Therapeutic inhibition of polo-like kinases in anaplastic thyroid cancer

Vincristine/Volasertib Polymersome Injection Enables High-Efficiency Synergistic Treatment of Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia (ALL), one of the most frequently diagnosed malignancies in children, is associated with a high relapse rate and drug resistance, even with intensive multidrug chemotherapy regimens. The rational combination with molecular targeted agents holds promise for sensitizing patients to chemotherapies and overcoming drug resistance. However, precise codelivery of different drugs in vivo is challenging, often leading to suboptimal therapeutic effects. Herein, we report a vincristine/volasertib polymersome (Ps-VCR/Vol)-based nanocombo for synergistic inhibition of microtubules and polo-like kinase 1, enabling high-efficacy treatment of ALL in vivo. Ps-VCR/Vol, which has a small size (∼26 nm) and tailored VCR/Vol mass ratios from 1:12 to 1:48, exhibited strong synergy in different ALL cells, with 3.3-6.8-fold greater anti-ALL activity than the free VCR/Vol combination. Intriguingly, treatment with Ps-VCR/Vol at a VCR/Vol dosage of 0.25/6 mg/kg markedly inhibited leukemia progression and invasion in orthotopic CCRF-CEM, Nalm-6-Luc and patient-derived xenograft ALL mouse models without inducing toxicity, resulting in a significantly prolonged survival time compared with that of the free drug combination and single-drug polymersome formulations. Ps-VCR/Vol polymersome injection provides a powerful synergistic combination therapy for ALL. STATEMENT OF SIGNIFICANCE: Multidrug combination therapies have increased the remission rates of acute lymphoblastic leukemia (ALL) patients. However, the therapeutic efficacy remains suboptimal due to the dissimilar physicochemical properties of the different drugs involved, and overlapping toxicities pose a critical concern. Herein, we show that intelligent polymersomes mediate the precise codelivery of vincristine sulfate (VCR), a frontline drug for ALL, and volasertib (Vol), a polo-like kinase 1 inhibitor, enabling synergistic treatment of ALL. Compared with free VCR/Vol, VCR/Vol polymersomes with tailored drug ratios substantially inhibited leukemia progression in both cell line- and patient-derived orthotopic ALL models without inducing toxicity, leading to a significant survival benefit. This synergistic polymersome injection may provide a powerful and safe combination therapy for ALL patients.

PLK4 inhibitor exhibits antitumor effect and synergizes sorafenib via arresting cell cycle and inactivating Wnt/β-catenin pathway in anaplastic thyroid cancer

The anti-tumor effect of polo-like kinase 4 (PLK4) inhibitor has been explored in several solid carcinomas, while its application in anaplastic thyroid cancer (ATC) remains scarce. Hence, the current study aimed to investigate the effect of PLK4 inhibitor on the malignant behaviors of ATC cell lines and its synergistic antitumor effect with sorafenib. C643 and 8305c cells were cultured in various concentrations of centrinone (PLK4 inhibitor) with or without sorafenib. Meanwhile, the cell viability, cell apoptosis, cell cycle and expressions of glycogen synthetase kinase beta (GSK3β), p-GSK3β, β-catenin were determined. PLK4 mRNA and protein expressions were higher in most ATC cell lines than the normal thyroid epithelial cell line (all P < .05). Centrinone decreased cell viability, induced cell apoptosis, arrested cell cycle at G2/M phase and inactivated Wnt/β-catenin signaling with dose-dependent manners in C643 and 8305c cells (all P < .05). Interestingly, centrinone plus sorafenib further improved antitumor effect (P < .05 at most concentrations), with the highest combination index at 5 nM centrinone plus 4 μM sorafenib in C643 cells, then 4 nM centrinone plus 4 μM sorafenib in C643 cells. Subsequently, centrinone plus sorafenib reduced cell viability, promoted cell apoptosis, facilitated cell cycle at G2/M phase and repressed Wnt/β-catenin signaling more effectively compared with centrinone or sorafenib monotherapy in C643 and 8305c cells (all P < .05). PLK4 inhibitor exhibits antitumor effect and synergizes sorafenib via arresting cell cycle and inactivating Wnt/β-catenin pathway in ATC.

Comprehensive analysis of PLKs expression and prognosis in breast cancer

OBJECTIVE

A thorough examination of PLKs in breast cancer, including their expression and prognosis.

METHODS

With the help of the Oncomine database, the transcript levels of PLKs in breast cancer were examined. The changes in PLKs expression with tumor stage and indeed the relationship between PLKs expression and stage of cancer in women with breast cancer were scrutinized by using the GEPIA database. Based on Kaplan-Meier plots, breast cancer patients were assessed for their prognosis. Breast cancer gene expression and mutations were analyzed within the cBioPortal database.

RESULTS

According to Oncomine data, PLK1 and PLK4 mRNA expression levels were dramatically elevated in breast cancer patients while PLK2 and PLK5P levels were significantly downregulated. PLK1 and PLK4 expression were discovered to be greater in breast cancer tissues than in healthy tissues following analysis of the GEPIA database (P < 0.05). High levels of PLK1 and PLK4 transcripts have been linked to poor relapse-free survival rates across all patients with breast cancer according to the Kaplan-Meier Plotter database. The high levels of PLK2, PLK3, and PLK5 were associated with a higher recurrence-free survival rate. In the cBioPortal database, PLK was altered in 9.6% of breast cancer samples. Genetic alterations occurred in 15.07% of clinically counted invasive breast cancers, with mutations in 4.11%, gene amplifications in 9.59%, and gene deletion mutations in 1.37%. Additionally, the KEGG database demonstrates that PLKs are crucial for the cell cycle. The findings imply that elevated PLK1 and PLK4 expression in tissues of breast cancer might contribute significantly to the carcinogenesis of breast cancer. Moreover, PLK1 and PLK4 are highly expressed in breast cancer, and their use as molecular markers to identify high-risk subsets from patients with breast cancer is potentially possible.

CONCLUSIONS

For the precise therapy of breast cancers, PLK1 and PLK4 are potential targets, while PLK2, PLK3, and PLK5 are brand-new biomarkers for predicting the prognosis of breast cancer.

Polo-like kinase 1 (PLK1) signaling in cancer and beyond

PLK1 is an evolutionary conserved Ser/Thr kinase that is best known for its role in cell cycle regulation and is expressed predominantly during the G2/S and M phase of the cell cycle. PLK1-mediated phosphorylation of specific substrates controls cell entry into mitosis, centrosome maturation, spindle assembly, sister chromatid cohesion and cytokinesis. In addition, a growing body of evidence describes additional roles of PLK1 beyond the cell cycle, more specifically in the DNA damage response, autophagy, apoptosis and cytokine signaling. PLK1 has an indisputable role in cancer as it controls several key transcription factors and promotes cell proliferation, transformation and epithelial-to-mesenchymal transition. Furthermore, deregulation of PLK1 results in chromosome instability and aneuploidy. PLK1 is overexpressed in many cancers, which is associated with poor prognosis, making PLK1 an attractive target for cancer treatment. Additionally, PLK1 is involved in immune and neurological disorders including Graft versus Host Disease, Huntington's disease and Alzheimer's disease. Unfortunately, newly developed small compound PLK1 inhibitors have only had limited success so far, due to low therapeutic response rates and toxicity. In this review we will highlight the current knowledge about the established roles of PLK1 in mitosis regulation and beyond. In addition, we will discuss its tumor promoting but also tumor suppressing capacities, as well as the available PLK1 inhibitors, elaborating on their efficacy and limitations.

Therapeutic inhibition of polo-like kinases in anaplastic thyroid cancer

Polo‐like kinases (PLKs) are potent regulators of cell proliferation and cell survival. Polo‐like kinases are potential targets in the treatment of anaplastic thyroid cancer (ATC), a rare but deadly disease. The therapeutic effects of volasertib, a PLK inhibitor, was evaluated for the treatment of ATC either alone or in combination with sorafenib. Volasertib decreased cell viability in three ATC cell lines (8505C, 8305C, and KAT18) in a dose‐dependent manner. Volasertib caused ATC cells to accumulate in G₂/M phase, activated caspase‐3 activity, and induced apoptosis. Combination therapy using volasertib and sorafenib in ATC cells showed mostly synergistic effects. In vivo studies revealed that combination therapy of volasertib and sorafenib was effective in the treatment of 8505C xenografts. Single‐agent volasertib treatment was sufficient to retard 8305C tumor growth. No substantial morbidity was observed in animals that received either single‐agent or combination treatment. These preclinical findings suggest that volasertib could be an effective drug in treating ATC.