Anna S. Nikonova

Aurora A kinase (AURKA) in normal and pathological cell division.

Temporally and spatially controlled activation of the Aurora A kinase (AURKA) regulates centrosome maturation, entry into mitosis, formation and function of the bipolar spindle, and cytokinesis. Genetic amplification and mRNA and protein overexpression of Aurora A are common in many types of solid tumor, and associated with aneuploidy, supernumerary centrosomes, defective mitotic spindles, and resistance to apoptosis. These properties have led Aurora A to be considered a high-value target for development of cancer therapeutics, with multiple agents currently in early-phase clinical trials. More recently, identification of additional, non-mitotic functions and means of activation of Aurora A during interphase neurite elongation and ciliary resorption have significantly expanded our understanding of its function, and may offer insights into the clinical performance of Aurora A inhibitors. Here we review the mitotic and non-mitotic functions of Aurora A, discuss Aurora A regulation in the context of protein structural information, and evaluate progress in understanding and inhibiting Aurora A in cancer.

Calmodulin activation of Aurora-A kinase (AURKA) is required during ciliary disassembly and in mitosis.

This study demonstrates for the first time that binding of calcium-activated calmodulin to a minimal interaction site within the disordered N-terminal domain is required for the essential Aurora-A activity in mitosis and in regulation of ciliary disassembly.

Inhibiting the HSP90 chaperone slows cyst growth in a mouse model of autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is a progressive genetic syndrome with an incidence of 1:500 in the population, arising from inherited mutations in the genes for polycystic kidney disease 1 (PKD1) or polycystic kidney disease 2 (PKD2). Typical onset is in middle age, with gradual replacement of renal tissue with thousands of fluid-filled cysts, resulting in end-stage renal disease requiring dialysis or kidney transplantation. There currently are no approved therapies to slow or cure ADPKD. Mutations in the PKD1 and PKD2 genes abnormally activate multiple signaling proteins and pathways regulating cell proliferation, many of which we observe, through network construction, to be regulated by heat shock protein 90 (HSP90). Inhibiting HSP90 with a small molecule, STA-2842, induces the degradation of many ADPKD-relevant HSP90 client proteins in Pkd1−/− primary kidney cells and in vivo. Using a conditional Cre-mediated mouse model to inactivate Pkd1 in vivo, we find that weekly administration of STA-2842 over 10 wk significantly reduces initial formation of renal cysts and kidney growth and slows the progression of these phenotypes in mice with preexisting cysts. These improved disease phenotypes are accompanied by improved indicators of kidney function and reduced expression and activity of HSP90 clients and their effectors, with the degree of inhibition correlating with cystic expansion in individual animals. Pharmacokinetic analysis indicates that HSP90 is overexpressed and HSP90 inhibitors are selectively retained in cystic versus normal kidney tissue, analogous to the situation observed in solid tumors. These results provide an initial justification for evaluating HSP90 inhibitors as therapeutic agents for ADPKD.

The hallmarks of cancer: relevance to the pathogenesis of polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is a progressive inherited disorder in which renal tissue is gradually replaced with fluid-filled cysts, giving rise to chronic kidney disease (CKD) and progressive loss of renal function. ADPKD is also associated with liver ductal cysts, hypertension, chronic pain and extra-renal problems such as cerebral aneurysms. Intriguingly, improved understanding of the signalling and pathological derangements characteristic of ADPKD has revealed marked similarities to those of solid tumours, even though the gross presentation of tumours and the greater morbidity and mortality associated with tumour invasion and metastasis would initially suggest entirely different disease processes. The commonalities between ADPKD and cancer are provocative, particularly in the context of recent preclinical and clinical studies of ADPKD that have shown promise with drugs that were originally developed for cancer. The potential therapeutic benefit of such repurposing has led us to review in detail the pathological features of ADPKD through the lens of the defined, classic hallmarks of cancer. In addition, we have evaluated features typical of ADPKD, and determined whether evidence supports the presence of such features in cancer cells. This analysis, which places pathological processes in the context of defined signalling pathways and approved signalling inhibitors, highlights potential avenues for further research and therapeutic exploitation in both diseases.

CAS proteins in health and disease: An update

The CAS family of scaffolding proteins has increasingly attracted scrutiny as important for regulation of cancer‐associated signaling. BCAR1 (also known as p130Cas), NEDD9 (HEF1, Cas‐L), EFS (Sin), and CASS4 (HEPL) are regulated by and mediate cell attachment, growth factor, and chemokine signaling. Altered expression and activity of CAS proteins are now known to promote metastasis and drug resistance in cancer, influence normal development, and contribute to the pathogenesis of heart and pulmonary disease. In this article, we provide an update on recently published studies describing signals regulating and regulated by CAS proteins, and evidence for biological activity of CAS proteins in normal development, cancer, and other pathological conditions.

Targeting C4-Demethylating Genes in the Cholesterol Pathway Sensitizes Cancer Cells to EGF Receptor Inhibitors via Increased EGF Receptor Degradation

UNLABELLED Persistent signaling by the oncogenic EGF receptor (EGFR) is a major source of cancer resistance to EGFR targeting. We established that inactivation of 2 sterol biosynthesis pathway genes, SC4MOL (sterol C4-methyl oxidase-like) and its partner, NSDHL (NADP-dependent steroid dehydrogenase-like), sensitized tumor cells to EGFR inhibitors. Bioinformatics modeling of interactions for the sterol pathway genes in eukaryotes allowed us to hypothesize and then extensively validate an unexpected role for SC4MOL and NSDHL in controlling the signaling, vesicular trafficking, and degradation of EGFR and its dimerization partners, ERBB2 and ERBB3. Metabolic block upstream of SC4MOL with ketoconazole or CYP51A1 siRNA rescued cancer cell viability and EGFR degradation. Inactivation of SC4MOL markedly sensitized A431 xenografts to cetuximab, a therapeutic anti-EGFR antibody. Analysis of Nsdhl-deficient Bpa(1H/+) mice confirmed dramatic and selective loss of internalized platelet-derived growth factor receptor in fibroblasts, and reduced activation of EGFR and its effectors in regions of skin lacking NSDHL. SIGNIFICANCE This work identifies a critical role for SC4MOL and NSDHL in the regulation of EGFR signaling and endocytic trafficking and suggests novel strategies to increase the potency of EGFR antagonists in tumors.

Musashi-2 (MSI2) supports TGF-β signaling and inhibits claudins to promote non-small cell lung cancer (NSCLC) metastasis

Significance The evolutionarily conserved RNA-binding protein Musashi-2 (MSI2) regulates mRNA translation and influences multiple biological processes, including maintenance of stem cell identity. This work for the first time, to our knowledge, identifies that more aggressive patient tumors have higher MSI2 levels. We define a critical role for MSI2 in supporting non-small cell lung cancer (NSCLC) invasiveness and further define claudins 3, 5, and 7 (CLDN3, CLDN5, and CLDN7), TGF-β receptor 1 (TGFβR1), and the small mothers against decapentaplegic homolog 3 (SMAD3) as targets through which MSI2 regulates this process. The observation that MSI2 expression is progressively elevated from an early stage in human NSCLC tumors suggests that this protein may play an essential role in the reprogramming of TGF-β signaling from growth-inhibiting to invasion-promoting during oncogenesis. Non-small cell lung cancer (NSCLC) has a 5-y survival rate of ∼16%, with most deaths associated with uncontrolled metastasis. We screened for stem cell identity-related genes preferentially expressed in a panel of cell lines with high versus low metastatic potential, derived from NSCLC tumors of KrasLA1/+;P53R172HΔG/+ (KP) mice. The Musashi-2 (MSI2) protein, a regulator of mRNA translation, was consistently elevated in metastasis-competent cell lines. MSI2 was overexpressed in 123 human NSCLC tumor specimens versus normal lung, whereas higher expression was associated with disease progression in an independent set of matched normal/primary tumor/lymph node specimens. Depletion of MSI2 in multiple independent metastatic murine and human NSCLC cell lines reduced invasion and metastatic potential, independent of an effect on proliferation. MSI2 depletion significantly induced expression of proteins associated with epithelial identity, including tight junction proteins [claudin 3 (CLDN3), claudin 5 (CLDN5), and claudin 7 (CLDN7)] and down-regulated direct translational targets associated with epithelial–mesenchymal transition, including the TGF-β receptor 1 (TGFβR1), the small mothers against decapentaplegic homolog 3 (SMAD3), and the zinc finger proteins SNAI1 (SNAIL) and SNAI2 (SLUG). Overexpression of TGFβRI reversed the loss of invasion associated with MSI2 depletion, whereas overexpression of CLDN7 inhibited MSI2-dependent invasion. Unexpectedly, MSI2 depletion reduced E-cadherin expression, reflecting a mixed epithelial–mesenchymal phenotype. Based on this work, we propose that MSI2 provides essential support for TGFβR1/SMAD3 signaling and contributes to invasive adenocarcinoma of the lung and may serve as a predictive biomarker of NSCLC aggressiveness.

Quantification of excision repair cross-complementing group 1 and survival in p16-negative squamous cell head and neck cancers.

Purpose: Multimodality treatment of squamous cell carcinoma of the head and neck (SCCHN) often involves radiotherapy and cisplatin-based therapy. Elevated activity of DNA repair mechanisms, such as the nucleotide excision repair (NER) pathway, of which ERCC1 is a rate-limiting element, are associated with cisplatin and possibly RT resistance. We have determined excision repair cross-complementing group 1 (ERCC1) expression in human papillomavirus (HPV)-negative SCCHN treated with surgery [±adjuvant radiotherapy/chemoradiation (CRT)]. Experimental Design: We assessed ERCC1 protein expression in archival tumors using immunofluorescence staining and automatic quantitative analysis (AQUA) with three antibodies to ERCC1 (8F1, FL297, and HPA029773). Analysis with Classification and Regression Tree (CART) methods ascertained the cutoff points between high/low ERCC1 expression. Multivariable analysis adjusted for age, T, and N stage. Kaplan–Meier curves determined median survival. ERCC1 expression at initial tumor presentation and in recurrent disease were compared. Performance characteristics of antibodies were assessed. Results: ERCC1 low/high groups were defined on the basis of AQUA analysis with 8F1/2009, FL297, and HPA029773. Among patients treated with surgery plus adjuvant radiotherapy/CRT, longer median survival was observed in ERCC1-low versus ERCC1-high tumors (64 vs. 29 months; P = 0.02; HPA029773). Data obtained with HPA029773 indicated no survival difference among patients treated only with surgery. Recurrent cancers had lower ERCC1 AQUA scores than tumors from initial presentation. Extensive characterization indicated optimal specificity and performance by the HPA029773 antibody. Conclusions: Using AQUA, with the specific ERCC1 antibody HPA029773, we found a statistical difference in survival among high/low-ERCC1 tumors from patients treated with surgery and adjuvant radiotherapy. Clin Cancer Res; 19(23); 6633–43. ©2013 AACR.

Nedd9 restrains renal cystogenesis in Pkd1−/− mice

Significance This study uses mouse models for the first time to our knowledge to identify that NEDD9, a nonenzymatic scaffolding protein that is commonly amplified in cancer, has an important restraining function for the development of renal cysts in autosomal dominant polycystic kidney disease (ADPKD). In the absence of NEDD9, failure to activate Aurora-A kinase causes multiple abnormalities in cilia, intensifying the effect of genetic deficiency of mutations in the polycystic kidney disease (PKD) 1 gene, the most common cause of PKD. As important implications, clinical inhibitors of Aurora-A also intensified ADPKD induced by mutation of PKD1, suggesting caution in use of these agents, whereas recently reported polymorphisms in Nedd9 may contribute to the genetic heterogeneity of ADPKD presentation in affected families. Mutations inactivating the cilia-localized Pkd1 protein result in autosomal dominant polycystic kidney disease (ADPKD), a serious inherited syndrome affecting ∼1 in 500 people, in which accumulation of renal cysts eventually destroys kidney function. Severity of ADPKD varies throughout the population, for reasons thought to involve differences both in intragenic Pkd1 mutations and in modifier alleles. The scaffolding protein NEDD9, commonly dysregulated during cancer progression, interacts with Aurora-A (AURKA) kinase to control ciliary resorption, and with Src and other partners to influence proliferative signaling pathways often activated in ADPKD. We here demonstrate Nedd9 expression is deregulated in human ADPKD and a mouse ADPKD model. Although genetic ablation of Nedd9 does not independently influence cystogenesis, constitutive absence of Nedd9 strongly promotes cyst formation in the tamoxifen-inducible Pkd1fl/fl;Cre/Esr1+ mouse model of ADPKD. This cystogenic effect is associated with striking morphological defects in the cilia of Pkd1−/−;Nedd9−/− mice, associated with specific loss of ciliary localization of adenylase cyclase III in the doubly mutant genotype. Ciliary phenotypes imply a failure of Aurora-A activation: Compatible with this idea, Pkd1−/−;Nedd9−/− mice had ciliary resorption defects, and treatment of Pkd1−/− mice with a clinical Aurora-A kinase inhibitor exacerbated cystogenesis. In addition, activation of the ADPKD-associated signaling effectors Src, Erk, and the mTOR effector S6 was enhanced, and Ca2+ response to external stimuli was reduced, in Pkd1−/−;Nedd9−/− versus Pkd1−/− mice. Together, these results indicated an important modifier action of Nedd9 on ADPKD pathogenesis involving failure to activate Aurora-A.

A Novel HSP90 Inhibitor–Drug Conjugate to SN38 Is Highly Effective in Small Cell Lung Cancer

Purpose: Small cell lung cancer (SCLC) is a highly aggressive disease representing 12% to 13% of total lung cancers, with median survival of <2 years. No targeted therapies have proven effective in SCLC. Although most patients respond initially to cytotoxic chemotherapies, resistance rapidly emerges, response to second-line agents is limited, and dose-limiting toxicities (DLT) are a major issue. This study performs preclinical evaluation of a new compound, STA-8666, in SCLC. Experimental Design: To avoid DLT for useful cytotoxic agents, the recently developed drug STA-8666 combines a chemical moiety targeting active HSP90 (concentrated in tumors) fused via cleavable linker to SN38, the active metabolite of irinotecan. We compare potency and mechanism of action of STA-8666 and irinotecan in vitro and in vivo. Results: In two SCLC xenograft and patient-derived xenograft models, STA-8666 was tolerated without side effects up to 150 mg/kg. At this dose, STA-8666 controlled or eliminated established tumors whether used in a first-line setting or in tumors that had progressed following treatment on standard first- and second-line agents for SCLC. At 50 mg/kg, STA-8666 strongly enhanced the action of carboplatin. Pharmacokinetic profiling confirmed durable STA-8666 exposure in tumors compared with irinotecan. STA-8666 induced a more rapid, robust, and stable induction of cell-cycle arrest, expression of signaling proteins associated with DNA damage and cell-cycle checkpoints, and apoptosis in vitro and in vivo, in comparison with irinotecan. Conclusions: Together, these results strongly support clinical development of STA-8666 for use in the first- or second-line setting for SCLC. Clin Cancer Res; 22(20); 5120–9. ©2016 AACR.