Gary Wildey

Low PIAS3 Expression in Malignant Mesothelioma Is Associated with Increased STAT3 Activation and Poor Patient Survival

Purpose: Deregulation of STAT3 activation is a hallmark of many cancer cells, and the underlying mechanisms are subject to intense investigation. We examined the extent of PIAS3 expression in mesothelioma cells and human tumor samples and determined the functional effects of PIAS3 expression on STAT3 signaling. Experimental design: We evaluated the expression of PIAS3 in mesothelioma tumors from patients and correlated the expression levels with the course of the disease. We also measured the effects of enhanced PIAS3 activity on STAT3 signaling, cellular growth, and viability in cultured mesothelioma cells. Results: Gene expression databases revealed that mesotheliomas have the lowest levels of PIAS3 transcripts among solid tumors. PIAS3 expression in human mesothelioma tumors is significantly correlated with overall survival intervals (P = 0.058). The high expression of PIAS3 is predictive of a favorable prognosis and decreases the probability of death within one year after diagnosis by 44%. PIAS3 expression is functionally linked to STAT3 activation in mesothelioma cell lines. STAT3 downregulation with siRNA or enhanced expression of PIAS3 both inhibited mesothelioma cell growth and induced apoptosis. Mesothelioma cells are sensitive to curcumin and respond by the induction of PIAS3. Corroborative evidence has been obtained from STAT3 inhibition experiments. Exposure of the cells to a peptide derived from the PIAS3 protein that interferes with STAT3 function resulted in apoptosis induction and the inhibition of cell growth. Conclusion: These results suggest that PIAS3 protein expression impacts survival in patients with mesothelioma and that PIAS3 activation could become a therapeutic strategy. Clin Cancer Res; 20(19); 5124–32. ©2014 AACR.

RET Mutation and Expression in Small-Cell Lung Cancer

Background: There is growing interest in defining the somatic mutations associated with small-cell lung cancer (SCLC). Unfortunately, a serious blockade to genomic analyses of this disease is a limited access to tumors because surgery is rarely performed. We used our clinical/pathologic database of SCLC patients to determine the availability of biopsy specimens that could be used for genomic studies and to identify tumors for initial oncogene analysis. Methods: DNA was extracted from six tumors, three primary and three metastatic, and analyzed by SEQUENOM platform technology. Results: Primary-resected tumor tissue represents less than 3% of all diagnostic specimens in this disease, highlighting the limited access to tissue sufficient for comprehensive genomic analyses. We identified an activating M918T RET somatic mutation in a metastatic SCLC tumor specimen. Bioinformatic search identified RET mutations in other SCLC studies. Stable overexpression of both mutant M918T and wild-type RET in two SCLC cell lines, H1048 and SW1271, activated ERK signaling, MYC expression, and increased cell proliferation, particularly by mutant RET. Stable cells became sensitized to the RET tyrosine kinase inhibitors, vandetanib and ponatinib. Further analysis of RET mRNA expression in SCLC revealed wide variability in both cells and tumors, and SCLC cells demonstrated significantly higher RET expression compared with adenocarcinoma lung cells. Conclusions: Our data suggest that a subpopulation of SCLC patients may derive benefit from tyrosine kinase inhibitors targeting RET. Coupled with the presence of RET fusion proteins in non-small-cell lung cancer, our data indicate an emerging role for RET in SCLC.

Small Cell Lung Cancer Exhibits Frequent Inactivating Mutations in the Histone Methyltransferase KMT2D/MLL2: CALGB 151111 (Alliance)

Introduction SCLC is a lethal neuroendocrine tumor type that is highly prone to metastasis. There is an urgency to understand the mutated genes that promote SCLC, as there are no approved targeted therapies yet available. SCLC is rarely resected, limiting the number of samples available for genomic analyses of somatic mutations. Methods To identify potential driver mutations in human SCLC we sequenced the whole exomes of 18 primary SCLCs and seven cell lines along with matched normal controls. We extended these data by resequencing a panel of genes across 40 primary SCLCs and 48 cell lines. Results We report frequent mutations in the lysine methyltransferase 2D gene (KMT2D) (also known as MLL2), a key regulator of transcriptional enhancer function. KMT2D exhibited truncating nonsense/frameshift/splice site mutations in 8% of SCLC tumors and 17% of SCLC cell lines. We found that KMT2D mutation in human SCLC cell lines was associated with reduced lysine methyltransferase 2D protein levels and reduced monomethylation of histone H3 lysine 4, a mark associated with transcriptional enhancers. We also found mutations in other genes associated with transcriptional enhancer control, including CREB binding protein gene (CREBBP), E1A binding protein p300 gene (EP300), and chromodomain helicase DNA binding protein 7 gene (CHD7), and we report mutations in additional chromatin remodeling genes such as polybromo 1 gene (PBRM1). Conclusions These data indicate that KMT2D is one of the major mutated genes in SCLC, and they point to perturbation of transcriptional enhancer control as potentially contributing to SCLC.

PIAS3 expression in squamous cell lung cancer is low and predicts overall survival

Unlike lung adenocarcinoma, little progress has been made in the treatment of squamous cell lung carcinoma (SCC). The Cancer Genome Atlas (TCGA) has recently reported that receptor tyrosine kinase signaling pathways are altered in 26% of SCC tumors, validating the importance of downstream Signal Transducers and Activators of Transcription 3 (STAT3) activity as a prime therapeutic target in this cancer. In the present report we examine the status of an endogenous inhibitor of STAT3, called Protein Inhibitor of Activated STAT3 (PIAS3), in SCC and its potential role in this disease. We examine PIAS3 expression in SCC tumors and cell lines by immunohistochemistry of a tissue microarray and western blotting. PIAS3 mRNA expression and survival data are analyzed in the TCGA data set. SCC cell lines are treated with curcumin to regulate PIAS3 expression and cell growth. PIAS3 protein expression is decreased in a majority of lung SCC tumors and cell lines. Analysis of PIAS3 mRNA transcript levels demonstrated that low PIAS3 levels predicted poor survival; Cox regression analysis revealed a hazard ratio of 0.57 (95% CI: 0.37–0.87), indicating a decrease in the risk of death by 43% for every unit elevation in PIAS3 gene expression. Curcumin treatment increased endogenous PIAS3 expression and decreased cell growth and viability in Calu‐1 cells, a model of SCC. Our results implicate PIAS3 loss in the pathology of lung SCC and raise the therapeutic possibility of upregulating PIAS3 expression as a single target that can suppress signaling from the multiple receptor tyrosine kinase receptors found to be amplified in SCC.

Pharmacogenomic Approach to Identify Drug Sensitivity in Small-Cell Lung Cancer

There are currently no molecular targeted approaches to treat small-cell lung cancer (SCLC) similar to those used successfully against non-small-cell lung cancer. This failure is attributable to our inability to identify clinically-relevant subtypes of this disease. Thus, a more systematic approach to drug discovery for SCLC is needed. In this regard, two comprehensive studies recently published in Nature, the Cancer Cell Line Encyclopedia and the Cancer Genome Project, provide a wealth of data regarding the drug sensitivity and genomic profiles of many different types of cancer cells. In the present study we have mined these two studies for new therapeutic agents for SCLC and identified heat shock proteins, cyclin-dependent kinases and polo-like kinases (PLK) as attractive molecular targets with little current clinical trial activity in SCLC. Remarkably, our analyses demonstrated that most SCLC cell lines clustered into a single, predominant subgroup by either gene expression or CNV analyses, leading us to take a pharmacogenomic approach to identify subgroups of drug-sensitive SCLC cells. Using PLK inhibitors as an example, we identified and validated a gene signature for drug sensitivity in SCLC cell lines. This gene signature could distinguish subpopulations among human SCLC tumors, suggesting its potential clinical utility. Finally, circos plots were constructed to yield a comprehensive view of how transcriptional, copy number and mutational elements affect PLK sensitivity in SCLC cell lines. Taken together, this study outlines an approach to predict drug sensitivity in SCLC to novel targeted therapeutics.

PIAS3 activates the intrinsic apoptotic pathway in non-small cell lung cancer cells independent of p53 status

Protein inhibitor of activated signal transducer and activator of transcription 3 (STAT3) (PIAS3) is an endogenous inhibitor of STAT3 that negatively regulates STAT3 transcriptional activity and cell growth and demonstrates limited expression in the majority of human squamous cell carcinomas of the lung. In this study, we sought to determine whether PIAS3 inhibits cell growth in non‐small cell lung cancer cell lines by inducing apoptosis. Our results demonstrate that overexpression of PIAS3 promotes mitochondrial depolarization, leading to cytochrome c release, caspase 9 and 3 activation and poly (ADP‐ribose) polymerase cleavage. This intrinsic pathway activation was associated with decreased Bcl‐xL expression and increased Noxa expression and was independent of p53 status. Furthermore, PIAS3 inhibition of STAT3 activity was also p53 independent. Microarray experiments were performed to discover STAT3‐independent mediators of PIAS3‐induced apoptosis by comparing the apoptotic gene expression signature induced by PIAS3 overexpression with that induced by STAT3 siRNA. The results showed that a subset of apoptotic genes was uniquely expressed only after PIAS3 expression. Thus, PIAS3 may represent a promising lung cancer therapeutic target because of its p53‐independent efficacy and its potential to synergize with Bcl‐2 targeted inhibitors.

CD30 Is a Potential Therapeutic Target in Malignant Mesothelioma

CD30 is a cytokine receptor belonging to the TNF superfamily (TNFRSF8) that acts as a regulator of apoptosis. The presence of CD30 antigen is important in the diagnosis of Hodgkin disease and anaplastic large cell lymphoma. There have been sporadic reports of CD30 expression in nonlymphoid tumors, including malignant mesothelioma. Given the remarkable success of brentuximab vedotin, an antibody–drug conjugate directed against CD30 antigen, in lymphoid malignancies, we undertook a study to examine the incidence of CD30 in mesothelioma and to investigate the ability to target CD30 antigen in mesothelioma. Mesothelioma tumor specimens (N = 83) were examined for CD30 expression by IHC. Positive CD30 expression was noted in 13 mesothelioma specimens, primarily those of epithelial histology. There was no significant correlation of CD30 positivity with tumor grade, stage, or survival. Examination of four mesothelioma cell lines (H28, H2052, H2452, and 211H) for CD30 expression by both FACS analysis and confocal microscopy showed that CD30 antigen localized to the cell membrane. Brentuximab vedotin treatment of cultured mesothelioma cells produced a dose-dependent decrease in cell growth and viability at clinically relevant concentrations. Our studies validate the presence of CD30 antigen in a subgroup of epithelial-type mesothelioma tumors and indicate that selected mesothelioma patients may derive benefit from brentuximab vedotin treatment. Mol Cancer Ther; 14(3); 740–6. ©2015 AACR.

RICTOR amplification identifies a subgroup in small cell lung cancer and predicts response to drugs targeting mTOR

Small cell lung cancer (SCLC) is an aggressive cancer that represents ~15% of all lung cancers. Currently there are no targeted therapies to treat SCLC. Our genomic analysis of a metastatic SCLC cohort identified recurrent RICTOR amplification. Here, we examine the translational potential of this observation. RICTOR was the most frequently amplified gene observed (~14% patients), and co-amplified with FGF10 and IL7R on chromosome 5p13. RICTOR copy number variation correlated with RICTOR protein expression in SCLC cells. In parallel, cells with RICTOR copy number (CN) gain showed increased sensitivity to three mTOR inhibitors, AZD8055, AZD2014 and INK128 in cell growth assays, with AZD2014 demonstrating the best inhibition of downstream signaling. SCLC cells with RICTOR CN gain also migrated more rapidly in chemotaxis and scratch wound assays and were again more sensitive to mTOR inhibitors. The overall survival in SCLC patients with RICTOR amplification was significantly decreased (p = 0.021). Taken together, our results suggest that SCLC patients with RICTOR amplification may constitute a clinically important subgroup because of their potential response to mTORC1/2 inhibitors.

Reciprocal expression of INSM1 and YAP1 defines subgroups in small cell lung cancer

The majority of small cell lung cancer (SCLC) patients demonstrate initial chemo-sensitivity, whereas a distinct subgroup of SCLC patients, termed chemo-refractory, do not respond to treatment. There is little understanding of how to distinguish these patients prior to disease treatment. Here we used gene expression profiling to stratify SCLC into subgroups and characterized a molecular phenotype that may identify, in part, chemo-refractive SCLC patients. Two subgroups of SCLC were identified in both cell lines and tumors by the reciprocal expression of two genes; INSM1, a neuroendocrine transcription factor, and YAP1, a key mediator of the Hippo pathway. The great majority of tumors expressed INSM1, which was prognostic for increased progression-free survival and associated with chemo-sensitivity in cell lines. YAP1 is expressed in a minority of SCLC tumors and was shown in cell lines to be downstream of the retinoblastoma protein (RB1) and associated with decreased drug sensitivity. RB1 expression in SCLC cell lines sensitizes them to CDK4/6 inhibitors. Wild-type RB1 mutation status, used as a surrogate marker of YAP1 expression, was prognostic for decreased patient survival and increased chemo-refractory tumor response. Thus, the reciprocal expression of INSM1 and YAP1 appears to stratify SCLC into distinct subgroups and may be useful, along with RB1 mutation status, to identify chemo-refractory SCLC patients.

The FACT inhibitor CBL0137 synergizes with cisplatin in small cell lung cancer by increasing NOTCH1 expression and targeting tumor-initiating cells

Traditional treatments of small-cell lung cancer (SCLC) with cisplatin, a standard-of-care therapy, spare the tumor-initiating cells (TIC) that mediate drug resistance. Here we report a novel therapeutic strategy that preferentially targets TICs in SCLC, in which cisplatin is combined with CBL0137, an inhibitor of the histone chaperone facilitates chromatin transcription (FACT), which is highly expressed in TICs. Combination of cisplatin and CBL0137 killed patient-derived and murine SCLC cell lines synergistically. In response to CBL0137 alone, TICs were more sensitive than non-TICs, in part, because CBL0137 increased expression of the tumor suppressor NOTCH1 by abrogating the binding of negative regulator SP3 to the NOTCH1 promoter, and in part because treatment decreased the high expression of stem cell transcription factors. The combination of cisplatin and CBL0137 greatly reduced the growth of a patient-derived xenograft in mice and also the growth of a syngeneic mouse SCLC tumor. Thus, CBL0137 can be a highly effective drug against SCLC, especially in combination with cisplatin.Significance: These findings reveal a novel therapeutic regimen for SCLC, combining cisplatin with an inhibitor that preferentially targets tumor-initiating cells. Cancer Res; 78(9); 2396-406. ©2018 AACR.