Abstract 5570: Laminin-5 gamma-2 (LAMC2) is highly expressed in anaplastic thyroid carcinoma and is associated with tumor progression, migration and invasion by modulating signaling of EGFR

Context: Anaplastic thyroid carcinoma (ATC) is an aggressive malignancy having no effective treatment. Laminin subunit gamma-2 (LAMC2) is an epithelial basement membrane protein involved in cell migration and tumour invasion and might represent an ideal target for the development of novel therapeutic approaches for ATC.

Objective: Study the role of LAMC2 in ATC tumorigenesis.

Design: LAMC2 expression was evaluated by RT-PCR, western blotting and immunohistochemistry in tumor specimens, adjacent non-cancerous tissues and cell lines. shRNA approach was used to investigate the effect of LAMC2 knockdown on tumorigenesis of ATC.

Results: LAMC2 was highly expressed in ATC samples and cell lines compared to normal thyroid tissues. Silencing LAMC2 by shRNA in ATC cells moderately inhibited cell growth in liquid culture and dramatically decreased growth in soft agar and in xenografts growing in immunodeficient mice. Silencing LAMC2 caused cell cycle arrest and significantly suppressed migration, invasion and wound healing of ATC cells. Rescue experiments by overexpressing LAMC2 in LAMC2 knockdown cells, reversed the inhibitory effects as shown by increased cell proliferation and colony formation. Microarray data demonstrated that LAMC2 shRNA significantly altered expression of genes associated with migration, invasion, proliferation and survival. Immunoprecipitation and co-localization experiments showed that LAMC2 bound to EGFR in ATC cells. Silencing LAMC2 partially blocked EGF-mediated activation of EGFR and its downstream pathway. Interestingly, cetuximab (EGFR blocking antibody) or EGFR siRNA additively enhanced the anti-proliferative activity of the LAMC2 knockdown ATC cells compared to control cells.

Conclusions: To our knowledge, this is the first report investigating the effect of LAMC2 on cell growth, cell cycle, migration, invasion and EGFR signaling in ATC cells, suggesting that LAMC2 may be a potential therapeutic target for treatment of ATC.

Citation Format: Manoj Garg, Deepika Kanojia, Ryoko Okamoto, Vikas Madan, Wenwen Chien, Abhishek Sampath, Ling-Wen Ding, Meng Xuan, Jonathan W Said, Ngan Doan, Li-Zhen Liu, Henry Yang, Sigal Gery, Gleen D Braunstein, H.Phillip Koeffler. Laminin-5 gamma-2 (LAMC2) is highly expressed in anaplastic thyroid carcinoma and is associated with tumor progression, migration and invasion by modulating signaling of EGFR. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5570. doi:10.1158/1538-7445.AM2014-5570

Abstract 4203: Overexpression of miR-26a-2 in human liposarcoma is correlated with poor patient survival

Approximately 90% of well-differentiated/de-differentiated LPS (WDLPS/DDLPS), the most common LPS subtype, have chromosomal amplification at 12q13-q15. Many protein-coding genes in the region, such as MDM2 and CDK4, have been studied as potential therapeutic targets for LPS treatment with minimal success. Within this amplicon near the MDM2 gene, our SNP array analysis identified frequent amplification of miR-26a-2. Besides being in the amplicon, we found that miR-26a-2 is overexpressed significantly in WDLPS/DDLPS, as well as in myxoid/round cell LPS (MRC). Furthermore, Kaplan-Meier survival analysis showed that overexpression of miR-26a-2 significantly correlated with poor patient survival in both types of LPS.

Based on these findings, we hypothesized that miR-26a-2 plays an important role in LPS tumorigenesis, regardless of LPS subtypes. Overexpression of miR-26a-2 in LPS cells could help the growth and survival of cancer cells in a cell type-specific manner, including faster cell proliferation, faster cell migration, enhanced clonogenicity, suppressed adipocyte differentiation, and/or resistance to apoptosis. Inhibition of miR-26a-2 in LPS cells using anti-miR-26a-2 resulted in the opposite responses.

To explain further the effect of miR-26a-2 overexpression in LPS cells, we performed in sillico analysis and identified 93 candidate targets of miR-26a-2. Among these candidate genes, we found that RCBTB1 (RCC1 and BTB domain containing protein 1) was located at 13q12.3-q14.3, a recurrent region of loss of heterozygosity (LOH) in human LPS. Indeed, overexpression of RCBTB1 made cells more susceptible to apoptosis. Likewise, inhibition of RCBTB1 made cells more resistant to apoptosis.

In conclusion, our study reveals, for the first time, the contribution that miR-26a-2 makes to LPS tumorigenesis, partly through inhibiting RCBTB1. Our study shows that miR-26a-2 is a novel therapeutic target for human LPS.

Citation Format: Dhong Hyun Tony Lee, Soroosh Amanat, Catherine Goff, Lawrence Weiss, Suzanne Cutter, Jonathan Said, Ngan Doan, Seishi Ogawa, Aiko Matsubara, Charles Forscher, H.Phillip Koeffler. Overexpression of miR-26a-2 in human liposarcoma is correlated with poor patient survival. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4203. doi:10.1158/1538-7445.AM2013-4203

T-antigen of sv40 blocks p53 transactivation but not p53 specific binding to DNA

The p53 is a DNA binding phosphoprotein that can act as a transcriptional activator through high affinity DNA binding sequences (HBS). The large T antigen (LT-ag) of SV40 virus can bind p53 and their association is considered important for transforming activities of the virus. In this study, we investigated the effects of LT-ag on transcriptional transactivating function of p53 using cotransfection assays and DNA-binding electrophoretic mobility shift assays. A reporter gene containing a minimal TK promoter and two copies of HBS for p53 was cotransfected with p53 and LT-ag expression vector into human SKOV3 cells (p53 non-expressor). The LT-ag inhibited in a dose-dependent fashion transactivation by wild-type p53. The LT-ag was unable to inhibit transactivation of a reporter gene containing a similar promoter (TK). The LT-ag mutants defective for binding to p53, failed to inhibit transactivation. The LT-ag inhibited the transactivation of a CAT reporter gene containing the GAL4-DNA recognition sequences by the p53 protein which was fused to the heterologous DNA binding domain (amino acids 1-147 of GAL4) in cotransfected cells showing that inhibition of p53 activities by LT-ag was not restricted to the p53 HBS-dependent reporter. LT-ag failed to inhibit GAL4-p53 fragment containing the transactivating, but non-LT-ag binding region of p53, showing the importance of LT-ag binding to p53 in order to restrict p53 transactivation. Immunohistochemical analysis showed that in SKOV3, nuclear localization of wild type p53 was unaffected by coexpressed LT-ag. Gel shift analysis determined that nuclear extract from cells cotransfected with p53 and LT-ag expression vectors contained p53 not associated with LT-ag; this free p53 was able to bind to the HBS. These results suggest that LT-ag of SV40 preferentially binds the transcriptionally active p53, preventing it from transactivating through p53-HBS; the transcriptionally inactive p53 in these cells can still bind p53-HBS.

Abstract 5119: Frequent splicing pathway mutations and aberrant RNA splicing in myelodysplasia

MDS are a group of myeloid neoplasms characterized by deregulated blood cell production and a high propensity to AML. Although a number of gene alterations have been implicated in the pathogenesis of MDS, they do not fully explain the pathogenesis of MDS. So, in order to clarify a comprehensive registry of gene mutations in MDS, we performed whole-exome sequencing of 29 cases with MDS and related myeloid neoplasm. A total of 268 somatic mutations or 9.2 mutations per sample were identified. Among these 9 genes were mutated in more than 2 cases, which not only included a spectrum of known gene targets in MDS, but also affected previously unknown genes that are commonly involved in RNA splicing pathway, including U2AF35, SRSF2 and ZRSR2. Together with additional three (SF3A1, SF3B1 and PRPF40B) found in single cases, 16 (55.2%) of the 29 discovery cases carried a mutation affecting the component of the splicing machinery. To confirm the observation, we examined 9 spliceosome genes for mutations in a large set of myeloid neoplasms. In total, 219 mutations were identified in 209 out of the 582 samples of myeloid neoplasms. RNA splicing pathway mutations were highly specific to myelodysplasia, including 19 of 23 (83%) cases with RARS, 43 of 50 (86%) RCMD-RS, 68 of 155 (44%) other MDS, 48 of 88 (55%) CMML, and 16 of 62 (26%) secondary AML with MDS features with a string preference of SF3B1 mutations to RARS and RCMD-RS and of SRSF2 to CMML, while they were rare in cases with de novo AML and MPN. Significantly, these mutations occurred in an almost completely mutually exclusive manner among mutated cases, suggesting the importance of deregulated RNA splicing in the pathogenesis of MDS. RNA splicing plays critical roles in differentiation, development, and disease and is a major source for protein diversity in higher eukaryotes. Splicing pathway mutations in myelodysplasia commonly affected those components of the splicing complex that are engaged in the 3′ splice site recognition, strongly indicating production of unspliced or aberrantly spliced RNA species are incriminated for the pathogenesis of MDS. So, to clarify the effect of these splicing mutations on RNA splicing, we expressed the wild-type and the mutant U2AF35 or SRSF2 in HeLa cells and performed whole transcriptome analysis in these cells. The results of exon array showed that the wild-type U2AF35 promoted RNA splicing correctly, whereas the mutant U2AF35 inhibited this processes and rendered intronic sequences to remain unspliced. RNA sequencing additionally showed that the number of reads that encompassed the exon/intron junctions was significantly increased in mutant U2AF35-transduced cells. This result means that mutant U2AF35 actually induced impaired 3′-splice site recognition during pre-mRNA processing. In conclusion, our study demonstrated that abnormal RNA splicing caused by mutations of multiple genes on RNA splicing pathway is a common feature of myelodysplasia.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5119. doi:1538-7445.AM2012-5119

Molecular analysis of INK4 genes in breast carcinomas

Cell cycle regulators have recently been implicated in oncogenic transformation of cells, including the cyclins active in the G1 phase of the cell cycle and their respective cyclin-dependent kinases (CDK) whose activities are regulated by a set of inhibitors of CDK (CDKI). Since CDKIs can inhibit cell proliferation, they may have a role as tumor suppressor genes. To determine if alterations of CDKI genes may be involved in tumorigenesis of breast cancer, we examined the mutational status of p16(INK4A), p15(INK4B), p18(INK4C), p19(INK4D) CDKI genes in 36 primary breast carcinomas and 9 breast cancer cell lines using polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP), direct DNA sequencing, and Southern blot analysis. Furthermore, amplification of cyclin D1, D2, D3 genes were also examined in these samples. One mutation of p15(INK4B) gene occurred, resulting in change of aspartic acid to asparagine at codon 85. Since aspartic acid at this position is conserved between all four human and murine INK4 proteins, this missense mutation may have functional significance. The sample with a p15(INK4B) point mutation was accompanied by amplification of the cyclin D1 gene. A deletion of the p18(INK4C) gene was found in a primary tumor. Three deletions of the p16(INK4A) gene and two deletions of the p15(INK4B) gene were found in the cell lines. Also, we found amplification of the p15(INK4B) and p16(INK4A) loci in a clinical sample as well as amplification of the p19(INK4D) in another sample, and amplification of the myeloperoxidase (MPO) gene in one cell line and two primary tumors. We suspect that a critical gene for breast cancer is amplified near the MPO gene. These data indicate that CDKI mutations are moderately rare in breast cancer and are often associated with the simultaneous alteration of more than one cell-cycle regulatory gene.

Mutational analysis of the hMSH2 gene in a wide variety of tumors

The hMSH2 gene participates in DNA mismatch repair and its mutation can result in genetic instability of the human genome which is an important feature of tumorigenesis. In this study, genetic alterations of the hMSH2 gene were examined in 43 ovarian, 36 non-small cell lung (NSCL), 31 poorly differentiated gastric, 15 endometrial, and 11 colon cancers, nine gastric cancer cell lines, 41 adult T-cell leukemias (ATLs), two ATL cell lines, and 37 non-Hodgkin's lymphomas (NHLs), using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) technique. Microsatellite instability (MSI) was also investigated for ovarian, NSCL, and colon cancers. The incidence of MSI was 1/36 (3%) for NSCL, 2/23 (9%) for ovarian, and 1/11 (9%) for colon cancers. Missense base changes of the hMSH2 gene were identified in two gastric cancer patients (ATG to ATA resulting in Met changing to Ile at codon 688 in exon 13 and ACA to GCA resulting in Thr changing to Ala at codon 803 in exon 14). These mutations were found in samples with no MSI. One ovarian and one gastric cancer, and six ATL samples showed two types of polymorphisms of hMSH2 (CTT to TTT resulting in Leu changing to Phe at codon 390 in exon 7 and CAG to AAG resulting in Gin to Arg at codon 419 in exon 7). Our data suggest that MSI and hMSH2 mutations are uncommon in sporadic tumors.

Potent tumoricidal effects of a human cytotoxic T-cell line (TALL-104) against prostate cancer

The human TALL-104 cell line possesses major histocompatibility complex non-restricted cytotoxic activity against a large variety of tumor targets. Adequate therapies for prostate cancer that has spread outside its capsule are lacking. In order to identify effective therapies for this problem, we investigated the antiproliferative effects of TALL-104 cells against three prostate cancer cell lines (LNCaP, PC-3, DU-145). A Cr-51-release: cytotoxicity assay showed that TALL-104 cells were very cytotoxic against the prostate cancer cells. For example, at a 1:1 ratio of TALL-104 cells to prostate cancer cells, the percent release of Cr-51 at 18 h were 50, 40, and 45% for LNCaP, PC-3, and DU-145, respectively. Analysis by inhibition of clonogenic growth of prostate cancer cells also showed that TALL-104 cells were extremely effective. For instance, a short-term (4 h or 18 h) pre-incubation of TALL-104 cells with these tumor cells at the effector to target ratio of 10:1 prior to clonogenic assay resulted in a substantial reduction in clonogenic tumor growth (90%, 65%, and 50% clonal growth inhibition for LNCaP, PC-3, and DU-145, respectively). Further experiments using both Cr-51 release and clonogenic assays showed that irradiated TALL-104 cells were also effective in their anti-prostatic cancer activities. We also examined if TALL-104 cells plus a chemotherapeutic agent might complement each other in their cytotoxic effects. Preincubation of prostate cancer cell targets with etoposide (0.2-20 mu g/ml) for 18 h markedly increased their susceptibility to TALL-104 lysis. The anti-tumor efficacy of TALL-104 cells was also demonstrated in vivo utilizing the BNX murine model engrafted with subcutaneous PC-3 prostate cancer cells. A substantial reduction in PC-3 tumor cell progression was observed in mice injected with irradiated TALL-104 cells (1x10(7) cells intraperitoneally or intratumorally for 5 days beginning on days 24 and 45 after implantation) as compared to mice injected with tumors only. Taken together, these findings suggest that TALL-104 cells may be utilized as a potent anti-tumor agent, either alone or in combination with other agents (such as etoposide) in metastatic prostate cancer.

DPC 4/SMAD 4 in non-pancreatic tumors with frequent LOH 18q21 and in hematological malignancies

Recently, a novel candidate tumor suppressor gene, DPC 4/SMAD 4, has been implicated in the development of pancreatic cancers. Its location at human chromosome 18q21 prompted us to investigate this gene in a large series of primary tumors located outside the gastrointestinal tract which have been associated with loss of heterozygocity (LOH) at this locus. One hundred and thirty primary solid tumor samples (28 breast, 34 non-small cell lung, and 20 prostate cancers, and 40 osteosarcomas), 32 cell lines as well as 162 leukemia and lymphoma cases were analysed by Southern blotting and PCR-SSCP for deletions and mutations of the DPC 4 gene. In the breast cancer cell line MDA-MB-468, the gene was found to be homozygously deleted. Neither the primary solid tumor samples nor hematological malignancies had detectable abnormalities. Our study suggests that alterations of the DPC 4 gene, unlike in pancreatic cancer, are rare in breast, nonsmall cell lung and prostate cancers, osteosarcomas and hematopoietic malignancies.