Aurora-a contributes to radioresistance by increasing NF-kappaB DNA binding

Targeting mitotic regulators in cancer as a strategy to enhance immune recognition

Eukaryotic DNA has evolved to be enclosed within the nucleus to protect the cellular genome from autoinflammatory responses driven by the immunogenic nature of cytoplasmic DNA. Cyclic GMP-AMP Synthase (cGAS) is the cytoplasmic dsDNA sensor, which upon activation of Stimulator of Interferon Genes (STING), mediates production of pro-inflammatory interferons (IFNs) and interferon stimulated genes (ISGs). However, although this pathway is crucial in detection of viral and microbial genetic material, cytoplasmic DNA is not always of foreign origin. It is now recognised that specifically in genomic instability, a hallmark of cancer, extranuclear material in the form of micronuclei (MN) can be generated as a result of unresolved DNA lesions during mitosis. Activation of cGAS-STING in cancer has been shown to regulate numerous tumour-immune interactions such as acquisition of 'immunologically hot' phenotype which stimulates immune-mediated elimination of transformed cells. Nonetheless, a significant percentage of poorly prognostic cancers is 'immunologically cold'. As this state has been linked with low proportion of tumour-infiltrating lymphocytes (TILs), improving immunogenicity of cold tumours could be clinically relevant by exhibiting synergy with immunotherapy. This review aims to present how inhibition of vital mitotic regulators could provoke cGAS-STING response in cancer and improve the efficacy of current immunotherapy regimens.

A phase I dose escalation, dose expansion and pharmacokinetic trial of gemcitabine and alisertib in advanced solid tumors and pancreatic cancer

PURPOSE

Aurora Kinase A (AKA) inhibition with gemcitabine represents a potentially synergistic cancer treatment strategy via mitotic catastrophe. The feasibility, safety, and preliminary efficacy of alisertib (MLN8237), an oral AKA inhibitor, with gemcitabine was evaluated in this open-label phase I trial with dose escalation and expansion.

METHODS

Key inclusion criteria included advanced solid tumor with any number of prior chemotherapy regimens in the dose escalation phase, and advanced pancreatic adenocarcinoma with up to two prior chemotherapy regimens. Four dose levels (DLs 1-4) of alisertib (20, 30, 40, or 50 mg) were evaluated in 3 + 3 design with gemcitabine 1000 mg/m² on days 1, 8, and 15 in 28-day cycles.

RESULTS

In total, 21 subjects were treated in dose escalation and 5 subjects were treated in dose expansion at DL4. Dose-limiting toxicities were observed in 1 of 6 subjects each in DL3 and DL4. All subjects experienced treatment-related adverse events. Grade ≥ 3 treatment-related adverse events were observed in 73% of subjects, with neutropenia observed in 54%. Out of 22 subjects evaluable for response, 2 subjects (9%) had partial response and 14 subjects (64%) had stable disease. Median PFS was 4.1 months (95% CI 2.1-4.5). No significant changes in pharmacokinetic parameters for gemcitabine or its metabolite dFdU were observed with alisertib co-administration.

CONCLUSIONS

This trial established the recommended phase 2 dose of alisertib 50 mg to be combined with gemcitabine. Gemcitabine and alisertib are a feasible strategy with potential for disease control in multiple heavily pre-treated tumors, though gastrointestinal and hematologic toxicity was apparent.

Pharmacological Targeting of Cell Cycle, Apoptotic and Cell Adhesion Signaling Pathways Implicated in Chemoresistance of Cancer Cells

Chemotherapeutic drugs target a physiological differentiating feature of cancer cells as they tend to actively proliferate more than normal cells. They have well-known side-effects resulting from the death of highly proliferative normal cells in the gut and immune system. Cancer treatment has changed dramatically over the years owing to rapid advances in oncology research. Developments in cancer therapies, namely surgery, radiotherapy, cytotoxic chemotherapy and selective treatment methods due to better understanding of tumor characteristics, have significantly increased cancer survival. However, many chemotherapeutic regimes still fail, with 90% of the drug failures in metastatic cancer treatment due to chemoresistance, as cancer cells eventually develop resistance to chemotherapeutic drugs. Chemoresistance is caused through genetic mutations in various proteins involved in cellular mechanisms such as cell cycle, apoptosis and cell adhesion, and targeting those mechanisms could improve outcomes of cancer therapy. Recent developments in cancer treatment are focused on combination therapy, whereby cells are sensitized to chemotherapeutic agents using inhibitors of target pathways inducing chemoresistance thus, hopefully, overcoming the problems of drug resistance. In this review, we discuss the role of cell cycle, apoptosis and cell adhesion in cancer chemoresistance mechanisms, possible drugs to target these pathways and, thus, novel therapeutic approaches for cancer treatment.

Aurora-A affects radiosenstivity in cervical squamous cell carcinoma and predicts poor prognosis

BACKGROUND

Definitive radiation therapy (RT) (with or without cisplatin-based chemotherapy) is one of the most effective treatments for cervical squamous cell carcinoma (CSCC), but efficacy is limited due to resistance. In the present study, we investigated the relationship between the expression of Aurora kinase A (Aurora-A, AURKA)and response to RT in patients with CSCC.

METHODS

The expression of Aurora-A in biopsy specimens of untreated primary tumors in 129 Uyghur patients with CSCC was investigated immunohistochemically. Primary treatment in these patients was definitive radical RT, which consisted of pelvic RT plus brachytherapy (total point A dose:70-85 Gy) (with or without cisplatin-based chemotherapy). The prognostic value of tumoral Aurora-A expression and patients' clinical outcomes were evaluated.

RESULTS

Aurora-A expression was significantly associated with lymph node metastasis (P<0.001), large tumor size (P<0.001), low hemoglobin (Hb) level (P=0.011) and recurrence (P<0.001), but not other clinicopathological factors. Definitive RT was unfavorable in patients with high Aurora-A expression (P < 0.001). In 129 enrolled patients, lymph node metastasis, large tumor size, low Hb level, and AURKA overexpression were prognostic factors for both recurrent free survival (RFS) and overall survival (OS) in univariate analysis. However, only high AURKA expression was an adverse independent risk factor for both RFS (hazard ratio, 3.953; 95% CI, 1.473-10.638; P = 0.006) and OS (hazard ratio 9.091; 95%CI 2.597-32.258; P<0.001) in multivariate analyses.

CONCLUSIONS

Aurora-A may serve as a predictive biomarker of radiation response and a therapeutic target to reverse radiation therapy resistance.

The p38 MAPK inhibitor BIRB796 enhances the antitumor effects of VX680 in cervical cancer

VX680 is a potent and selective inhibitor that targets the Aurora kinase family. The p38 mitogen-activated protein kinase (MAPK) regulates a large number of cellular pathways and plays an important role in the regulation of cell survival and apoptosis. This study aimed to evaluate the effect of VX680 on cervical cancer cells and investigate whether the effects on apoptosis are enhanced by the ablation of p38 MAPK activation. The results suggested that VX680 inhibited the proliferation of cervical cancer cells by causing G2/M phase arrest and endoreduplication and that the apoptotic effect was attenuated by the activation of p38 MAPK. However, the addition of BIRB796, which is an important p38 MAPK inhibitor, effectively eliminated the expression of p-p38 and hence significantly enhanced the cell death induced by VX680 in vitro. Further study demonstrated that BIRB796 cooperated with VX680 to suppress cervical cancer cell growth in a mouse xenograft model. Taken together, our results demonstrated that VX680 induced cell cycle arrest and endoreduplication in human cervical cancer cells. Combined treatment with VX680 and BIRB796 synergistically inhibited tumor growth both in vitro and in vivo. Dual blockade of Aurora kinases and p38 MAPK is therefore a promising strategy for cervical cancer treatment.

miR-668 enhances the radioresistance of human breast cancer cell by targeting IκBα

BACKGROUND

A large proportion of breast cancer patients are resistant to radiotherapy, which is a mainstay treatment for this malignancy, but the mechanisms of radioresistance remain unclear.

METHODS AND MATERIALS

To evaluate the role of miRNAs in radioresistance, we established two radioresistant breast cancer cell lines MCF-7R and T-47DR derived from parental MCF-7 and T-47D. Moreover, miRNA microarray, quantitative RT-PCR analysis, luciferase reporter assay and western blotting were used.

RESULTS

We found that miR-668 was most abundantly expressed in radioresistant cells MCF-7R and T-47DR. miR-668 knockdown reversed radioresistance of MCF-7R and T-47DR, miR-668 overexpression enhanced radioresistance of MCF-7 and T-47D cells. Mechanically, bioinformatics analysis combined with experimental analysis demonstrated IκBα, a tumor-suppressor as well as an NF-κB inhibitor, was a direct target of miR-668. Further, miR-668 overexpression inhibited IκBα expression, activated NF-κB, thus, increased radioresistance of MCF-7 and T-47D cells. Conversely, miR-668 knockdown restored IκBα expression, suppressed NF-κB, increased radiosensitivity of MCF-7R and T-47DR cells.

CONCLUSION

Our findings suggest miR-668 is involved in the radioresistance of breast cancer cells and miR-668-IκBα-NF-κB axis may be a novel candidate for developing rational therapeutic strategies for human breast cancer treatment.

MLN8054, a small molecule inhibitor of aurora kinase a, sensitizes androgen-resistant prostate cancer to radiation

PURPOSE

To determine whether MLN8054, an Aurora kinase A (Aurora-A) inhibitor causes radiosensitization in androgen-insensitive prostate cancer cells in vitro and in vivo.

METHODS AND MATERIALS

In vitro studies consisted of culturing PC3 and DU145 prostate cancer cells and then immunoblotting Aurora A and phospho-Aurora A after radiation and/or nocodazole with MLN8054. Phases of the cell cycle were measured with flow cytometry. PC3 and DU145 cell lines were measured for survival after treatment with MLN8054 and radiation. Immunofluorescence measured γ-H2AX in the PC3 and DU145 cells after treatment. In vivo studies looked at growth delay of PC3 tumor cells in athymic nude mice. PC3 cells grew for 6 to 8 days in mice treated with radiation, MLN8054, or combined for 7 more days. Tumors were resected and fixed on paraffin and stained for von Willebrand factor, Ki67, and caspase-3.

RESULTS

In vitro inhibition of Aurora-A by MLN8054 sensitized prostate cancer cells, as determined by dose enhancement ratios in clonogenic assays. These effects were associated with sustained DNA double-strand breaks, as evidenced by increased immunofluorescence for γ-H2AX and significant G2/M accumulation and polyploidy. In vivo, the addition of MLN8054 (30 mg/kg/day) to radiation in mouse prostate cancer xenografts (PC3 cells) significantly increased tumor growth delay and apoptosis (caspase-3 staining), with reduction in cell proliferation (Ki67 staining) and vascular density (von Willebrand factor staining).

CONCLUSION

MLN8054, a novel small molecule Aurora-A inhibitor showed radiation sensitization in androgen-insensitive prostate cancer in vitro and in vivo. This warrants the clinical development of MLN8054 with radiation for prostate cancer patients.

Novel histone deacetylase inhibitor CG200745 induces clonogenic cell death by modulating acetylation of p53 in cancer cells

Histone deacetylase (HDAC) plays an important role in cancer onset and progression. Therefore, inhibition of HDAC offers potential as an effective cancer treatment regimen. CG200745, (E)-N(1)-(3-(dimethylamino)propyl)-N(8)-hydroxy-2-((naphthalene-1-loxy)methyl)oct-2-enediamide, is a novel HDAC inhibitor presently undergoing a phase I clinical trial. Enhancement of p53 acetylation by HDAC inhibitors induces cell cycle arrest, differentiation, and apoptosis in cancer cells. The purpose of the present study was to investigate the role of p53 acetylation in the cancer cell death caused by CG200745. CG200745-induced clonogenic cell death was 2-fold greater in RKO cells expressing wild-type p53 than in p53-deficient RC10.1 cells. CG200745 treatment was also cytotoxic to PC-3 human prostate cancer cells, which express wild-type p53. CG200745 increased acetylation of p53 lysine residues K320, K373, and K382. CG200745 induced the accumulation of p53, promoted p53-dependent transactivation, and enhanced the expression of MDM2 and p21(Waf1/Cip1) proteins, which are encoded by p53 target genes. An examination of CG200745 effects on p53 acetylation using cells transfected with various p53 mutants showed that cells expressing p53 K382R mutants were significantly resistant to CG200745-induced clonogenic cell death compared with wild-type p53 cells. Moreover, p53 transactivation in response to CG200745 was suppressed in all cells carrying mutant forms of p53, especially K382R. Taken together, these results suggest that acetylation of p53 at K382 plays an important role in CG200745-induced p53 transactivation and clonogenic cell death.