Growth arrest and apoptosis induced by kinesin Eg5 inhibitor K858 and by its 1,3,4-thiadiazoline analogue in tumor cells

Cancer on motors: How kinesins drive prostate cancer progression?

Prostate cancer causes numerous male deaths annually. Although great progress has been made in the diagnosis and treatment of prostate cancer during the past several decades, much about this disease remains unknown, especially its pathobiology. The kinesin superfamily is a pivotal group of motor proteins, that contains a microtubule-based motor domain and features an adenosine triphosphatase activity and motility characteristics. Large-scale sequencing analyses based on clinical samples and animal models have shown that several members of the kinesin family are dysregulated in prostate cancer. Abnormal expression of kinesins could be linked to uncontrolled cell growth, inhibited apoptosis and increased metastasis ability. Additionally, kinesins may be implicated in chemotherapy resistance and escape immunologic cytotoxicity, which creates a barrier to cancer treatment. Here we cover the recent advances in understanding how kinesins may drive prostate cancer progression and how targeting their function may be a therapeutic strategy. A better understanding of kinesins in prostate cancer tumorigenesis may be pivotal for improving disease outcomes in prostate cancer patients.

Kinesin Eg5 Selective Inhibition by Newly Synthesized Molecules as an Alternative Approach to Counteract Breast Cancer Progression: An In Vitro Study

Breast cancer (BC) is one of the most diagnosed cancers in women. Recently, a promising target for BC treatment was found in kinesin Eg5, a mitotic motor protein that allows bipolar spindle formation and cell replication. Thus, the aim of this work was to evaluate the effects of novel thiadiazoline-based Eg5 inhibitors, analogs of K858, in an in vitro model of BC (MCF7 cell line). Compounds 2 and 41 were selected for their better profile as they reduce MCF7 viability at lower concentrations and with minimal effect on non-tumoral cells with respect to K858. Compounds 2 and 41 counteract MCF7 migration by negatively modulating the NF-kB/MMP-9 pathway. The expression of HIF-1α and VEGF appeared also reduced by 2 and 41 administration, thus preventing the recruitment of the molecular cascade involved in angiogenesis promotion. In addition, 2 provokes an increased caspase-3 activation thus triggering the MCF7 apoptotic event, while 41 and K858 seem to induce the necrosis axis, as disclosed by the increased expression of PARP. These results allow us to argue that 2 and 41 are able to simultaneously intervene on pivotal molecular signaling involved in breast cancer progression, leading to the assumption that Eg5 inhibition can represent a valid approach to counteract BC progression.

TRAF4 Inhibits the Apoptosis and Promotes the Proliferation of Breast Cancer Cells by Inhibiting the Ubiquitination of Spindle Assembly-Associated Protein Eg5

Tumor necrosis factor receptor associated factor 4 (TRAF4) is a RING domain E3 ubiquitin ligase that mediates the ubiquitination of various proteins and plays an important role in driving tumor progression. By studying the relationship between TRAF4 and Eg5, a member of the kinesin family that plays a critical role in spindle assembly, we demonstrated that TRAF4 regulated Eg5 ubiquitination and contributed to Eg5-mediated breast cancer proliferation and inhibited breast cancer apoptosis. TRAF4 and Eg5 were both highly expressed in breast cancer and their protein level was positively correlated. Relying on its Zinc fingers domain, TRAF4 interacted with Eg5 in the cytoplasm of breast cancer cells. TRAF4 was a mitosis-related protein, and by up-regulating the protein level of Eg5 TRAF4 participated in spindle assembly. Loss of TRAF4 resulted in monopolar spindles formation, but loss of function could be rescued by Eg5. Relying on its RING domain, TRAF4 up-regulated Eg5 protein levels by inhibition of Eg5 ubiquitination, thus stabilizing Eg5 protein level during mitosis. Furthermore, we found that Smurf2, a TRAF4-targeted ubiquitination substrate, mediated the regulation of Eg5 ubiquitination by TRAF4. TRAF4 inhibited the interaction between Smurf2 and Eg5, and down-regulated the protein level of Smurf2 by promoting its ubiquitination, thereby inhibited the Smurf2-catalyzed ubiquitination of Eg5 and up-regulated Eg5 protein levels. We also demonstrate that TRAF4 plays an important role in promoting cell proliferation and in inhibiting cell apoptosis induced by Eg5. In summary, our study suggests a new direction for investigating the role of TRAF4 in driving breast cancer progression.

Eg5 as a Prognostic Biomarker and Potential Therapeutic Target for Hepatocellular Carcinoma

BACKGROUND

The kinesin Eg5, a mitosis-associated protein, is overexpressed in many cancers. Here we explored the clinical significance of Eg5 in hepatocellular carcinoma (HCC).

METHODS

HCC tissues from surgical resection were collected. Total RNA was prepared from tumorous and nontumorous parts. Eg5 expression levels were correlated with overall survival (OS) and disease-free survival (DFS). In vitro efficacy of LGI-147, a specific Eg5 inhibitor, was tested in HCC cell lines. In vivo efficacy of Eg5 inhibition was investigated in a xenograft model.

RESULTS

A total of 108 HCC samples were included. The patients were divided into three tertile groups with high, medium, and low Eg5 expression levels. OS of patients with low Eg5 expression was better than that of patients with medium and high Eg5 expression (median, 155.6 vs. 75.3 vs. 57.7 months, p = 0.002). DFS of patients with low Eg5 expression was also better than that of patients with medium and high Eg5 expression (median, 126.3 vs. 46.2 vs. 39.4 months, p = 0.001). In multivariate analyses, the associations between Eg5 expression and OS (p < 0.001) or DFS remained (p < 0.001). LGI-147 reduced cell growth via cell cycle arrest and apoptosis and induced accumulation of abnormal mitotic cells. In the xenograft model, the tumor growth rate under LGI-147 treatment was significantly slower than under the control.

CONCLUSION

High Eg5 expression was associated with poor HCC prognosis. In vitro and in vivo evidence suggests that Eg5 may be a reasonable therapeutic target for HCC.

Alkaloids isolated from Tropaeolum tuberosum with cytotoxic activity and apoptotic capacity in tumour cell lines

Two alkaloids were isolated and identified for the first time in the black tubers of Tropaeolum tuberosum, collected from the Titicani-Taca, Ingavi province in La Paz, Bolivia. Their structures were elucidated by extensive NMR and MS spectroscopic analyses. The isolated compounds were evaluated for their cytotoxicity and apoptotic capacity against four human cancer cell lines. 2-Benzyl-3-thioxohexahydropyrrolo[1,2-c]imidazole-1-one (1) showed slight cytotoxic activity against all the cancer cell lines which were tested, with IC₅₀ values ranging from 27.45 ± 0.80 to 31.07 ± 0.87 μM. Moreover, N-(4-acetyl-5-methyl-5-phenyl-4,5-dihydro-1,3,4-thiadiazol-2-yl) acetamide (2) showed significant anti-cancer potential, with IC₅₀ values between 1.26 ± 0.57 μM and 1.37 ± 0.09 μM against all human cancer cell lines which were tested. Treatment of tumour cell lines with the compounds caused an increase in the apoptotic rate of these cells, observing that compound 2 presented an apoptotic effect which was double with respect to the control (Dimethylenastron).

Kinesin Eg5 Targeting Inhibitors as a New Strategy for Gastric Adenocarcinoma Treatment

The Kinesins are proteins involved in several biological processes such as mitosis, intracellular transport, and microtubule movement. The mitotic process is allowed by the correct formation of the mitotic spindle which consists of microtubules originating from the spindle poles. In recent years, kinesin Eg5 inhibitors were studied as new chemotherapeutic drugs, due to the lack of side effects and resistance mechanisms. The aim of this work was to investigate the molecular signaling underlying the administration of novel kinesis Eg5 inhibitors in an in vitro model of gastric adenocarcinoma. Data obtained from analogues of K858 led us to select compounds 2 and 41, due to their lower IC₅₀ values. The ability of kinesin inhibitors to induce apoptosis was investigated by evaluating Bax and Caspase-3 protein expression, evidencing that compound 41 and K858 markedly raise Bax expression, while only compounds 2 and 41 co-administrated with K858 trigger Caspase-3 activation. The inhibition of mitotic spindle was measured by β-tubulin immunofluorescence analysis revealing monopolar spindles formation in gastric cancer cells treated with compounds 2, 41, and K858. Nitric Oxide Synthase (NOS-2) and Matrix Metalloproteinase 9 (MMP-9) expression levels were measured finding a NOS-2-mediated downregulation of MMP-9 when compound 41 and K858 are co-administered. However, this is in contrast to what was reported by migration assay in which both novel compounds and K858 in monotherapy markedly reduce cell migration. This work remarks the importance of understanding and exploring the biological effects of different novel Eg5 kinesin inhibitors administered in monotherapy and in combination with K858 as potential strategy to counteract gastric cancer.