Phenyl-substituted aminomethylene-bisphosphonates inhibit human P5C reductase and show antiproliferative activity against proline-hyperproducing tumour cells

Abstract

In certain cancers, such as breast, prostate and some lung and skin cancers, the gene for the enzyme catalysing the second and last step in proline synthesis, d 1 -pyrroline-5-carboxylate (P5C) reductase, has been found upregulated. This leads to a higher proline content that exacerbates the effects of the so-called proline-P5C cycle, with tumour cells effectively using this method to increase cell survival. If a method of reducing or inhibiting P5C reductase could be discovered, it would provide new means of treating cancer. To address this point, the effect of some phenyl-substituted derivatives of aminomethylene-bisphosphonic acid, previously found to interfere with the catalytic activity of plant and bacterial P5C reductases, was evaluated in vitro on the human isoform 1 (PYCR1), expressed in E. coli and affinity purified. The 3.5-dibromophenyl-and 3.5-dichlorophenyl-derivatives showed a remarkable effectiveness, with IC 50 values lower than 1 mM and a mechanism of competitive type against both P5C and NADPH. The actual occurrence in vivo of enzyme inhibition was assessed on myelogenous erythroleukemic K562 and epithelial breast cancer MDA-MB-231 cell lines, whose growth was progressively impaired by concentrations of the dibromo derivative ranging from 10 À6 to 10 À4 M. Interestingly, growth inhibition was not relieved by the exogenous supply of proline, suggesting that the effect relies on the interference with the proline-P5C cycle, and not on proline starvation.

Perspectives, past, present and future: the proline cycle/proline-collagen regulatory axis

“…These are published reports of inhibitors of the proline regulated axis and its downstream effectors (D'Aniello et al 2020 ). A recent report identified Phenyl-substituted aminomethylene bisphonates as inhibitors of human P5C reductase and antiproliferative activity in tumor cells (Forlani et al 2021 ). Hopefully, many others will emerge and future clinical trials especially as adjuncts for chemotherapy drugs may lead to novel therapies.…”

Proline metabolism reprogramming of trained macrophages induced by early respiratory infection combined with allergen sensitization contributes to development of allergic asthma in childhood of mice

“…Mice were sensitized with PVM-OVA, PVM-OVA followed by BPTES or NFLP, or PVM-OVA followed by BPTES+Proline or NFLP +Proline, and challenged with OVA after 21 days post infection. PYCR1 was obviously reduced in PVM-OVA group, compared with that in PBS group (Figure 4E, P<0.05), which may be due to feedback inhibition of increased proline (32). All of the data suggested that proline synthesis pathway is remarkably active in PVM-OVA group.…”

“…The relative expression of GLS1 or GLS2 significantly increased in PVM-OVA group, compared with that in PBS group, which was consistent with the change of proline ( Figure 4E , P<0.05). However, the expression of PYCR1 was obviously reduced in PVM-OVA group, compared with that in PBS group ( Figure 4E , P<0.05), which may be due to feedback inhibition of increased proline ( 32 ). All of the data suggested that proline synthesis pathway is remarkably active in PVM-OVA group.…”

The Multifaceted Roles of Proline in Cell Behavior

“…Likewise, up-regulation of L-Pro biosynthesis genes (ALDH18A1 and PYCR1) also reveals L-Pro starvation in tumor cells (D'Aniello et al, 2020). Moreover, ALDH18A1 knock-down activates AAR stress signaling, and reduces melanoma tumor growth both in vitro and in vivo (Kardos et al, 2015), whereas PYCR1 induction improves proliferation and invasiveness of breast, esophagus, lung, melanoma, pancreas, and prostate cancer cells (Nilsson et al, 2014;Ding et al, 2017;Zeng et al, 2017;Cai et al, 2018;Ye et al, 2018;Kardos et al, 2020;Forlani et al, 2021). Of note, kindlerin 2 (KINDLING-2) protein stabilizes the mitochondrial PYCR1 enzyme, increasing L-Pro synthesis and lung adenocarcinoma cell proliferation (Guo et al, 2019).…”