Degradation of Polo-like Kinase 1 by the Novel Poly-Arginine N-Degron Pathway PROTAC Regulates Tumor Growth in Nonsmall Cell Lung Cancer

Polo-like kinase 1 (PLK1), which is crucial in cell cycle regulation, is considered a promising anticancer drug target. Herein, we present the N-degron pathway-based proteolysis targeting chimera (PROTAC) for PLK1 degradation, targeting the Polo-box domain (PBD). We identified DD-2 as the most potent PROTAC that selectively induces PLK1 degradation in cancer cells, including HeLa and nonsmall cell lung cancer (NSCLC), through the N-degron pathway. DD-2 exhibited significant in vitro anticancer effects, inducing G2/M arrest and apoptosis in HeLa and NSCLC cell lines. DD-2 showed significant tumor growth inhibition in a xenograft mouse model using HeLa and NSCLC cell lines, highlighting its potential in cancer treatment. Furthermore, the combination of DD-2 with tyrosine kinase inhibitor (TKI), osimertinib, effectively suppressed tumor growth in double-mutated H1975 cell lines, emphasizing DD-2's potential in combination cancer therapies. Collectively, this study demonstrates the potential of the N-degron pathway, especially using DD-2, for targeted cancer therapies.

An investigation of Plk1 PBD inhibitor KBJK557 as a tumor growth suppressor in non-small cell lung cancer

Lung cancer is the second most commonly reported type of cancer worldwide. Approximately 80–85% of lung cancer occurrences are accounted by non-small cell lung cancer (NSCLC). Polo-like kinase-1 (Plk1) plays multiple roles in cell cycle progression and its overexpression is observed in majority of malignancies, including NSCLC. A combination of frontline drugs and inhibitors targeting the Plk kinase domain (KD) has been used to overcome drug resistance in NSCLC. Plk1 KD inhibitors are highly prone to cross-reactivity with similar kinases, eventually leading to undesirable side effects. Moreover, there have been no reports of Plk1 PBD inhibitors showing antitumorigenic effects on NSCLC cells or animal models so far. To address this issue herein, for the first time, our recently reported Plk1 PBD inhibitor KBJK557 was evaluated for the anticancer potential against NSCLC cells. KBJK557 displayed notable cytotoxic effects in A549, PC9, and H1975 cells. Mechanistic investigations revealed that KBJK557-treated cells underwent G2/M cell cycle arrest, triggering subsequent apoptosis. In vivo antitumorigenic activity in xenograft mice model demonstrates that KBJK557-treated mice showed a considerable decrease in tumor size, proving the significances of Plk1 in lung cancer. Collectively, this study demonstrates that KBJK557 can serve as a promising drug candidate for treating the lung cancer through Plk1 PBD inhibition.

Amphipathic Small Molecule AZT Compound Displays Potent Inhibitory Effects in Cancer Cell Proliferation

Cancer has been identified as a leading cause of death worldwide, and the increasing number of cancer cases threatens to shorten the average life expectancy of people. Recently, we reported a 3-azido-3-deoxythymidine (AZT)-based amphipathic small molecule, ADG-2e that revealed a notable potency against tumor metastasis. To evaluate the anticancer potential of ADG-2e, we assessed its anticancer potency in vitro and in vivo. Anticancer screening of ADG-2e against cervical cancer cells, HeLa CCL2, and BT549 mammary gland ductal carcinoma showed significant inhibition of cancer cell proliferation. Furthermore, mechanistic investigations revealed that cancer cell death presumably proceeded through an oncosis mechanistic pathway because ADG-2e treated cells showed severe damage on the plasma membrane, a loss of membrane integrity, and leakage of α-tubulin and β-actin. Finally, evaluation of the antitumorigenic potential of ADG-2e in mouse xenograft models revealed that this compound potentially inhibits cancer cell proliferation. Collectively, these findings suggest that ADG-2e can evolve as an anticancer agent, which may represent a model for nucleoside-based small molecule anticancer drug discovery.