics simulations.

OBJECTIVE: RET (rearranged during transfection) kinase, as a transmembrane receptor tyrosine kinase, is a therapeutic target for several human cancer such as non-small cell lung cancer (NSCLC) and thyroid cancer. Pralsetinib is a recently approved drug for the treatment of RET-driven NSCLC and thyroid cancers. A single point mutation G810C at the C-lobe of the RET kinase causes pralsetinib resistance to this non-gatekeeper variant. However, the detailed mechanism remains poorly understood. METHODS: Here, multiple microsecond molecular dynamics (MD) simulations, molecular mechanics/generalized born surface area (MM/GBSA) binding free energy calculations, and community network analysis were performed to reveal the mechanism of pralsetinib resistance to the RET G810C mutant. RESULTS: The simulations showed that the G810C mutation had a minor effect on the overall conformational dynamics of the RET kinase domain. Energetic analysis suggested that the G810C mutation reduced the binding affinity of pralsetinib to the mutant. Per-residue energy contribution and structural analyses revealed that the hydrogen bonding interactions between pralsetinib and the hinge residues Glu805 and Ala807 were disrupted in the G810C mutant, which were responsible for the decreased binding affinity of pralsetinib to the mutant. CONCLUSIONS: The obtained results may provide understanding of the mechanism of pralsetinib resistance to the non-gatekeeper RET G810C mutant.

[Experimental varicocele affects the ipsilateral testis in rats].

OBJECTIVE: To investigate the impact of experimental varicocele (EV) on the ipsilateral testis in rats. METHODS: EV was induced by partial ligation of the left renal vein in male SD rats, the control rats subjected to sham operation, and the testes of the EV models and controls were extirpated 6, 12, and 18 weeks later. Johnson's score, ultrastructure of seminiferous tubules, intratesticular testosterone concentration (ITC) and germ cell apoptotic index (AI) of each left testis were evaluated. RESULTS: Johnson's scores were (6.92 +/- 0.52), (4.83 +/- 0.41) and (2.95 +/- 0.26), ITCswere (6.32 +/- 0.85), (5.17 +/- 0.76) and (4.11 +/- 0.69) and AIs were (5.32 +/- 1.23), (15.21 +/- 0.97) and (21.13 +/- 1.12) respectively in the 6 w , 12 w and 18 w EV groups, significantly lower than in the corresponding control groups, (9.56 +/- 0.35, 9.63 +/- 0.31, 9.39 +/- 0.46), (9.64 +/- 1.23, 9.38 +/- 0.69, 9.73 +/- 0.49) and (3.21 +/- 1.15, 3.43 +/- 1.21, 3.61 +/- 1. 15) (P < 0.05), the former two showing a gradual decline while the latter a significant elevation with the increasing duration of varicocele. The damage to the ultrastructure of seminiferous tubules was aggravated with the prolonging of varicocele. CONCLUSION: EV can cause a progressive decline of ITC, dyszoospermia and increased AI of germ cells.