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Multidrug resistance-associated proteins are ABC C-family exporters. They are crucial in pharmacology as they transport various substrates across membranes. However, the role of the degenerate nucleotide-binding site (NBS) remains unclear likewise the interplay with the surrounding lipid environment. Here, we propose a dynamic and structural overview of MRP1 from ca. 110 μs molecular dynamics simulations. ATP binding to NBS1 is likely maintained along several transport cycles. Asymmetric NBD behaviour is ensured by lower signal transduction from NBD1 to the rest of the protein owing to the absence of ball-and-socket conformation between NBD1 and coupling helices. Even though surrounding lipids play an active role in the allosteric communication between the substrate-binding pocket and NBDs, our results suggest that lipid composition has a limited impact, mostly by affecting transport kinetics. We believe that our work can be extended to other degenerate NBS ABC proteins and provide hints for deciphering mechanistic differences among ABC transporters.

Retrospective series suggest that bevacizumab-induced hypertension (HTN) is a prognostic and potentially predictive biomarker of efficacy of the antiangiogenic drug in the upfront treatment of metastatic colorectal cancer (mCRC) patients. The immortal-time bias and the effect of pre-existing HTN might affect these findings. We conducted a pooled, post hoc analysis of 2 prospective randomized trials of chemotherapy plus bevacizumab in mCRC, and performed a systematic review of the available literature focusing on how the immortal-time bias was taken into account and how pre-existing HTN potentially requiring the use of antihypertensive drugs was managed.The pooled-analysis included patients enrolled in the phase III TRIBE and TRIBE-2 studies that compared upfront FOLFOXIRI + bevacizumab to FOLFIRI or FOLFOX + bevacizumab, respectively. Association between HTN and survival outcomes was assessed by incorporating a time-dependent Cox regression model to consider the time-dependency of the probability of HTN onset during the treatment. The systematic review was conducted according to PRISMA guidelines.The systematic review retrieved 14 eligible and highly heterogeneous studies. A positive prognostic impact of bevacizumab-induced HTN was reported in the 58% of the analyses reporting Progression Free Survival (PFS) and in the 54% of the analyses reporting Overall Survival (OS) data. Immortal-time bias was incorporated in 4 studies (28%). In TRIBE and TRIBE-2 study populations (N = 1175), patients experiencing ≥ G2 HTN during first-line bevacizumab administration showed longer PFS (median: 14.7 versus 10.3 months, p 0.001) and OS (median: 31.7 versus 24.2 months, p 0.001). The association with OS retained statistical significance after correction for time-dependency (p = 0.003) and was confirmed in the multivariable model including HTN as a time-dependent variable (p = 0.02). Moreover, in patients with pre-existing HTN, no difference in terms of PFS and OS was observed compared with the subgroup of patients who never experienced ≥G2 HTN (HR 1.01, p = 0.86 and HR 1.02, p = 0.78 respectively.Bevacizumab-induced HTN during the first-line treatment of mCRC is an independent prognostic factor, also adopting a time-dependency correction. Toxicity should be interpreted as a time-dependent variable when exploring its association with clinical outcome.