Tumor suppressor in lung cancer-1 (TSLC1) functions as a glioma tumor suppressor

The CADM1 tumor suppressor gene is a major candidate gene in MDS with deletion of the long arm of chromosome 11

Myelodysplastic syndromes (MDS) represent a heterogeneous group of clonal hematopoietic stem cell disorders characterized by ineffective hematopoiesis leading to peripheral cytopenias and in a substantial proportion of cases to acute myeloid leukemia. The deletion of the long arm of chromosome 11, del(11q), is a rare but recurrent clonal event in MDS. Here, we detail the largest series of 113 cases of MDS and myelodysplastic syndromes/myeloproliferative neoplasms (MDS/MPN) harboring a del(11q) analyzed at clinical, cytological, cytogenetic, and molecular levels. Female predominance, a survival prognosis similar to other MDS, a low monocyte count, and dysmegakaryopoiesis were the specific clinical and cytological features of del(11q) MDS. In most cases, del(11q) was isolated, primary and interstitial encompassing the 11q22-23 region containing ATM, KMT2A, and CBL genes. The common deleted region at 11q23.2 is centered on an intergenic region between CADM1 (also known as Tumor Suppressor in Lung Cancer 1) and NXPE2. CADM1 was expressed in all myeloid cells analyzed in contrast to NXPE2. At the functional level, the deletion of Cadm1 in murine Lineage-Sca1+Kit+ cells modifies the lymphoid-to-myeloid ratio in bone marrow, although not altering their multilineage hematopoietic reconstitution potential after syngenic transplantation. Together with the frequent simultaneous deletions of KMT2A, ATM, and CBL and mutations of ASXL1, SF3B1, and CBL, we show that CADM1 may be important in the physiopathology of the del(11q) MDS, extending its role as tumor-suppressor gene from solid tumors to hematopoietic malignancies.

A map of tumor-host interactions in glioma at single-cell resolution

BACKGROUND

Single-cell RNA sequencing is the reference technique for characterizing the heterogeneity of the tumor microenvironment. The composition of the various cell types making up the microenvironment can significantly affect the way in which the immune system activates cancer rejection mechanisms. Understanding the cross-talk signals between immune cells and cancer cells is of fundamental importance for the identification of immuno-oncology therapeutic targets.

RESULTS

We present a novel method, single-cell Tumor-Host Interaction tool (scTHI), to identify significantly activated ligand-receptor interactions across clusters of cells from single-cell RNA sequencing data. We apply our approach to uncover the ligand-receptor interactions in glioma using 6 publicly available human glioma datasets encompassing 57,060 gene expression profiles from 71 patients. By leveraging this large-scale collection we show that unexpected cross-talk partners are highly conserved across different datasets in the majority of the tumor samples. This suggests that shared cross-talk mechanisms exist in glioma.

CONCLUSIONS

Our results provide a complete map of the active tumor-host interaction pairs in glioma that can be therapeutically exploited to reduce the immunosuppressive action of the microenvironment in brain tumor.

The function and clinical relevance of lncRNA UBE2CP3-001 in human gliomas

INTRODUCTION

Gliomas are the most frequent primary tumors in the human brain. Recent studies have identified a class of long noncoding RNAs, named lncRNAs, which were reported to participate in regulating the development of various diseases, including gliomas. In our previous studies, we found that lncRNA UBE2CP3-001 was overexpressed in gliomas but not in normal tissue. However, the molecular functions of UBE2CP3-001 in glioma are largely unknown.

MATERIAL AND METHODS

The presence of UBE2CP3-001 in U87 cells, glioma tissues and normal brain tissues was detected by real-time RT-PCR. The ability of U87 cells to migrate was analyzed using a cellular wound healing assay after downregulation of UBE2CP3-001. The survival rate of U87 cells after UBE2CP3-001 knockdown was also analyzed using the CCK8 assay. In vivo tumor weights from xenograft tumors transfected with UBE2CP3-001 shRNA were further analyzed using in vivo animal experiments. The expression levels of MMP-9 and TRAF3IP2 were determined by Western blot.

RESULTS

Our data showed that UBE2CP3-001 was overexpressed in most glioma tissues (p < 0.01). Downregulation of UBE2CP3-001 could inhibit cell migration (p < 0.01) and invasiveness (p < 0.01) of U87 cells. Downregulation of UBE2CP3-001 in U87 cells also suppressed the cell proliferation (p < 0.01) and promoted apoptosis (p < 0.01). Furthermore, in vivo studies confirmed that knockdown of UBE2CP3-001 could retard the growth of U87 xenograft tumors (p < 0.01). Western blot analysis showed that knockdown of UBE2CP3-001 could effectively inhibit the expression of MMP-9 (p < 0.01) and TRAF3IP2 (p < 0.01) in U87 glioma cells.

CONCLUSIONS

These data suggest an important role of UBE2CP3-001 in glioma and indicate its potential application in anti-glioma therapy.

Tumor suppressor in lung cancer 1 (TSLC1), a novel tumor suppressor gene, is implicated in the regulation of proliferation, invasion, cell cycle, apoptosis, and tumorigenicity in cutaneous squamous cell carcinoma

Tumor suppressor in lung cancer 1 (TSLC1) is tightly implicated in a variety of biological processes and plays critical roles in tumor development and progression. However, the roles of TSLC1 in cutaneous squamous cell carcinoma (CSCC) remain to be unraveled. Here, we reported the TSLC1 gene that was significantly downregulated in CSCC tissues and cells, and survival times of patients with TSLC1 at a low level were markedly lower than that at a high level (P = 0.0070). A stepwise investigation demonstrated that an elevated TSLC1 level evoked obvious proliferation and invasion inhibitions and arrested cell cycle at G0/G1 phase in A431 cells. Moreover, increase of caspase-3 activity mediated by elevated TSLC1 level induced cell apoptosis in A431 cells. Most notably, upregulation of TSLC1 expression reduced the numbers of colony formation and tumorigenicity. Collectively, our results presented herein suggest that TSLC1 as tumor suppressor may play prominent roles in development and progression of CSCC via regulation of different biological processes.

Tumor suppressor TSLC1 is implicated in cell proliferation, invasion and apoptosis in laryngeal squamous cell carcinoma by regulating Akt signaling pathway

Overwhelming evidence has demonstrated that TSLC1 (tumor suppressor in lung cancer 1), a novel tumor suppressor, is crucially implicated in various biological processes including progression, proliferation and apoptosis during tumorigenesis. However, the exact functions and molecular details of TSLC1 in laryngeal cancer remain ill-defined. Here, the expression of TSLC1 in laryngeal squamous cell carcinoma (LSCC) tissues and cells was detected, and the biological roles of TSLC1 in LSCC cells were investigated. The results showed that expressions of TSLC1 mRNA and protein were significantly reduced in LSCC tissues with low expression in 18 of 85 (21.18 %) and 16 of 85 (18.82 %), respectively. Additionally, statistical analysis revealed a significant correlation of TSLC1 expression with TNM staging and lymph node metastases (P < 0.05), but not related to age, gender and tumor differentiation (P > 0.05). Elevation of TSLC1 level inhibited cell proliferation, reduced cell invasion in vitro and induced cell apoptosis in Hep-2 cells, most importantly, TSLC1 upregulation decreased the level of pAkt, but not changed the level of total Akt in Hep-2 cells. Stepwise investigations demonstrated that overexpression of TSLC1 in Hep-2 cells increased caspase-3 activity and expressions of bax and p21 proteins but decreased the levels of bcl-2, MMP-2 and MMP-9 proteins. These data suggest that TSLC1 may exert essential roles in the progression and development of LSCC, and thus TSLC1 may be a potential molecular target for LSCC treatment.

Function and histopathology of a cell adhesion molecule TSLC1 in cancer

Even less than a decade since the discovery of TSLC1, overwhelming evidence demonstrates that the loss of TSLC1 expression by methylation-mediated epigenetic silencing or LOH is crucially implicated in various processes during tumorigenesis. Here, we summarize TSLC1 function, highlighting the concept that TSLC1 mediates the formation of tumor suppressor network via its multidomain structure and bridges extracellular adhesive activity with intracellular signaling. Next, we focus on the histopathology of TSLC1 in various cancers and the association with clinicopathological characteristics. On the basis of these, we propose that TSLC1 represents a promising biomarker for cancer diagnosis and a potential target for cancer therapy.

11q21.1-11q23.3 Is a site of intrinsic genomic instability triggered by irradiation

The chromosome location, 11q21-23, is linked to loss of heterozygosity (LOH) in multiple tumors including those of breast, lung, and head and neck. To examine the process of LOH induction, the H292 cell line (human muco-epidermoid carcinoma) was irradiated or treated with anti-CD95 antibody, and individual clones isolated through two rounds of cloning. Regions of LOH were determined by screening a suite of eight polymorphic microsatellite markers covering 11p15-11q24 using fluorescent primers and genetic analyzer peak discrimination. LOH induction was observed extending through 11q21.1-11q23.3 in 6/49 of clones surviving 4 Gy and 8/50 after 8 Gy. Analysis of selected clones by Affymetrix 6.0 single nucleotide polymorphism (SNP) arrays confirmed the initial assessment indicating a consistent 27.3-27.7 Mbp deletion in multiple clones. The telomeric border of LOH mapped to a 1 Mbp region of elevated recombination. Whole genome analysis of SNP data indicated that site-restricted LOH also occurred across multiple additional genomic locations. These data indicate that 11q21.1-11q23.3, and potentially other regions of this cell line are sites of intrinsic cell-specific instability leading to LOH after irradiation. Such deletions may subsequently be propagated by genetic selection and clonal expansion.

Loss of NECL1, a novel tumor suppressor, can be restored in glioma by HDAC inhibitor-Trichostatin A through Sp1 binding site

Nectin-like molecule 1 (NECL1)/CADM3/IGSF4B/TSLL1/SynCAM3 is a neural tissue-specific immunoglobulin-like cell-cell adhesion molecule downregulated at the mRNA level in 12 human glioma cell lines. Here we found that the expression of NECL1 was lost in six glioma cell lines and 15 primary glioma tissues at both RNA and protein levels. Re-expression of NECL1 into glioma cell line U251 would repress cell proliferation in vitro by inducing cell cycle arrest. And also NECL1 could decrease the growth rate of tumors in nude mice in vivo. To further investigate the mechanism why NECL1 was silenced in glioma, the basic promoter region located at -271 to +81 in NECL1 genomic sequence was determined. DNA bisulfite sequencing was performed to study the methylation status of CpG islands in NECL1 promoter; however, no hypermethylated CpG site was found. Additionally, the activity of histone deacetylase (HDACs) in glioma was higher than that in normal brain tissues, and the expression of NECL1 in glioma cell lines could be reactivated by HDACs inhibitor-Trichostatin A (TSA). So the loss of NECL1 in glioma was at least partly caused by histone deacetylation. Luciferase reporter assays, chromatin immunoprecipitation and co-immunoprecipitation (co-IP) assays indicated that Sp1 played an important role in this process by binding to either HDAC1 in untreated glioma cells or p300/CBP in TSA treated cells. Our finding suggests that NECL1 may act as a tumor suppressor in glioma and loss of it in glioma may be caused by histone deacetylation.

Dispensable role of protein 4.1B/DAL-1 in rodent adrenal medulla regarding generation of pheochromocytoma and plasmalemmal localization of TSLC1

Protein 4.1B is a membrane skeletal protein expressed in various organs, and is associated with tumor suppressor in lung cancer-1 (TSLC1) in vitro. Although involvement of 4.1B in the intercellular junctions and tumor-suppression was suggested, some controversial results posed questions to the general tumor-suppressive function of 4.1B and its relation to TSLC1 in vivo. In this study, the expression of 4.1B and its interaction with TSLC1 were examined in rodent adrenal gland, and the involvement of 4.1B in tumorigenesis and the effect of 4.1B deficiency on TSLC1 distribution were also investigated using rodent pheochromocytoma and 4.1B-knockout mice. Although plasmalemmal immunolocalization of 4.1B was shown in chromaffin cells of rodent adrenal medulla, expression of 4.1B was maintained in developed pheochromocytoma, and morphological abnormality or pheochromocytoma generation could not be found in 4.1B-deficient mice. Furthermore, molecular interaction and colocalization of 4.1B and TSLC1 were observed in mouse adrenal gland, but the immunolocalization of TSLC1 along chromaffin cell membranes was not affected in the 4.1B-deficient mice. These results suggest that the function of 4.1B as tumor suppressor might significantly differ among organs and species, and that plasmalemmal retention of TSLC1 would be maintained by molecules other than 4.1B interacting in rodent chromaffin cells.

The neurofibromatosis 2 protein, merlin, regulates glial cell growth in an ErbB2- and Src-dependent manner

Individuals with the inherited cancer predisposition syndrome neurofibromatosis 2 (NF2) develop several central nervous system (CNS) malignancies, including glial cell neoplasms (ependymomas). Recent studies have suggested that the NF2 protein, merlin (or schwannomin), may regulate receptor tyrosine kinase signaling, intracellular mitogenic growth control pathways, or adherens junction organization in non-nervous-system cell types. For this report, we used glial fibrillary acidic protein conditional knockout mice and derivative glia to determine how merlin regulates CNS glial cell proliferation. We show that the loss of merlin in glial cells results in increased proliferation in vitro and in vivo. Merlin regulation of glial cell growth reflects deregulated Src activity, such that pharmacologic or genetic inhibition of Src activation reduces Nf2(-/-) glial cell growth to wild-type levels. We further show that Src regulates Nf2(-/-) glial cell growth by sequentially regulating FAK and paxillin phosphorylation/activity. Next, we demonstrate that Src activation results from merlin regulation of ErbB2 activation and that genetic or pharmacologic ErbB2 inhibition reduces Nf2(-/-) glial cell Src/Src effector activation and proliferation to wild-type levels. Lastly, we show that merlin competes with Src for direct binding to ErbB2 and present a novel molecular mechanism for merlin regulation of ErbB2-dependent Src signaling and growth control.

Expression and clinical significance of TSLC1 and DAL-1/4.1B in pancreatic cancer

AIM: To investigate the expression and clinicopathological significance of TSLC1 and DAL-1/4.1B proteins in pancreatic cancer.

METHODS: Immunohistochemical S-P method was used to measure the protein expression of TSLC1 and DAL-1/4.1B in 9 cases of normal pancreatic tissues, 11 cases of pancreatitis tissues and 42 cases of pancreatic cancer tissues, respectively.

RESULTS: The positive expression rates of TSLC1 and DAL-1/4.1B in pancreatic carcinoma were significantly lower than those in normal pancreatic tissues and pancreatitis tissues respectively (30.95% vs 77.78%, 81.82%; 28.57% vs 66.67%, 81.82%, P< 0.05 or 0.01). The expression levels of TSLC1 and DAL-1/4.1B in pancreatic cancer showed a significant correlation with the differentiation degree, lymph node metastasis and TNM staging (P < 0.05, respectively), but not with the gender, age, location or pathological typing. In 42 cases of pancreatic carcinoma, a significantly positive correlation was found between the expression of TSLC1 and DAL-1/4.1B proteins (r_s = 0.489, P < 0.01).

CONCLUSION: Down-regulated expression of TSLC1 and DAL-1/4.1B exist in pancreatic cancer, which are involved in the pathogenesis, development and metastasis of pancreatic cancer through TSLC1- DAL-1/4.1B cascade.

Merlin is a potent inhibitor of glioma growth

Neurofibromatosis 2 (NF2) is an inherited cancer syndrome in which affected individuals develop nervous system tumors, including schwannomas, meningiomas, and ependymomas. The NF2 protein merlin (or schwannomin) is a member of the Band 4.1 superfamily of proteins, which serve as linkers between transmembrane proteins and the actin cytoskeleton. In addition to mutational inactivation of the NF2 gene in NF2-associated tumors, mutations and loss of merlin expression have also been reported in other types of cancers. In the present study, we show that merlin expression is dramatically reduced in human malignant gliomas and that reexpression of functional merlin dramatically inhibits both subcutaneous and intracranial growth of human glioma cells in mice. We further show that merlin reexpression inhibits glioma cell proliferation and promotes apoptosis in vivo. Using microarray analysis, we identify altered expression of specific molecules that play key roles in cell proliferation, survival, and motility. These merlin-induced changes of gene expression were confirmed by real-time quantitative PCR, Western blotting, and functional assays. These results indicate that reexpression of merlin correlates with activation of mammalian sterile 20-like 1/2-large tumor suppressor 2 signaling pathway and inhibition of canonical and noncanonical Wnt signals. Collectively, our results show that merlin is a potent inhibitor of high-grade human glioma.