VNLG-152R and its deuterated analogs potently inhibit/repress triple/quadruple negative breast cancer of diverse racial origins in vitro and in vivo by upregulating E3 Ligase Synoviolin 1 (SYVN1) and inducing proteasomal degradation of MNK1/2.

Triple-negative breast cancer (TNBC) and its recently identified subtype, quadruple negative breast cancer (QNBC), collectively account for approximately 13% of reported breast cancer cases in the United States. These aggressive forms of breast cancer are associated with poor prognoses, limited treatment options, and lower overall survival rates. In previous studies, our research demonstrated that VNLG-152R exhibits inhibitory effects on TNBC cells both in vitro and in vivo and the deuterated analogs were more potent inhibitors of TNBC cells in vitro. Building upon these findings, our current study delves into the molecular mechanisms underlying this inhibitory action. Through transcriptome and proteome analyses, we discovered that VNLG-152R upregulates the expression of E3 ligase Synoviolin 1 (SYVN1), also called 3-hydroxy-3-methylglutaryl reductase degradation (HRD1) in TNBC cells. Moreover, we provide genetic and pharmacological evidence to demonstrate that SYVN1 mediates the ubiquitination and subsequent proteasomal degradation of MNK1/2, the only known kinases responsible for phosphorylating eIF4E. Phosphorylation of eIF4E being a rate-limiting step in the formation of the eIF4F translation initiation complex, the degradation of MNK1/2 by VNLG-152R and its analogs impedes dysregulated translation in TNBC cells, resulting in the inhibition of tumor growth. Importantly, our findings were validated in vivo using TNBC xenograft models derived from MDA-MB-231, MDA-MB-468, and MDA-MB-453 cell lines, representing different racial origins and genetic backgrounds. These xenograft models, which encompass TNBCs with varying androgen receptor (AR) expression levels, were effectively inhibited by oral administration of VNLG-152R and its deuterated analogs in NRG mice. Importantly, in direct comparison, our compounds are more effective than enzalutamide and docetaxel in achieving tumor growth inhibition/repression in the AR+ MDA-MD-453 xenograft model in mice. Collectively, our study sheds light on the involvement of SYVN1 E3 ligase in the VNLG-152R-induced degradation of MNK1/2 and the therapeutic potential of VNLG-152R and its more potent deuterated analogs as promising agents for the treatment of TNBC across diverse patient populations.

Galeterone and The Next Generation Galeterone Analogs, VNPP414 and VNPP433-3ß Exert Potent Therapeutic Effects in Castration-/Drug-Resistant Prostate Cancer Preclinical Models In Vitro and In Vivo.

These studies compared the efficacies of our clinical agent galeterone (Gal) and the FDA-approved prostate cancer drug, enzalutamide (ENZ) with two lead next generation galeterone analogs (NGGAs), VNPP414 and VNPP433-3ß, using prostate cancer (PC) in vitro and in vivo models. Antitumor activities of orally administered agents were also assessed in CWR22Rv1 tumor-bearing mice. We demonstrated that Gal and NGGAs degraded AR/AR-V7 and Mnk1/2; blocked cell cycle progression and proliferation of human PC cells; induced apoptosis; inhibited cell migration, invasion, and putative stem cell markers; and reversed the expression of epithelial-to-mesenchymal transition (EMT). In addition, Gal/NGGAs (alone or in combination) also inhibited the growth of ENZ-, docetaxel-, and mitoxantrone-resistant human PC cell lines. The NGGAs exhibited improved pharmacokinetic profiles over Gal in mice. Importantly, in vivo testing showed that VNPP433-3ß (at 7.53-fold lower equimolar dose than Gal) markedly suppressed (84% vs. Gal, 47%; p < 0.01) the growth of castration-resistant PC (CRPC) CWR22Rv1 xenograft tumors, with no apparent host toxicity. ENZ was ineffective in this CRPC xenograft model. In summary, our findings show that targeting AR/AR-V7 and Mnk1/2 for degradation represents an effective therapeutic strategy for PC/CRPC treatment and supports further development of VNPP433-3ß towards clinical investigation.

The Novel Mnk1/2 Degrader and Apoptosis Inducer VNLG-152 Potently Inhibits TNBC Tumor Growth and Metastasis.

Currently, there are no effective therapies for patients with triple-negative breast cancer (TNBC), an aggressive and highly metastatic disease. Activation of eukaryotic initiation factor 4E (eIF4E) by mitogen-activated protein kinase (MAPK)-interacting kinases 1 and 2 (Mnk1/2) play a critical role in the development, progression and metastasis of TNBC. Herein, we undertook a comprehensive study to evaluate the activity of a first-in-class Mnk1/2 protein degraders, racemic VNLG-152R and its two enantiomers (VNLG-152E1 and VNLG-152E2) in in vitro and in vivo models of TNBC. These studies enabled us to identify racemic VNLG-152R as the most efficacious Mnk1/2 degrader, superior to its pure enantiomers. By targeting Mnk1/2 protein degradation (activity), VNLG-152R potently inhibited both Mnk-eIF4E and mTORC1 signaling pathways and strongly regulated downstream factors involved in cell cycle regulation, apoptosis, pro-inflammatory cytokines/chemokines secretion, epithelial-mesenchymal transition (EMT) and metastasis. Most importantly, orally bioavailable VNLG-152R exhibited remarkable antitumor (91 to 100% growth inhibition) and antimetastatic (~80% inhibition) activities against cell line and patient-derived TNBC xenograft models, with no apparent host toxicity. Collectively, these studies demonstrate that targeting Mnk-eIF4E/mTORC1 signaling with a potent Mnk1/2 degrader, VNLG-152R, is a novel therapeutic strategy that can be developed as monotherapy for the effective treatment of patients with primary/metastatic TNBC.

The retinamide VNLG-152 inhibits f-AR/AR-V7 and MNK-eIF4E signaling pathways to suppress EMT and castration-resistant prostate cancer xenograft growth.

VNLG-152 is a novel retinamide (NR) shown to suppress growth and progression of genetically diverse prostate cancer cells via inhibition of androgen receptor signaling and eukaryotic initiation factor 4E (eIF4E) translational machinery. Herein, we report therapeutic effects of VNLG-152 on castration-resistant prostate cancer (CRPC) growth and metastatic phenotype in a CRPC tumor xenograft model. Administration of VNLG-152 significantly and dose-dependently suppressed the growth of aggressive CWR22Rv1 tumors by 63.4% and 76.3% at 10 and 20 mg·kg-1 bw, respectively (P < 0.0001), vs. vehicle with no host toxicity. Strikingly, the expression of full-length androgen receptor (f-AR)/androgen receptor splice variant-7 (AR-V7), mitogen-activated protein kinase-interacting kinases 1 and 2 (MNK1/2), phosphorylated eIF4E and their associated target proteins, including prostate-specific antigen, cyclin D1 and Bcl-2, were strongly decreased in VNLG-152-treated tumors signifying inhibition of f-AR/AR-V7 and MNK-eIF4E signaling in VNLG-152-treated CWR22Rv1 tumors as observed in vitro. VNLG-152 also suppressed the epithelial to mesenchymal transition in CWR22Rv1 tumors as evidenced by repression of N-cadherin, ß-catenin, claudin, Slug, Snail, Twist, vimentin and matrix metalloproteinases (MMP-2 and MMP-9) with upsurge in E-cadherin. These results highlight the promising use of VNLG-152 in CRPC therapy and justify its further development towards clinical trials.

Galeterone and its analogs inhibit Mnk-eIF4E axis, synergize with gemcitabine, impede pancreatic cancer cell migration, invasion and proliferation and inhibit tumor growth in mice.

Survival rate for pancreatic cancer (pancreatic ductal adenocarcinoma, PDAC) is poor, with about 80% of patients presenting with the metastatic disease. Gemcitabine, the standard chemotherapeutic agent for locally advanced and metastatic PDAC has limited efficacy, attributed to innate/acquired resistance and activation of pro-survival pathways. The Mnk1/2-eIF4E and NF-κB signaling pathways are implicated in PDAC disease progression/metastasis and also associated with gemcitabine-induced resistance in PDAC. Galeterone (gal), a multi-target, agent in phase III clinical development for prostate cancer has also shown effects on the aforementioned pathways. We show for the first time, that gal/analogs (VNPT55, VNPP414 and VNPP433-3ß) profoundly inhibited cell viability of gemcitabine-naive/resistance PDAC cell lines and strongly synergized with gemcitabine in gemcitabine-resistant PDAC cells. In addition, to inducing G1 cell cycle arrest, gal/analogs induced caspase 3-mediated cell-death of PDAC cells. Gal/analogs caused profound downregulation of Mnk1/2, peIF4E and NF-κB (p-p65), metastatic inducing factors (N-cadherin, MMP-1/-2/-9, Slug, Snail and CXCR4) and putative stem cell factors, (ß-Catenin, Nanog, BMI-1 and Oct-4). Gal/analog also depleted EZH2 and upregulated E-Cadherin. These effects resulted in significant inhibition of PDAC cell migration, invasion and proliferation. Importantly, we also observed strong MiaPaca-2 tumor xenograft growth inhibition (61% to 92%). Collectively, these promising findings strongly support further development of gal/analogs as novel therapeutics for PDAC.

Targeting of protein translation as a new treatment paradigm for prostate cancer.

PURPOSE OF REVIEW: The current overview will summarize some of the developments in the area of protein translation, including their relation to the therapeutic targeting of prostate cancer. RECENT FINDINGS: Translational control, mediated by the rate-limiting eukaryotic translation initiation factor 4E (eIF4E), drives selective translation of several oncogenic proteins, thereby contributing to tumor growth, metastasis, and treatment resistance in various cancers, including prostate cancer. As an essential regulatory hub, several oncogenic hyperactive signaling pathways appear to converge on eIF4E to promote tumorigenesis. Several approaches that target the eIF4E-dependent protein translation network are being actively studied, and it is likely that some may ultimately emerge as promising anticancer therapeutics. SUMMARY: An array of inhibitors has shown promise in targeting specific components of the translational machinery in several preclinical models of prostate cancer. It is hoped that some of these approaches may ultimately have relevance in improving the clinical outcomes of patients with advanced prostate cancer.

Dissecting major signaling pathways in prostate cancer development and progression: Mechanisms and novel therapeutic targets.

Prostate cancer (PCa) is the most frequently diagnosed non-cutaneous malignancy and leading cause of cancer mortality in men. At the initial stages, prostate cancer is dependent upon androgens for their growth and hence effectively combated by androgen deprivation therapy (ADT). However, most patients eventually recur with an androgen deprivation-resistant phenotype, referred to as castration-resistant prostate cancer (CRPC), a more aggressive form for which there is no effective therapy presently available. The current review is an attempt to cover and establish an understanding of some major signaling pathways implicated in prostate cancer development and castration-resistance, besides addressing therapeutic strategies that targets the key signaling mechanisms.

Identification of Novel Steroidal Androgen Receptor Degrading Agents Inspired by Galeterone 3ß-Imidazole Carbamate.

Degradation of all forms of androgen receptors (ARs) is emerging as an advantageous therapeutic paradigm for the effective treatment of prostate cancer. In continuation of our program to identify and develop improved efficacious novel small-molecule agents designed to disrupt AR signaling through enhanced AR degradation, we have designed, synthesized, and evaluated novel C-3 modified analogues of our phase 3 clinical agent, galeterone (5). Concerns of potential in vivo stability of our recently discovered more efficacious galeterone 3ß-imidazole carbamate (6) led to the design and synthesis of new steroidal compounds. Two of the 11 compounds, 3ß-pyridyl ether (8) and 3ß-imidazole (17) with antiproliferative GI50 values of 3.24 and 2.54 µM against CWR22Rv1 prostate cancer cell, are 2.75- and 3.5-fold superior to 5. In addition, compounds 8 and 17 possess improved (∼4-fold) AR-V7 degrading activities. Importantly, these two compounds are expected to be metabolically stable, making them suitable for further development as new therapeutics against all forms of prostate cancer.

Galeterone and VNPT55 induce proteasomal degradation of AR/AR-V7, induce significant apoptosis via cytochrome c release and suppress growth of castration resistant prostate cancer xenografts in vivo.

Galeterone (Gal) is a first-in-class multi-target oral small molecule that will soon enter pivotal phase III clinical trials in castration resistant prostate cancer (CRPC) patients. Gal disrupts androgen receptor (AR) signaling via inhibition of CYP17, AR antagonism and AR degradation. Resistance to current therapy is attributed to up-regulation of full-length AR (fAR), splice variants AR (AR-Vs) and AR mutations. The effects of gal and VNPT55 were analyzed on f-AR and AR-Vs (AR-V7/ARv567es) in LNCaP, CWR22Rv1 and DU145 (transfected with AR-Vs) human PC cells in vitro and CRPC tumor xenografts. Galeterone/VNPT55 decreased fAR/AR-V7 mRNA levels and implicates Mdm2/CHIP enhanced ubiquitination of posttranslational modified receptors, targeting them for proteasomal degradation. Gal and VNPT55 also induced significant apoptosis in PC cells via increased Bax/Bcl2 ratio, cytochrome-c release with concomitant cleavage of caspase 3 and PARP. More importantly, gal and VNPT55 exhibited strong in vivo anti-CRPC activities, with no apparent host toxicities. This study demonstrate that gal and VNPT55 utilize cell-based mechanisms to deplete both fAR and AR-Vs. Importantly, the preclinical activity profiles, including profound apoptotic induction and inhibition of CRPC xenografts suggest that these agents offer considerable promise as new therapeutics for patients with CRPC and those resistant to current therapy.

Novel C-4 heteroaryl 13-cis-retinamide Mnk/AR degrading agents inhibit cell proliferation and migration and induce apoptosis in human breast and prostate cancer cells and suppress growth of MDA-MB-231 human breast and CWR22Rv1 human prostate tumor xenografts in mice.

The synthesis and in vitro and in vivo antibreast and antiprostate cancers activities of novel C-4 heteroaryl 13-cis-retinamides that modulate Mnk-eIF4E and AR signaling are discussed. Modifications of the C-4 heteroaryl substituents reveal that the 1H-imidazole is essential for high anticancer activity. The most potent compounds against a variety of human breast and prostate cancer (BC/PC) cell lines were compounds 16 (VNHM-1-66), 20 (VNHM-1-81), and 22 (VNHM-1-73). In these cell lines, the compounds induce Mnk1/2 degradation to substantially suppress eIF4E phosphorylation. In PC cells, the compounds induce degradation of both full-length androgen receptor (fAR) and splice variant AR (AR-V7) to inhibit AR transcriptional activity. More importantly, VNHM-1-81 has strong in vivo antibreast and antiprostate cancer activities, while VNHM-1-73 exhibited strong in vivo antibreast cancer activity, with no apparent host toxicity. Clearly, these lead compounds are strong candidates for development for the treatments of human breast and prostate cancers.

Simultaneous targeting of androgen receptor (AR) and MAPK-interacting kinases (MNKs) by novel retinamides inhibits growth of human prostate cancer cell lines.

Androgen receptor (AR) and MNK activated eIF4E signaling promotes the development and progression of prostate cancer (PCa). In this study, we report that our Novel Retinamides (NRs) target both AR signaling and eIF4E translation in androgen sensitive and castration resistant PCa cells via enhancing AR and MNK degradation through ubiquitin-proteasome pathway. Dual blockade of AR and MNK initiated eIF4E activation by NRs in turn induced cell cycle arrest, apoptosis, and inhibited cell proliferation. NRs also inhibited cell migration and invasion in metastatic cells. Importantly, the inhibitory effects of NRs on AR signaling, eIF4E translation initiation and subsequent oncogenic program were more potent than that observed with clinically relevant retinoids, established MNK inhibitors, and the FDA approved PCa drugs. Our findings provide the first preclinical evidence that simultaneous inhibition of AR and eIF4E activation is a novel and efficacious therapeutic approach for PCa, and that NRs hold significant promise for treatment of advanced prostate cancer.

VN/14-1 induces ER stress and autophagy in HP-LTLC human breast cancer cells and has excellent oral pharmacokinetic profile in female Sprague Dawley rats.

Resistance to aromatase inhibitors is a major concern in the treatment of breast cancer. Long-term letrozole cultured (LTLC) cells represent a model of resistance to aromatase inhibitors. The LTLC cells were earlier generated by culturing MCF-7Ca, the MCF-7 human breast cancer cell line stably transfected with human placental aromatase gene for a prolonged period in the presence of letrozole. In the present study the effect of RAMBA, VN/14-1 on the sensitivity of LTLC cells upon multiple passaging and the mechanisms of action of VN/14-1 in such high passage LTLC (HP-LTLC) cells was investigated. We report that multiple passaging of LTLC cells (HP-LTLC cell clones) led to profound decrease in their sensitivity to VN/14-1. Additionally, microarray studies and protein analysis revealed that VN/14-1 induced marked endoplasmic reticulum (ER) stress and autophagy in HP-LTLC cells. We further report that VN/14-1 in combination with thapsigargin exhibited synergistic anti-cancer effect in HP-LTLC cells. Preliminary pharmacokinetics in rats revealed that VN/14-1 reached a peak plasma concentration (Cmax) within 0.17h after oral dosing. Its absolute oral bioavailability was >100%. Overall these results indicate potential of VN/14-1 for further clinical development as a potential oral agent for the treatment of breast cancer.

First MNKs degrading agents block phosphorylation of eIF4E, induce apoptosis, inhibit cell growth, migration and invasion in triple negative and Her2-overexpressing breast cancer cell lines.

Some retinoic acid metabolism blocking agents (RAMBAs) are known to exhibit a wide range of anticancer activities by mechanisms that are still not completely resolved. This study investigated the anticancer efficacy and mechanism(s) of novel RAMBA retinamides (RRs) in triple negative and Her-2 overexpressing breast cancer cells. Specifically, we examined the possibility that RRs affect the translational machinery in these breast cancer (BC) cells. Recent findings suggest that overexpression of eukaryotic translation initiation factor 4E (eIF4E) in breast cancers critically augments CAP-dependent mRNA translation and synthesis of proteins involved in cell growth, cell proliferation, invasion and apoptosis evasion. The oncogenic potential of eIF4E is strictly dependent on serine209 phosphorylation by upstream MAPK-interacting kinases (Mnks). Targeting Mnk/eIF4E pathway for blocking Mnk function and eIF4E phosphorylation is therefore a novel approach for treating BCs, particularly for Her2-positive and triple negative breast cancers that have no indications for endocrine therapy or effective treatment regimes. We report for the first time that the degradation of Mnk1 by RRs in BC cells blocks eIF4E phosphorylation and subsequently inhibits cell growth, colonization, invasion, and migration and induce apoptosis. Most importantly, the anticancer efficacy of RRs was mediated via degrading Mnk rather than inhibiting its kinase activity like Mnk inhibitors (cercosporamide and CGP57380). Furthermore, RRs potencies on peIF4E down-regulation and growth inhibition were superior to those of two clinically relevant retinoids and the Mnk inhibitors. Together our findings provide the first preclinical proof-of-concept of novel Mnk degrading agents for Mnk/eIF4E based therapeutic treatment of breast cancers.