Discovery and characterization of novel peptide inhibitors of the NRF2/MAFG/DNA ternary complex for the treatment of cancer

Pathway activating mutations of the transcription factor NRF2 and its negative regulator KEAP1 are strongly correlative with poor clinical outcome with pemetrexed/carbo(cis)platin/pembrolizumab (PCP) chemo-immunotherapy in lung cancer. Despite the strong genetic support and therapeutic potential for a NRF2 transcriptional inhibitor, currently there are no known direct inhibitors of the NRF2 protein or its complexes with MAF and/or DNA. Herein we describe the design of a novel and high-confidence homology model to guide a medicinal chemistry effort that resulted in the discovery of a series of peptides that demonstrate high affinity, selective binding to the Antioxidant Response Element (ARE) DNA and thereby displace NRF2-MAFG from its promoter, which is an inhibitory mechanism that to our knowledge has not been previously described. In addition to their activity in electrophoretic mobility shift (EMSA) and TR-FRET-based assays, we show significant dose-dependent ternary complex disruption of NRF2-MAFG binding to DNA by SPR, as well as cellular target engagement by thermal destabilization of HiBiT-tagged NRF2 in the NCI-H1944 NSCLC cell line upon digitonin permeabilization, and SAR studies leading to improved cellular stability. We report the characterization and unique profile of lead peptide 18, which we believe to be a useful in vitro tool to probe NRF2 biology in cancer cell lines and models, while also serving as an excellent starting point for additional in vivo optimization toward inhibition of NRF2-driven transcription to address a significant unmet medical need in non-small cell lung cancer (NSCLC).

FSH, the neglected sibling: evidence for its role in regulation of spermatogenesis and Leydig cell function

The role of follicle stimulating harmone(FSH) in male reproductive function remains a matter of debate although recent evidences strongly suggest a role despite the controversies that arose following the results obtained with FSH-beta null mice and observations from human FSH receptor mutations. This review summarizes the recent developments of our understanding on the role of FSH in male reproduction. Specifically the results obtained with FSH-beta and FORKO null mice are be discussed in light of our observations employing active and passive neutralization of endogenous FSH in rodents and primates along with other studies. On the basis of results obtained employing a variety of models it can be conclude unequivocally that FSH regulates Leydig cell function and is essential for normal quantitative spermatogenesis.

Evaluation of relative role of LH and FSH in restoration of spermatogenesis using ethanedimethylsulphonate-treated adult rats

Spermatogenesis is a complex process, and previous studies have clearly established the role for testosterone in its maintenance. However, the role of FSH remains controversial, although several lines of evidence suggest its importance in initiation of spermatogenesis. In the present study, the relative roles of FSH and LH have been evaluated using specific antisera capable of neutralizing endogenous hormones in adult male rats following ethanedimethylsulphonate (EDS) treatment. Restoration of spermatogenesis in EDS-treated rats was monitored following FSH or LH deprivation by histological analysis and flow cytometry. Deprivation of FSH resulted in a reduction of seminiferous tubule diameter and spermatogonial number, which was much more drastic than that observed following LH deprivation. More importantly, FSH deprivation was associated with a significant reduction in the number of pachytene spermatocytes. These results provide evidence for a definite role for FSH in regulation of spermatogenesis, in addition to confirming the role of LH in spermatogenesis via testosterone.

Isolation and characterization of Leydig cells from adult bonnet monkeys (Macaca radiata): evidence for low steroidogenic capacity in monkey Leydig cells in contrast to rat Leydig cells

Most of the available information on Leydig cells has been obtained using a rodent model system. With an objective to extend the observations made with rat Leydig cells (RLCs) to primates, a method has been developed to isolate Leydig cells from monkey (Macaca radiata) testis. Enzymatic dissociation of monkey testis followed by Percoll-gradient fractionation of the interstitial cells resulted in the recovery of Leydig cells at densities corresponding to 1.064-1.070 g/ml. Purified (90-94%) monkey Leydig cells (MLCs) stained positive for the Leydig cell marker 3beta-hydroxysteroid dehydrogenase. The cells responded to in vitro addition of human chorionic gonadotropin (hCG) and produced testosterone. Comparison of the in vitro testosterone-producing ability of MLCs with RLCs revealed that MLCs have much less steroidogenic capacity compared with the RLCs. Analysis revealed that limitation in substrate availability to mitochondrial P(450) side chain cleavage enzyme and low mitochondrial and smooth endoplasmic reticulum content in MLCs could be the possible reasons for the low steroidogenic capacity of the MLCs.

A preliminary study on the possible role for luteinizing hormone in androgen independent growth of prostate

The recent observation that LH receptors are found in the prostate and that LH can execute a mitogenic role in addition to its well documented role in stimulation of steroidogenesis prompted the evaluation of the role of LH in regulation of prostate growth. The results obtained in the present study reveal the presence of LH receptor transcript as well as receptor protein in the rat prostate. The LH receptor appears to be localized in the non-secretory epithelial cells of the prostate as assessed by I(125) LH binding and immunofluorescence. Addition of HCG to purified prostate cells resulted in an increase in bromodeoxyuridine incorporation only in the non-secretory epithelial cells. Using a castrated adult rat model system, it has also been observed that LH receptor is regulated by LH itself, and that LH also regulates protein synthesis in the prostate. In addition, it has been possible to demonstrate the presence of LH receptor in the prostate from cases of human benign prostate hyperplasia. These results suggest a possible role for LH in the regulation of prostate growth.

Evaluation of relative roles of LH and FSH in regulation of differentiation of Leydig cells using an ethane 1,2-dimethylsulfonate-treated adult rat model

The relative role of LH and FSH in regulation of differentiation of Leydig cells was assessed using an ethane 1,2-dimethylsulfonate (EDS)-treated rat model in which endogenous LH or FSH was neutralized from day 3 to day 22 following EDS treatment. Serum testosterone and the in vitro response of the purified Leydig cells to human chorionic gonadotropin (hCG) was monitored. In addition RNA was isolated from the Leydig cells to monitor the steady-state mRNA levels by RT-PCR for 17alpha-hydroxylase, side chain cleavage enzyme, steroidogenic acute regulatory protein (StAR), LH receptor, estrogen receptor (ER-alpha) and cyclophilin (internal control). Serum testosterone was undetected and the isolated Leydig cells secreted negligible amount of testosterone on stimulation with hCG in the group of rats that were treated with LH antiserum following EDS treatment. RT-PCR analysis revealed the absence of message for cholesterol side chain cleavage enzyme and 17alpha-hydroxylase although ER-alpha and LH receptor mRNA could be detected, indicating the presence of undifferentiated precursor Leydig cells. In contrast, the effects following deprival of endogenous FSH were not as drastic as seen following LH neutralization. Deprival of endogenous FSH in EDS-treated rats led to a significant decrease in serum testosterone and in vitro response to hCG by the Leydig cells. Also, there was a significant decrease in the steady-state mRNA levels of 17alpha-hydroxylase, cholesterol side chain cleavage enzyme, LH receptor and StAR as assessed by a semiquantitative RT-PCR. These results establish that while LH is obligatory for the functional differentiation of Leydig cells, repopulation of precursor Leydig cells is independent of LH, and also unequivocally establish an important role for FSH in regulation of Leydig cell function.

Müllerian inhibiting substance inhibits testosterone synthesis in adult rats

Müllerian inhibiting substance (MIS) is a gonadal hormone that causes regression of the Müllerian ducts during male sexual differentiation. Postnatally, MIS inhibits the proliferation and differentiation of immature Leydig cells, and transgenic mice that overexpress MIS have decreased serum testosterone concentrations. To elucidate the effects of MIS on androgen regulation in the postnatal testis, we examined testosterone synthesis in adult Sprague-Dawley rats following intratesticular and intraperitoneal injections of MIS. Intratesticular MIS injection achieved high local concentrations of MIS (574.0 +/- 60.0 ng/mL) at 4 hours, with a corresponding decline in serum testosterone concentrations to 0.7 +/- 0.1 ng/mL, compared to 1.1 +/- 0.2 ng/mL with intraperitoneal MIS and 1.6 +/- 0.1 ng/mL with intratesticular vehicle (IT-Veh) (P < .001). Intratesticular administration of MIS (IT-MIS) resulted in much higher serum and testicular interstitial fluid MIS concentrations than the intraperitoneal route. To directly examine the testosterone production rate in MIS-treated animals, we isolated Leydig cells from MIS and vehicle-injected testes. Primary Leydig cells exposed to MIS had a lower testosterone production rate and decreased expression of p450c17 (hydroxylase/lyase) and luteinizing hormone (LH) receptor mRNAs than that of vehicle-injected controls or the noninjected contralateral testis. In conclusion, intratesticular administration of MIS caused a decline in serum testosterone concentrations by decreasing the rate of testosterone biosynthesis, confirming that MIS can regulate adult Leydig cell androgen production. The ability of MIS to down-regulate mRNA expression of the p450c17 and LH receptor genes suggests that this effect is mediated transcriptionally. These data indicate that, in addition to its role in embryonic differentiation of the male reproductive tract, MIS has a regulatory function in the postnatal testis. We conclude that one such function is for MIS to directly inhibit adult Leydig cell steroidogenesis.

Effect of deprival of LH on Leydig cell proliferation: involvement of PCNA, cyclin D3 and IGF-1

The levels of proliferating cell nuclear antigen (PCNA) and cyclin D3 which are known markers of cellular proliferation were monitored by immunoblotting in progenitor Leydig cells (PLC), immature Leydig cells (ILC) and adult Leydig cells (ALC) isolated from 21, 35 and 90 day old rats, respectively which represent the Leydig cells at different stages of development. The levels of PCNA and cyclin D3 were highest in PLC, intermediate in ILC and lowest in ALC. Following administration of an antiserum to LH to deprive endogenous LH in 21 day old rats, a significant decrease in the levels of PCNA and Cyclin D3 were observed suggesting the involvement of Lutenizing hormone (LH) in PLC proliferation. In support of this observation, Bromodeoxyuridine (BrdU) incorporation was highest in PLC when compared with ILC and ALC, and administration of LH antiserum to 21 day old rats led to a total absence of BrdU incorporation by the isolated PLC. Also, there was a decrease in the level of IGF-1 and IGF-1 receptor mRNA levels by 55 and 35%, respectively as assessed by semi-quantitative RT-PCR. In addition, the PLC isolated from rats deprived of endogenous LH incorporated much less BrdU following addition of IGF-1. These results, which are obtained using an in vivo model system establish that LH has a very important role in Leydig cell proliferation in immature rats.

Ethane dimethylsulphonate selectively destroys Leydig cells in the adult bonnet monkeys (Macaca radiata)

AIM

To study the effect of intratesticular administration of ethane-1,2-dimethylsulphonate (EDS) which has been extensively used to selectively destroy Leydig cells in rats and study the role of gonadotropin in regulation of differentiation of Leydig cells (LC) in the adult male bonnet monkey.

METHODS AND RESULTS

In vitro studies with cultured interstitial cells isolated from monkey testis revealed an inhibitory effect of EDS on LC as assessed by decrease in testosterone production. Intratesticular administration of EDS (5, 10, 20, 50 mg/testis) resulted in a dose-dependent rapid decrease in serum testosterone levels, with a 65% decrease with 5 mg of EDS by the 3rd day, which returned to control levels by the 45th day. EDS treatment resulted in a significant decrease in testicular testosterone. In addition a significant decrease in [125I]hCG binding and phenylesterase activity in the interstitial cells was noticed. Histological analysis of the testes on the 5th day after administration of EDS revealed an interstitium devoid of LC indicating the destructive action of EDS.

CONCLUSION

The monkey LC are sensitive to destructive action of EDS.