Subhankar Chakraborty

The multifaceted roles of neutrophil gelatinase associated lipocalin (NGAL) in inflammation and cancer.

Neutrophil gelatinase associated lipocalin (NGAL), also known as oncogene 24p3, uterocalin, siderocalin or lipocalin 2, is a 24kDa secreted glycoprotein originally purified from a culture of mouse kidney cells infected with simian virus 40 (SV-40). Subsequent investigations have revealed that it is a member of the lipocalin family of proteins that transport small, hydrophobic ligands. Since then, NGAL expression has been reported in several normal tissues where it serves to provide protection against bacterial infection and modulate oxidative stress. Its expression is also dysregulated in several benign and malignant diseases. Its small size, secreted nature and relative stability have led to it being investigated as a diagnostic and prognostic biomarker in numerous diseases including inflammation and cancer. Functional studies, conducted primarily on lipocalin 2 (Lcn2), the mouse homologue of human NGAL have revealed that Lcn2 has a strong affinity for iron complexed to both bacterial siderophores (iron-binding proteins) and certain human proteins like norepinephrine. By sequestering iron-laden siderophores, Lcn2 deprives bacteria of a vital nutrient and thus inhibits their growth (bacteriostatic effect). In malignant cells, its proposed functions range from inhibiting apoptosis (in thyroid cancer cells), invasion and angiogenesis (in pancreatic cancer) to increasing proliferation and metastasis (in breast and colon cancer). Ectopic expression of Lcn2 also promotes BCR-ABL induced chronic myelogenous leukemia in murine models. By transporting iron into and out of the cell, NGAL also regulates iron responsive genes. Further, it stabilizes the proteolytic enzyme matrix metalloprotease-9 (MMP-9) by forming a complex with it, and thereby prevents its autodegradation. The factors regulating NGAL expression are numerous and range from pro-inflammatory cytokines like interleukins, tumor necrosis factor-α and interferons to vitamins like retinoic acid. The purpose of this review article is to examine the expression, structure, regulation and biological role of NGAL and critically assess its potential as a novel diagnostic and prognostic marker in both benign and malignant human diseases.

MUC4 mucin potentiates pancreatic tumor cell proliferation, survival, and invasive properties and interferes with its interaction to extracellular matrix proteins

MUC4, a transmembrane mucin, is aberrantly expressed in pancreatic adenocarcinomas while remaining undetectable in the normal pancreas. Recent studies have shown that the expression of MUC4 is associated with the progression of pancreatic cancer and is inversely correlated with the prognosis of pancreatic cancer patients. In the present study, we have examined the phenotypic and molecular consequences of MUC4 silencing with an aim of establishing the mechanistic basis for its observed role in the pathogenesis of pancreatic cancer. The silencing of MUC4 expression was achieved by stable expression of a MUC4-specific short hairpin RNA in CD18/HPAF, a highly metastatic pancreatic adenocarcinoma cell line. A significant decrease in MUC4 expression was detected in MUC4-knockdown (CD18/HPAF-siMUC4) cells compared with the parental and scrambled short interfering RNA–transfected (CD18/HPAF-Scr) control cells by immunoblot analysis and immunofluorescence confocal microscopy. Consistent with our previous observation, inhibition of MUC4 expression restrained the pancreatic tumor cell growth and metastasis as shown in an orthotopic mouse model. Our in vitro studies revealed that MUC4-associated increase in tumor cell growth resulted from both the enhanced proliferation and reduced cell death. Furthermore, MUC4 expression was also associated with significantly increased invasiveness (P ≤ 0.05) and changes in actin organization. The presence of MUC4 on the cell surface was shown to interfere with the tumor cell-extracellular matrix interactions, in part, by inhibiting the integrin-mediated cell adhesion. An altered expression of growth- and metastasis-associated genes (LI-cadherin, CEACAM6, RAC1, AnnexinA1, thrombomodulin, epiregulin, S100A4, TP53, TP53BP, caspase-2, caspase-3, caspase-7, plakoglobin, and neuregulin-2) was also observed as a consequence of the silencing of MUC4. In conclusion, our study provides experimental evidence that supports the functional significance of MUC4 in pancreatic cancer progression and indicates a novel role for MUC4 in cancer cell signaling. (Mol Cancer Res 2007;5(4):309–20)

Early diagnosis of pancreatic cancer: neutrophil gelatinase-associated lipocalin as a marker of pancreatic intraepithelial neoplasia.

Pancreatic cancer is a highly lethal malignancy with a dismal 5-year survival of less than 5%. The scarcity of early biomarkers has considerably hindered our ability to launch preventive measures for this malignancy in a timely manner. Neutrophil gelatinase-associated lipocalin (NGAL), a 24-kDa glycoprotein, was reported to be upregulated nearly 27-fold in pancreatic cancer cells compared to normal ductal cells in a microarray analysis. Given the need for biomarkers in the early diagnosis of pancreatic cancer, we investigated the expression of NGAL in tissues with the objective of examining if NGAL immunostaining could be used to identify foci of pancreatic intraepithelial neoplasia, premalignant lesions preceding invasive cancer. To examine a possible correlation between NGAL expression and the degree of differentiation, we also analysed NGAL levels in pancreatic cancer cell lines with varying grades of differentiation. Although NGAL expression was strongly upregulated in pancreatic cancer, and moderately in pancreatitis, only a weak expression could be detected in the healthy pancreas. The average composite score for adenocarcinoma (4.26±2.44) was significantly higher than that for the normal pancreas (1.0) or pancreatitis (1.0) (P<0.0001). Further, although both well- and moderately differentiated pancreatic cancer were positive for NGAL, poorly differentiated adenocarcinoma was uniformly negative. Importantly, NGAL expression was detected as early as the PanIN-1 stage, suggesting that it could be a marker of the earliest premalignant changes in the pancreas. Further, we examined NGAL levels in serum samples. Serum NGAL levels were above the cutoff for healthy individuals in 94% of pancreatic cancer and 62.5% each of acute and chronic pancreatitis samples. However, the difference between NGAL levels in pancreatitis and pancreatic cancer was not significant. A ROC curve analysis revealed that ELISA for NGAL is fairly accurate in distinguishing pancreatic cancer from non-cancer cases (area under curve=0.75). In conclusion, NGAL is highly expressed in early dysplastic lesions in the pancreas, suggesting a possible role as an early diagnostic marker for pancreatic cancer. Further, serum NGAL measurement could be investigated as a possible biomarker in pancreatitis and pancreatic adenocarcinoma.

MUC4 mucin-induced epithelial to mesenchymal transition: a novel mechanism for metastasis of human ovarian cancer cells

The acquisition of invasiveness in ovarian cancer (OC) is accompanied by the process of epithelial-to-mesenchymal transition (EMT). The MUC4 mucin is overexpressed in ovarian tumors and has a role in the invasiveness of OC cells. The present study was aimed at evaluating the potential involvement of MUC4 in the metastasis of OC cells by inducing EMT. Ectopic overexpression of MUC4 in OC cells (SKOV3-MUC4) resulted in morphological alterations along with a decreased expression of epithelial markers (E-cadherin and cytokeratin (CK)-18) and an increased expression of mesenchymal markers (N-cadherin and vimentin) compared with the control cells (SKOV3-vector). Also, pro-EMT transcription factors TWIST1, TWIST2 and SNAIL showed an upregulation in SKOV3-MUC4 cells. We further investigated the pathways upstream of N-cadherin, such as focal adhesion kinase (FAK), MKK7, JNK1/2 and c-Jun, which were also activated in the SKOV3-MUC4 cells compared with SKOV3-vector cells. Inhibition of phospho-FAK (pFAK) and pJNK1/2 decreased N-cadherin expression in the MUC4-overexpressing cells, which further led to a significant decrease in cellular motility. Knockdown of N-cadherin decreased the activation of extracellular signal-regulated kinase-1/2 (ERK1/2), AKT and matrix metalloproteinase 9 (MMP9), and inhibited the motility in the SKOV3-MUC4 cells. Upon in vivo tumorigenesis and metastasis analysis, the SKOV3-MUC4 cells produced significantly larger tumors and demonstrated a higher incidence of metastasis to distance organs (peritoneal wall, colon, intestine, stomach, lymph nodes, liver and diaphragm). Taken together, our study reveals a novel role for MUC4 in inducing EMT through the upregulation of N-cadherin and promoting metastasis of OC cells.

MUC4 Mucin Interacts with and Stabilizes the HER2 Oncoprotein in Human Pancreatic Cancer Cells

MUC4, a high-molecular weight transmembrane glycoprotein, is overexpressed in pancreatic cancer and is implicated in its pathogenesis. It is a heterodimeric protein containing a large extracellular, heavily glycosylated subunit, MUC4alpha, and a transmembrane growth factor-like subunit, MUC4beta. In the present study, we have shown the interaction of human MUC4 with the receptor tyrosine kinase HER2 in pancreatic adenocarcinoma cells by reciprocal coimmunoprecipitation and cocapping studies. MUC4 colocalized with HER2 at the cell surface and in the cytoplasm. Silencing of MUC4 by transient or stable expression of MUC4-targeted short-interfering RNA led to the down-regulation of HER2 with a concomitant decrease in its phosphorylated form (pY(1248)-HER2). Further analyses revealed that the MUC4-knockdown-mediated decrease in HER2 expression occurred due to the drop in the stability of the receptor. In MUC4-knockdown pancreatic cancer cells, we also observed a reduced phosphorylation of the focal adhesion kinase and p42/44 mitogen-activated protein kinase, which are downstream effector proteins in HER2 signaling. Our findings add a new dimension to MUC4 function as a modulator of cell signaling and provide mechanistic evidence for its role in pancreatic cancer progression.

Mucins in the pathogenesis of breast cancer: Implications in diagnosis, prognosis and therapy

Mucins are high molecular weight, multifunctional glycoproteins comprised of two structural classes-the large transmembrane mucins and the gel-forming or secreted mucins. The primary function of mucins is to protect and lubricate the luminal surfaces of epithelium-lined ducts in the human body. Recent studies have identified a differential expression of both membrane bound (MUC1, MUC4 and MUC16) and secreted mucins (MUC2, MUC5AC, MUC5B and MUC6) in breast cancer tissues when compared with the non-neoplastic breast tissues. Functional studies have also uncovered many unique roles of mucins during the progression of breast cancer, which include modulation in proliferative, invasive and metastatic potential of tumor cells. Mucins function through many unique domains that can form complex association with various signaling molecules including growth factor receptors and intercellular adhesion molecules. While there is growing information about mucins in various malignancies including breast cancer, no focused review is there on the expression and functional roles of mucins in breast cancer. In this present review, we have discussed the differential expression and functional roles of mucins in breast cancer. The potential of mucins as diagnostic and prognostic markers and as therapeutic targets in breast cancer have also been discussed.

Transcriptional profiling of peripheral blood mononuclear cells in pancreatic cancer patients identifies novel genes with potential diagnostic utility

Background It is well known that many malignancies, including pancreatic cancer (PC), possess the ability to evade the immune system by indirectly downregulating the mononuclear cell machinery necessary to launch an effective immune response. This knowledge, in conjunction with the fact that the trancriptome of peripheral blood mononuclear cells has been shown to be altered in the context of many diseases, including renal cell carcinoma, lead us to study if any such alteration in gene expression exists in PC as it may have diagnostic utility. Methods and Findings PBMC samples from 26 PC patients and 33 matched healthy controls were analyzed by whole genome cDNA microarray. Three hundred eighty-three genes were found to be significantly different between PC and healthy controls, with 65 having at least a 1.5 fold change in expression. Pathway analysis revealed that many of these genes fell into pathways responsible for hematopoietic differentiation, cytokine signaling, and natural killer (NK) cell and CD8+ T-cell cytotoxic response. Unsupervised hierarchical clustering analysis identified an eight-gene predictor set, consisting of SSBP2, Ube2b-rs1, CA5B, F5, TBC1D8, ANXA3, ARG1, and ADAMTS20, that could distinguish PC patients from healthy controls with an accuracy of 79% in a blinded subset of samples from treatment naïve patients, giving a sensitivity of 83% and a specificity of 75%. Conclusions In summary, we report the first in-depth comparison of global gene expression profiles of PBMCs between PC patients and healthy controls. We have also identified a gene predictor set that can potentially be developed further for use in diagnostic algorithms in PC. Future directions of this research should include analysis of PBMC expression profiles in patients with chronic pancreatitis as well as increasing the number of early-stage patients to assess the utility of PBMCs in the early diagnosis of PC.

MUC16 induced rapid G2/M transition via interactions with JAK2 for increased proliferation and anti-apoptosis in breast cancer cells

MUC16/CA125 is a tumor marker currently used in clinics for the follow-up of patients with ovarian cancer. However, MUC16 expression is not entirely restricted to ovarian malignancies and has been reported in other cancers including breast cancer. Although it is well established as a biomarker, function of MUC16 in cancer remains to be elucidated. In the present study, we investigated the role of MUC16 in breast cancer and its underlying mechanisms. Interestingly, our results showed that MUC16 is overexpressed in breast cancer tissues whereas not expressed in non-neoplastic ducts. Further, stable knockdown of MUC16 in breast cancer cells (MDA MB 231 and HBL100) resulted in significant decrease in the rate of cell growth, tumorigenicity and increased apoptosis. In search of a mechanism for breast cancer cell proliferation we found that MUC16 interacts with the ezrin/radixin/moesin domain-containing protein of Janus kinase (JAK2) as demonstrated by the reciprocal immunoprecipitation method. These interactions mediate phosphorylation of STAT3 (Tyr705), which might be a potential mechanism for MUC16-induced proliferation of breast cancer cells by a subsequent co-transactivation of transcription factor c-Jun. Furthermore, silencing of MUC16 induced G2/M arrest in breast cancer cells through downregulation of Cyclin B1 and decreased phosphorylation of Aurora kinase A. This in turn led to enhanced apoptosis in the MUC16-knockdown breast cancer cells through Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated extrinsic apoptotic pathway with the help of c-Jun N-terminal kinase signaling. Collectively, our results suggest that MUC16 has a dual role in breast cancer cell proliferation by interacting with JAK2 and by inhibiting the apoptotic process through downregulation of TRAIL.

Pathobiological Implications of MUC16 Expression in Pancreatic Cancer

MUC16 (CA125) belongs to a family of high-molecular weight O-glycosylated proteins known as mucins. While MUC16 is well known as a biomarker in ovarian cancer, its expression pattern in pancreatic cancer (PC), the fourth leading cause of cancer related deaths in the United States, remains unknown. The aim of our study was to analyze the expression of MUC16 during the initiation, progression and metastasis of PC for possible implication in PC diagnosis, prognosis and therapy. In this study, a microarray containing tissues from healthy and PC patients was used to investigate the differential protein expression of MUC16 in PC. MUC16 mRNA levels were also measured by RT-PCR in the normal human pancreatic, pancreatitis, and PC tissues. To investigate its expression pattern during PC metastasis, tissue samples from the primary pancreatic tumor and metastases (from the same patient) in the lymph nodes, liver, lung and omentum from Stage IV PC patients were analyzed. To determine its association in the initiation of PC, tissues from PC patients containing pre-neoplastic lesions of varying grades were stained for MUC16. Finally, MUC16 expression was analyzed in 18 human PC cell lines. MUC16 is not expressed in the normal pancreatic ducts and is strongly upregulated in PC and detected in pancreatitis tissue. It is first detected in the high-grade pre-neoplastic lesions preceding invasive adenocarcinoma, suggesting that its upregulation is a late event during the initiation of this disease. MUC16 expression appears to be stronger in metastatic lesions when compared to the primary tumor, suggesting a role in PC metastasis. We have also identified PC cell lines that express MUC16, which can be used in future studies to elucidate its functional role in PC. Altogether, our results reveal that MUC16 expression is significantly increased in PC and could play a potential role in the progression of this disease.

Ossifying Fibromyxoid Tumor of Soft Parts: A Clinicopathologic, Proteomic and Genomic Study

Ossifying fibromyxoid tumor (OFMTs) of soft parts is a rare soft tissue and bone tumor of borderline malignancy displaying an uncertain line of differentiation. The existence of fully malignant OFMT is controversial. To better understand the natural history and line of differentiation taken by OFMT, we studied 46 cases by light microscopic, immunohistochemical (IHC), genomic, proteomic, and fluorescence in situ hybridization (FISH) methods. Cases were classified according to the 2003 Folpe and Weiss system. Clinical and follow-up information was obtained. IHC for S-100 protein, desmin, epithelial membrane antigen (EMA), cytokeratins, smooth muscle actin (SMA), INI-1, neurofilament protein (NFP), CD56d excitatory amino acid transporter-4 (EAAT4), and MUC4 was performed on formalin-fixed, paraffin-embedded (FFPE) tissues. Gene expression profiling and proteomic studies were conducted on FFPE tissues from 13 and 5 cases, respectively. FISH for INI-1 was performed on 10 cases. The 46 tumors arose in 29 men and 17 women (median age, 52 y; range 39 to 63 y) and involved the proximal (N=17) and distal extremities (N=13), head and neck (N=9), and trunk (N=5). Median tumor size was 5.4 cm (range, 1.0 to 21.0 cm). Cases were classified as typical OFMT (26 of 46, 57%), atypical OFMT (5 of 46, 11%), and malignant OFMT (15 of 46 cases, 32%). Clinical follow-up (27 cases, median 55 months’ duration) showed all patients with typical and atypical OFMT to be alive without disease. Adverse events, including 3 local recurrences, 3 metastases, and 3 deaths, were seen only in malignant OFMT. IHC results were as follows: S-100 protein (30 of 41, 73%), desmin (15 of 39, 38%), cytokeratin (4 of 35, 11%), EMA (5 of 32, 16%), SMA (2 of 34, 6%), INI-1 (lost in mosaic pattern in 14 of 19, 74%), EAAT4 (31 of 39, 80%), MUC4 (3 of 14, 21%), NFP (8 of 10, 80%) and CD56 (6 of 14, 43%). Gene expression profiling showed typical and malignant OFMTs to cluster together, distinct from schwannian tumors. Proteomic study showed expression of various collagens, S-100 protein, and neuron-related proteins. FISH showed INI-1 deletion in 5 of 7 (71%) cases. We conclude that malignant OFMTs exist and may be recognized by the previously proposed criteria of Folpe and Weiss. Expression of neuron-related markers, in addition to Schwann cell and cartilage-associated markers, suggests a “scrambled” phenotype in OFMTs. Loss of INI-1 or other genes on 22q is likely important in the pathogenesis of these rare tumors.