Potential Clinical Uses of CDK Inhibitors: Lessons from Synthetic Lethality Screens

Discovery of quinazoline derivatives as a novel class of potent and in vivo efficacious LSD1 inhibitors by drug repurposing

Histone lysine-specific demethylase 1 (LSD1) is an important epigenetic modulator, and is implicated in malignant transformation and tumor pathogenesis in different ways. Therefore, the inhibition of LSD1 provides an attractive therapeutic target for cancer therapy. Based on drug repurposing strategy, we screened our in-house chemical library toward LSD1, and found that the EGFR inhibitor erlotinib, an FDA-approved drug for lung cancer, possessed low potency against LSD1 (IC₅₀ = 35.80 μM). Herein, we report our further medicinal chemistry effort to obtain a highly water-soluble erlotinib analog 5k (>100 mg/mL) with significantly enhanced inhibitory activity against LSD1 (IC₅₀ = 0.69 μM) as well as higher specificity. In MGC-803 cells, 5k suppressed the demethylation of LSD1, indicating its cellular activity against the enzyme. In addition, 5k had a remarkable capacity to inhibit colony formation, suppress migration and induce apoptosis of MGC803 cells. Furthermore, in MGC-803 xenograft mouse model, 5k treatment resulted in significant reduction in tumor size by 81.6% and 96.1% at dosages of 40 and 80 mg/kg/d, respectively. Our findings indicate that erlotinib-based analogs provide a novel structural set of LSD1 inhibitors with potential for further investigation, and may serve as novel candidates for the treatment of LSD1-overexpressing cancers.

miR-34c-3p targets CDK1 a synthetic lethality partner of KRAS in non-small cell lung cancer

Lung cancer is still the leading cause of death by cancer worldwide despite advances both in its detection and therapy. Multiple oncogenic driver alterations have been discovered, opening the prospective for new potential therapeutic targets. Among them, KRAS mutations represent the most frequent oncogene aberrations in non-small cell lung cancer (NSCLC) patients with a negative prognostic impact, but effective therapies targeting KRAS are not well characterized yet. Here, we demonstrate that the microRNA miR-34c-3p is a positive prognostic factor in KRAS-mutated NSCLC patients. Firstly, looking at the TGCA dataset, we found that high miR-34c-3p expression correlated with longer survival of KRAS-mutated NSCLC patients. In vitro assays on immortalized and patient-derived primary NSCLC cells revealed that miR-34c-3p overexpression increased apoptosis and lowered proliferation rate in KRASmut cells. Computational analysis and in vitro assays identified CDK1, one of the most promising lethal targets for KRAS-mutant cancer, as a target of miR-34c-3p. Moreover, the combination of CDK1 inhibition (mediated by RO3306) and miR-34c-3p overexpression resulted in an additive effect on the viability of KRASmut-expressing cells. Altogether, our findings demonstrate that miR-34c-3p is a novel biomarker that may allow tailored treatment for KRAS-mutated NSCLC patients.

Clinical Candidates Targeting the ATR-CHK1-WEE1 Axis in Cancer

Selective killing of cancer cells while sparing healthy ones is the principle of the perfect cancer treatment and the primary aim of many oncologists, molecular biologists, and medicinal chemists. To achieve this goal, it is crucial to understand the molecular mechanisms that distinguish cancer cells from healthy ones. Accordingly, several clinical candidates that use particular mutations in cell-cycle progressions have been developed to kill cancer cells. As the majority of cancer cells have defects in G1 control, targeting the subsequent intra‑S or G2/M checkpoints has also been extensively pursued. This review focuses on clinical candidates that target the kinases involved in intra‑S and G2/M checkpoints, namely, ATR, CHK1, and WEE1 inhibitors. It provides insight into their current status and future perspectives for anticancer treatment. Overall, even though CHK1 inhibitors are still far from clinical establishment, promising accomplishments with ATR and WEE1 inhibitors in phase II trials present a positive outlook for patient survival.

Overexpression of GSDMC is a prognostic factor for predicting a poor outcome in lung adenocarcinoma

The gasdermin (GSDM) superfamily has been demonstrated to consist of several important molecules that modulate multifunctional signal processes, such as cell pyroptosis. In this research, the roles of the GSDM superfamily on the occurrence and prognosis of lung adenocarcinoma (LUAD) were evaluated using integrative bioinformatic analyses and in vitro methods. Here, data from several bioinformatic platforms revealed that GSDMC is significantly upregulated in LUAD tissues and cell lines. Real-time fluorescence quantitative PCR (qPCR) demonstrated that GSDMC was obviously upregulated in radio-resistant LUAD cells, compared with their parental cells. Moreover, upregulated GSDMC expression was confirmed to be an independent indicator of poor first progression (FP) and overall survival (OS) in LUAD patients. DNA methylation analysis showed an evidently negative correlation between GSDMC expression and methylation status of one CpG site (cg05316065) in its DNA sequence. Patients with high methylation values had significantly higher Karnofsky performance scores (KPSs) and prolonged OS rates. Together, we confirmed that overexpression of GSDMC acts as a promising predictive factor for the poor prognosis of LUAD patients.

Development of the triazole-fused pyrimidine derivatives as highly potent and reversible inhibitors of histone lysine specific demethylase 1 (LSD1/KDM1A)

Histone lysine specific demethylase 1 (LSD1) has been recognized as an important modulator in post-translational process in epigenetics. Dysregulation of LSD1 has been implicated in the development of various cancers. Herein, we report the discovery of the hit compound 8a (IC₅₀ = 3.93 μmol/L) and further medicinal chemistry efforts, leading to the generation of compound 15u (IC₅₀ = 49 nmol/L, and K_i = 16 nmol/L), which inhibited LSD1 reversibly and competitively with H3K4me2, and was selective to LSD1 over MAO-A/B. Docking studies were performed to rationalize the potency of compound 15u. Compound 15u also showed strong antiproliferative activity against four leukemia cell lines (OCL-AML3, K562, THP-1 and U937) as well as the lymphoma cell line Raji with the IC₅₀ values of 1.79, 1.30, 0.45, 1.22 and 1.40 μmol/L, respectively. In THP-1 cell line, 15u significantly inhibited colony formation and caused remarkable morphological changes. Compound 15u induced expression of CD86 and CD11b in THP-1 cells, confirming its cellular activity and ability of inducing differentiation. The findings further indicate that targeting LSD1 is a promising strategy for AML treatment, the triazole-fused pyrimidine derivatives are new scaffolds for the development of LSD1/KDM1A inhibitors.

Bcl-xL inhibition enhances Dinaciclib-induced cell death in soft-tissue sarcomas

Soft-tissue sarcomas (STS) are an uncommon and heterogeneous group of malignancies that result in high mortality. Metastatic STS have very bad prognosis due to the lack of effective treatments. Dinaciclib is a model drug for the family of CDK inhibitors. Its main targets are cell cycle regulator CDK1 and protein synthesis controller CDK9. We present data supporting Dinaciclib ability to inactivate in vitro different STS models at nanomolar concentrations. Moreover, the different rhythms of cell death induction allow us to further study into the mechanism of action of the drug. Cell death was found to respond to the mitochondrial pathway of apoptosis. Anti-apoptotic Bcl-x_L was identified as the key regulator of this process. Already natural low levels of pro-apoptotic proteins BIM and PUMA in tolerant cell lines were insufficient to inhibit Bcl-x_L as this anti-apoptotic protein showed a slow decay curve after Dinaciclib-induced protein synthesis disruption. Combination of Dinaciclib with BH3-mimetics led to quick and massive apoptosis induction in vitro, but in vivo assessment was prevented due to liver toxicity. Additionally, Bcl-x_L inhibitor A-1331852 also synergized with conventional chemotherapy drugs as Gemcitabine. Thus, Bcl-x_L targeted therapy arises as a major opportunity to the treatment of STS.

New palbociclib analogues modified at the terminal piperazine ring and their anticancer activities

A series of new palbociclib analogs by extensive functionalization of the tail piperazine ring with various carbamates and amides have been synthesized. All the palbociclib derivatives were evaluated for their cytotoxic activities against MCF-7 cell line. From the anti-proliferation activity results, two of the tested compounds (compounds 4d and 4e) showed significant cytotoxic effects. And compounds 4d and 4e exhibited potent anticancer activities in MDA-MB-453 and MDA-MB-231 cells. Among these derivatives compound 4e was found to possess cytotoxicity that is better than standard drug palbociclib. Moreover, compound 4e demonstrated robust tumor growth inhibition in vivo model.