Chandra Goparaju

Programmed necrosis induced by asbestos in human mesothelial cells causes high-mobility group box 1 protein release and resultant inflammation.

Asbestos carcinogenesis has been linked to the release of cytokines and mutagenic reactive oxygen species (ROS) from inflammatory cells. Asbestos is cytotoxic to human mesothelial cells (HM), which appears counterintuitive for a carcinogen. We show that asbestos-induced HM cell death is a regulated form of necrosis that links to carcinogenesis. Asbestos-exposed HM activate poly(ADP-ribose) polymerase, secrete H2O2, deplete ATP, and translocate high-mobility group box 1 protein (HMGB1) from the nucleus to the cytoplasm, and into the extracellular space. The release of HMGB1 induces macrophages to secrete TNF-α, which protects HM from asbestos-induced cell death and triggers a chronic inflammatory response; both favor HM transformation. In both mice and hamsters injected with asbestos, HMGB1 was specifically detected in the nuclei, cytoplasm, and extracellular space of mesothelial and inflammatory cells around asbestos deposits. TNF-α was coexpressed in the same areas. HMGB1 levels in asbestos-exposed individuals were significantly higher than in nonexposed controls (P < 0.0001). Our findings identify the release of HMGB1 as a critical initial step in the pathogenesis of asbestos-related disease, and provide mechanistic links between asbestos-induced cell death, chronic inflammation, and carcinogenesis. Chemopreventive approaches aimed at inhibiting the chronic inflammatory response, and especially blocking HMGB1, may decrease the risk of malignant mesothelioma among asbestos-exposed cohorts.

hsa-miR-29c* Is Linked to the Prognosis of Malignant Pleural Mesothelioma

The inability to forecast outcomes for malignant mesothelioma prevents clinicians from providing aggressive multimodality therapy to the most appropriate individuals who may benefit from such an approach. We investigated whether specific microRNAs (miR) could segregate a largely surgically treated group of mesotheliomas into good or bad prognosis categories. A training set of 44 and a test set of 98 mesothelioma tumors were analyzed by a custom miR platform, along with 9 mesothelioma cell lines and 3 normal mesothelial lines. Functional implications as well as downstream targets of potential prognostic miRs were investigated. In both the training and test sets, hsa-miR-29c* was an independent prognostic factor for time to progression as well as survival after surgical cytoreduction. The miR was expressed at higher levels in epithelial mesothelioma, and the level of this miR could segregate patients with this histology into groups with differing prognosis. Increased expression of hsa-miR-29c* predicted a more favorable prognosis, and overexpression of the miR in mesothelioma cell lines resulted in significantly decreased proliferation, migration, invasion, and colony formation. Moreover, major epigenetic regulation of mesothelioma is mediated by hsa-miR-29c* and was shown through downregulation of DNA methyltransferases as well as upregulation of demethylating genes. A single miR has the potential to be a prognostic biomarker in mesothelioma, and validation of these findings as well as investigation of its downstream targets may give insight for potential therapies in the future.

Whole exome sequencing reveals frequent genetic alterations in BAP1, NF2, CDKN2A and CUL1 in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is an aggressive neoplasm associated with asbestos exposure. Although previous studies based on candidate gene approaches have identified important common somatic mutations in MPM, these studies have focused on small sets of genes and have provided a limited view of the genetic alterations underlying this disease. Here, we performed whole-exome sequencing on DNA from 22 MPMs and matched blood samples, and identified 517 somatic mutations across 490 mutated genes. Integrative analysis of mutations and somatic copy-number alterations revealed frequent genetic alterations in BAP1, NF2, CDKN2A, and CUL1. Our study presents the first unbiased view of the genomic basis of MPM.

Pro-tumorigenic Effects of miR-31 Loss in Mesothelioma

The human genome encodes several hundred microRNA (miRNA) genes that produce small (21–23n) single strand regulatory RNA molecules. Although abnormal expression of miRNAs has been linked to cancer progression, the mechanisms of this dysregulation are poorly understood. Malignant mesothelioma (MM) of pleura is an aggressive and highly lethal cancer resistant to conventional therapies. We and others previously linked loss of the 9p21.3 chromosome in MM with short time to tumor recurrence. In this study, we report that MM cell lines derived from patients with more aggressive disease fail to express miR-31, a microRNA recently linked with suppression of breast cancer metastases. We further demonstrate that this loss is due to homozygous deletion of the miR-31-encoding gene that resides in 9p21.3. Functional assessment of miR-31 activity revealed its ability to inhibit proliferation, migration, invasion, and clonogenicity of MM cells. Re-introduction of miR-31 suppressed the cell cycle and inhibited expression of multiple factors involved in cooperative maintenance of DNA replication and cell cycle progression, including pro-survival phosphatase PPP6C, which was previously associated with chemotherapy and radiation therapy resistance, and maintenance of chromosomal stability. PPP6C, whose mRNA is distinguished with three miR-31-binding sites in its 3′-untranslated region, was consistently down-regulated by miR-31 introduction and up-regulated in clinical MM specimens as compared with matched normal tissues. Taken together, our data suggest that tumor-suppressive propensity of miR-31 can be used for development of new therapies against mesothelioma and other cancers that show loss of the 9p21.3 chromosome.

Early Detection of Malignant Pleural Mesothelioma in Asbestos-Exposed Individuals with a Noninvasive Proteomics-Based Surveillance Tool

Background Malignant pleural mesothelioma (MM) is an aggressive, asbestos-related pulmonary cancer that is increasing in incidence. Because diagnosis is difficult and the disease is relatively rare, most patients present at a clinically advanced stage where possibility of cure is minimal. To improve surveillance and detection of MM in the high-risk population, we completed a series of clinical studies to develop a noninvasive test for early detection. Methodology/Principal Findings We conducted multi-center case-control studies in serum from 117 MM cases and 142 asbestos-exposed control individuals. Biomarker discovery, verification, and validation were performed using SOMAmer proteomic technology, which simultaneously measures over 1000 proteins in unfractionated biologic samples. Using univariate and multivariate approaches we discovered 64 candidate protein biomarkers and derived a 13-marker random forest classifier with an AUC of 0.99±0.01 in training, 0.98±0.04 in independent blinded verification and 0.95±0.04 in blinded validation studies. Sensitivity and specificity at our pre-specified decision threshold were 97%/92% in training and 90%/95% in blinded verification. This classifier accuracy was maintained in a second blinded validation set with a sensitivity/specificity of 90%/89% and combined accuracy of 92%. Sensitivity correlated with pathologic stage; 77% of Stage I, 93% of Stage II, 96% of Stage III and 96% of Stage IV cases were detected. An alternative decision threshold in the validation study yielding 98% specificity would still detect 60% of MM cases. In a paired sample set the classifier AUC of 0.99 and 91%/94% sensitivity/specificity was superior to that of mesothelin with an AUC of 0.82 and 66%/88% sensitivity/specificity. The candidate biomarker panel consists of both inflammatory and proliferative proteins, processes strongly associated with asbestos-induced malignancy. Significance The SOMAmer biomarker panel discovered and validated in these studies provides a solid foundation for surveillance and diagnosis of MM in those at highest risk for this disease.

Reduction of Elevated Plasma Osteopontin Levels With Resection of Non–Small-Cell Lung Cancer

PURPOSE Plasma osteopontin (OPN) levels in advanced non-small-cell lung cancer (NSCLC) correlate with therapeutic response and survival, but the utility of plasma OPN for diagnosis and monitoring of early-stage NSCLC has not been investigated. We hypothesize that plasma OPN levels are elevated in early-stage NSCLC and decrease with resection. PATIENTS AND METHODS Presurgery plasma OPN levels (in ng/mL) were measured by enzyme-linked immunosorbent assay (ELISA) in a discovery set of 60 patients with early-stage NSCLC and were compared with data from 56 cancer-free smokers. Presurgery OPN was validated in an independent cohort of 96 patients with resectable NSCLC. The presurgery levels in the latter cohort were compared with matched postsurgery levels. Perioperative OPN levels were correlated with demographics, tumor characteristics, and perioperative events. OPN was monitored during follow-up. Results Discovery set presurgery NSCLC OPN (271 +/- 31 ng/mL) was higher than smokers (40 +/- 2 ng/mL; P = .001). Presurgery OPN was similar in the NSCLC validation cohort (324 ng/mL +/- 20 ng/mL; P = .134). Postsurgery OPN (256 ng/mL +/- 21 ng/mL) measured at mean of 9.8 weeks (range, 2 to 46 weeks) was lower than presurgery OPN (P = .005). Time from surgery significantly impacted postsurgery OPN: OPN < or = 6 weeks postsurgery (303 n/mL +/- 26 ng/mL) was higher than OPN greater than 6 weeks postsurgery (177 ng/mL +/- 29 ng/mL; P = .003). Multivariate analysis noted correlations between albumin and creatinine to presurgery OPN and use of thoracotomy to postsurgery OPN. Recurrence rate was 5% at 29 weeks mean follow-up. OPN at recurrence was elevated from postsurgery nadir. CONCLUSION Plasma OPN levels are elevated in early-stage NSCLC. They are reduced after resection and appear to increase with recurrence. Plasma OPN may have utility as a biomarker in early-stage NSCLC.

HMGB1 and Its Hyperacetylated Isoform are Sensitive and Specific Serum Biomarkers to Detect Asbestos Exposure and to Identify Mesothelioma Patients

Purpose: To determine whether serum levels of high mobility group box protein 1 (HMGB1) could differentiate malignant mesothelioma patients, asbestos-exposed individuals, and unexposed controls. Experimental Design: Hyperacetylated and nonacetylated HMGB1 (together referred to as total HMGB1) were blindly measured in blood collected from malignant mesothelioma patients (n = 22), individuals with verified chronic asbestos exposure (n = 20), patients with benign pleural effusions (n = 13) or malignant pleural effusions not due to malignant mesothelioma (n = 25), and healthy controls (n = 20). Blood levels of previously proposed malignant mesothelioma biomarkers fibulin-3, mesothelin, and osteopontin were also measured in nonhealthy individuals. Results: HMGB1 serum levels reliably distinguished malignant mesothelioma patients, asbestos-exposed individuals, and unexposed controls. Total HMGB1 was significantly higher in malignant mesothelioma patients and asbestos-exposed individuals compared with healthy controls. Hyperacetylated HMGB1 was significantly higher in malignant mesothelioma patients compared with asbestos-exposed individuals and healthy controls, and did not vary with tumor stage. At the cut-off value of 2.00 ng/mL, the sensitivity and specificity of serum hyperacetylated HMGB1 in differentiating malignant mesothelioma patients from asbestos-exposed individuals and healthy controls was 100%, outperforming other previously proposed biomarkers. Combining HMGB1 and fibulin-3 provided increased sensitivity and specificity in differentiating malignant mesothelioma patients from patients with cytologically benign or malignant non–mesothelioma pleural effusion. Conclusions: Our results are significant and clinically relevant as they provide the first biomarker of asbestos exposure and indicate that hyperacetylated HMGB1 is an accurate biomarker to differentiate malignant mesothelioma patients from individuals occupationally exposed to asbestos and unexposed controls. A trial to independently validate these findings will start soon. Clin Cancer Res; 22(12); 3087–96. ©2016 AACR.

Tumorigenic properties of alternative osteopontin isoforms in mesothelioma.

Osteopontin (SPP1) is an inflammatory cytokine that we previously characterized as a diagnostic marker in patients with asbestos-induced malignant mesothelioma (MM). While SPP1 shows both pro- and anti-tumorigenic biological effects, little is known about the molecular basis of these activities. In this study, we demonstrate that while healthy pleura possesses all three differentially spliced SPP1 isoforms (A-C), in clinical MM specimens isoform A is markedly up-regulated and predominant. To provide a clue to possible functions of the SPP1 isoforms we next performed their functional evaluation via transient expression in MM cell lines. As a result, we report that isoforms A-C demonstrate different activities in cell proliferation, wound closure, and invasion assays. These findings suggest different functions for SPP1 isoforms and underline pro-tumorigenic properties of isoforms A and B.

Keap1 loss promotes Kras -driven lung cancer and results in dependence on glutaminolysis

Treating KRAS-mutant lung adenocarcinoma (LUAD) remains a major challenge in cancer treatment given the difficulties associated with directly inhibiting the KRAS oncoprotein. One approach to addressing this challenge is to define mutations that frequently co-occur with those in KRAS, which themselves may lead to therapeutic vulnerabilities in tumors. Approximately 20% of KRAS-mutant LUAD tumors carry loss-of-function mutations in the KEAP1 gene encoding Kelch-like ECH-associated protein 1 (refs. 2, 3, 4), a negative regulator of nuclear factor erythroid 2-like 2 (NFE2L2; hereafter NRF2), which is the master transcriptional regulator of the endogenous antioxidant response. The high frequency of mutations in KEAP1 suggests an important role for the oxidative stress response in lung tumorigenesis. Using a CRISPR–Cas9-based approach in a mouse model of KRAS-driven LUAD, we examined the effects of Keap1 loss in lung cancer progression. We show that loss of Keap1 hyperactivates NRF2 and promotes KRAS-driven LUAD in mice. Through a combination of CRISPR–Cas9-based genetic screening and metabolomic analyses, we show that Keap1- or Nrf2-mutant cancers are dependent on increased glutaminolysis, and this property can be therapeutically exploited through the pharmacological inhibition of glutaminase. Finally, we provide a rationale for stratification of human patients with lung cancer harboring KRAS/KEAP1- or KRAS/NRF2-mutant lung tumors as likely to respond to glutaminase inhibition.

Lung cancer osteopontin isoforms exhibit angiogenic functional heterogeneity

OBJECTIVE Osteopontin is a multifunctional phosphoprotein with an important but poorly understood role in non-small cell lung cancer pathogenesis. We hypothesize that osteopontin isoforms (OPNa, OPNb, and OPNc) have divergent roles in non-small-cell lung cancer angiogenesis and divergent impact on vascular endothelial growth factor secretion. METHODS We examined mRNA expression using reverse transcriptase-polymerase chain reaction primers for 3 osteopontin isoforms in non-small-cell lung cancer and immortalized bronchial epithelial cell lines, and correlated expression with osteopontin secretion into media detected by enzyme-linked immunosorbent assay. Angiogenic properties conferred by osteopontin isoforms were evaluated by transfecting cDNA plasmids specific to each isoform and controls into non-small-cell lung cancer cell lines, H153 and H358 (low endogenous osteopontin) and A549 and H460 (high endogenous osteopontin), analyzing conditioned media on a bovine capillary endothelial platform, and measuring vascular endothelial growth factor levels by enzyme-linked immunosorbent assay. RESULTS OPNa mRNA expression correlated with osteopontin secretion in cell lines (r = 0.912, P = .0006). OPNa overexpression significantly increased tubule length compared with controls, OPNb had a similar, but less pronounced effect, and OPNc significantly decreased tubule length compared with controls in each cell line. OPNa overexpression was associated with significant increases in vascular endothelial growth factor secretion, whereas OPNb had no effect and OPNc overexpression was associated with significant decreases in vascular endothelial growth factor compared with controls in each cell line. CONCLUSION We demonstrated divergent effects of osteopontin isoforms on non-small-cell lung cancer angiogenesis and vascular endothelial growth factor secretion. OPNa overexpression was associated with increased bovine capillary endothelial tubule length and vascular endothelial growth factor secretion, whereas OPNc was associated with decreases in both. These findings may lead to therapeutic strategies for selective isoform inhibition in non-small cell lung cancer.