Debora de Jong

BIC and miR-155 are highly expressed in Hodgkin, primary mediastinal and diffuse large B cell lymphomas.

In a previous study we demonstrated high expression of the non‐coding BIC gene in the vast majority of Hodgkins lymphomas (HLs). Evidence suggesting that BIC is a primary microRNA transcript containing the mature microRNA‐155 (miR‐155) as part of a RNA hairpin is now accumulating. We therefore analysed HL cell lines and tissue samples to determine whether miR‐155 is also expressed in HL. High levels of miR‐155 could be demonstrated, indicating that BIC is processed into a microRNA in HL. Most non‐HL subtypes were negative for BIC as determined by RNA‐ISH. However, in diffuse large B cell lymphoma (DLBCL) and primary mediastinal B cell lymphoma (PMBL), significant percentages of positive tumour cells were observed in 12/18 and 8/8 cases. A higher proportion of tumour cells were positive for BIC in DLBCL with activated B cell‐like phenotype than in DLBCL with germinal centre B cell‐like phenotype. Differential BIC expression was confirmed by qRT‐PCR analysis. Northern blot analysis showed expression of miR‐155 in all DLBCL and PMBL derived cell lines and tissue samples analysed. In summary, we demonstrate expression of primary microRNA BIC and its derivative miR‐155 in HL, PMBL and DLBCL. Copyright

High expression of B-cell receptor inducible gene BIC in all subtypes of Hodgkin lymphoma.

In a search for genes specifically expressed in Reed–Sternberg (RS) cells of Hodgkin lymphoma (HL), we applied the serial analysis of gene expression (SAGE) technique on the HL‐derived cell line DEV. Genes highly expressed in DEV were subjected to an RT‐PCR analysis to confirm the SAGE results. For one of the genes, a high expression was observed in DEV and other HL‐derived cell lines but not in non‐Hodgkin lymphoma (NHL)–derived cell lines and normal controls, suggesting an HL‐specific expression. This gene corresponds to the human BIC gene, a member of the noncoding mRNA‐like molecules. RNA in situ hybridization (ISH) indicated an exclusive nucleolar localization of BIC transcripts in all RS cells in 91% of HL cases, including nodular lymphocyte predominance (NLP) HL and classical HL. Analyses of normal human tissues revealed BIC transcripts in only a small number of CD20‐positive B‐cells in lymph node and tonsil tissue, albeit at a much lower level compared to that of RS cells. BIC RT‐PCR in the Burkitt lymphoma–derived cell line Ramos demonstrated a significant up‐regulation upon cross‐linking of the B‐cell receptor (BcR). IκBα‐mediated blocking of NF‐κB translocation in Ramos did not effect the up‐regulation of BIC expression upon BcR triggering, suggesting that activation of NF‐κB is not involved in regulation of BIC expression. In summary, our data show that expression of BIC is specific for RS cells of HL. In normal tissue, BIC is expressed weakly in a minority of germinal center B cells. Expression of BIC can be modified/influenced by BcR triggering, indicating that BIC might play a role in the selection of B cells.

Lack of BIC and microRNA miR-155 expression in primary cases of Burkitt lymphoma.

We previously demonstrated high expression of primary‐microRNA BIC (pri‐miR‐155) in Hodgkin lymphoma (HL) and lack of expression in most non‐Hodgkin lymphoma subtypes including some Burkitt lymphoma (BL) cases. Recently, high expression of BIC was reported in BL in comparison to pediatric leukemia and normal peripheral‐blood samples. In this study, we extended our series of BL cases and cell lines to examine expression of BIC using RNA in situ hybridization (ISH) and quantitative RT‐PCR (qRT‐PCR) and of miR‐155 using Northern blotting. Both BIC RNA ISH and qRT‐PCR revealed no or low levels of BIC in 25 BL tissue samples [including 7 Epstein–Barr virus (EBV)–positive cases] compared to HL and normal controls. In agreement with these findings, no miR‐155 was observed in BL tissues. EBV‐negative and EBV latency type I BL cell lines also showed very low BIC and miR‐155 expression levels as compared to HL cell lines. Higher levels of BIC and miR‐155 were detected in in vitro transformed lymphoblastoid EBV latency type III BL cell lines. An association of latency type III infection and induction of BIC was supported by consistent expression of BIC in 11 and miR‐155 in 2 posttransplantation lymphoproliferative disorder (PTLD) cases. In summary, we demonstrated that expression of BIC and miR‐155 is not a common finding in BL. Expression of BIC and miR‐155 in 3 latency type III EBV–positive BL cell lines and in all primary PTLD cases suggests a possible role for EBV latency type III specific proteins in the induction of BIC expression.

A novel human cDNA highly homologous to the fish hormone stanniocalcin

Stanniocalcin is a glycoprotein hormone previously considered present only in bony fish where it is secreted by the corpuscles of Stannius, endocrine organs involved in Ca2+ homeostasis. In fish, stanniocalcin was thought to be an adaptation for Ca2+ regulation in aquatic environments, and its effects include inhibition of gill Ca2+ transport. We have obtained a human cDNA clone coding for a protein highly homologous to fish stanniocalcin. The mRNA is expressed in many human tissues, with the highest levels in ovary, prostate and thyroid. In vitro human cell culture studies show that the mRNA is positively regulated by extracellular Ca2+ in the medium. We conclude that a human protein similar to the fish hormone is expressed in multiple tissues rather than by a specialized endocrine organ.

Determination of TP53 Mutation Is More Relevant Than Microsatellite Instability Status for the Prediction of Disease-Free Survival in Adjuvant-Treated Stage III Colon Cancer Patients

PURPOSE Microsatellite instability (MSI), TP53 mutation, and KRAS mutation status have been reported as prognostic factors in colon cancer. Most studies, however, have included heterogeneous groups of patients with respect to cancer stage. We determined the prognostic relevance of high-frequency MSI (MSI-H), TP53 mutations, and KRAS mutations in a well-defined group of patients with stage III colon cancer (N = 391), randomly assigned for adjuvant treatment with fluorouracil-based chemotherapy. METHODS Three hundred ninety-one tumor specimens were available. MSI was determined in 273 specimens, and mutation analyses of TP53 and KRAS were performed in 220 and 205 specimens, respectively. RESULTS In a univariate analysis, MSI-H (44 of 273; 16%) was associated with a longer disease-free survival (DFS; P = .038), but in a multivariate model adjusting for nodal involvement, histology, invasion, and grade of tumor, the association of MSI status with DFS did no longer reach statistical significance, though the risk estimate for microsatellite stability versus MSI-H tumors did not change much. Mutant TP53, found in 116 (53%) of 220 tumors, was associated with a shorter DFS, both in univariate (P = .009) and multivariate analyses (P = .018), whereas KRAS mutations (58 of 205; 28%) did not show any prognostic significance. CONCLUSION Both mutant TP53 and MSI-H seem to be prognostic indicators for disease-free survival, but only TP53 retains statistical significance after adjusting for clinical heterogeneity. Thus, in adjuvantly treated patients with stage III colon cancer, presence or absence of a TP53 mutation should be considered as a better predictor for DFS than MSI status.

A high throughput experimental approach to identify miRNA targets in human cells

The study of human microRNAs is seriously hampered by the lack of proper tools allowing genome-wide identification of miRNA targets. We performed Ribonucleoprotein ImmunoPrecipitation—gene Chip (RIP-Chip) using antibodies against wild-type human Ago2 in untreated Hodgkin lymphoma (HL) cell lines. Ten to thirty percent of the gene transcripts from the genome were enriched in the Ago2-IP fraction of untreated cells, representing the HL miRNA-targetome. In silico analysis indicated that ∼40% of these gene transcripts represent targets of the abundantly co-expressed miRNAs. To identify targets of miR-17/20/93/106, RIP-Chip with anti-miR-17/20/93/106 treated cells was performed and 1189 gene transcripts were identified. These genes were analyzed for miR-17/20/93/106 target sites in the 5′-UTRs, coding regions and 3′-UTRs. Fifty-one percent of them had miR-17/20/93/106 target sites in the 3′-UTR while 19% of them were predicted miR-17/20/93/106 targets by TargetScan. Luciferase reporter assay confirmed targeting of miR-17/20/93/106 to the 3′-UTRs of 8 out of 10 genes. In conclusion, we report a method which can establish the miRNA-targetome in untreated human cells and identify miRNA specific targets in a high throughput manner. This approach is applicable to identify miRNA targets in any human tissue sample or purified cell population in an unbiased and physiologically relevant manner.

Major role for a 3p21 region and lack of involvement of the t(3;8) breakpoint region in the development of renal cell carcinoma suggested by loss of heterozygosity analysis

In a loss of heterozygosity analysis of 3p, we examined 44 sporadic cases of renal cell carcinoma (RCC) and matched normal tissue with 18 markers distributed over the whole p‐arm. The majority of these markers clustered in three regions that have been suggested to be involved in the development of RCC, namely the p25 region, where the Von Hippel Lindau (VHL) gene is located; the p21 region, which has been identified as a common region of overlap (SRO) of heterozygous deletions; and the p14 region, which is the location of the constitutional t(3;8) breakpoint occurring in an RCC family. Thirty‐one out of these 44 tumors were analyzed with 9 additional markers from the 3p12‐14 region to further delimit the SRO in this region. Our analysis shows that when deletions were detected the 3p21 region was always included. The 3p21 markers D3F1552 and UBEIL were always contained within these 3p21 deletions. The t(3;8) breakpoint region showed the lowest percentage of loss of heterozygosity. Moreover, in three cases the t(3;8) breakpoint region retained heterozygosity, whereas a region more proximal to the breakpoint showed allelic losses. This supports exclusion of the t(3;8) region from a role in the development of sporadic RCC. In a number of tumors, two or three 3p regions with allelic losses were present separated by a region of retention of heterozygosity. In these tumors deletions at 3p21 occurred in combination with deletions of either the VHL region, or the region proximal to the t(3;8), or both, suggestive of multiple gene involvement in the development of sporadic RCC with a primary role of the 3p21 region. Genes Chromosom Cancer 14:00–00 (1995).

Low Frequency of FAS Mutations in Reed-Sternberg Cells of Hodgkin’s Lymphoma

Reed-Sternberg (RS) cells, the neoplastic elements of Hodgkins lymphoma (HL), usually lack B-cell receptor expression. Normal germinal center B cells, with lack of or low-affinity B-cell receptor expression, are eliminated via FAS-induced apoptosis. RS cells express FAS, but are rescued from apoptosis by a transforming event. It is known that HL-derived cell lines are resistant to FAS-mediated apoptosis. To investigate potential causes for this resistance, FAS mutations and c-FLIP expression were studied in four HL-derived cell lines and 20 cases of HL. L1236 was found to have a splice donor site mutation in intron 7 that resulted in an aberrantly spliced FAS transcript. Screening of microdissected RS cells revealed loss of heterozygosity for a known exon 7 polymorphism in two of six informative cases indicating loss of one FAS allele. In one of the two cases with loss of heterozygosity a hemizygous mutation was detected in exon 9. c-FLIP expression was observed in all HL cell lines and in RS cells of all HL cases. Our data show that FAS mutations are rare and suggest that overexpression of c-FLIP, which was present in all cases, is involved in the resistance to FAS-mediated apoptosis.

MiR-17/106b seed family regulates p21 in Hodgkin's lymphoma

Hodgkins lymphoma (HL) is a B cell‐derived lymphoma characterized by a minority of malignant Hodgkin Reed–Sternberg (HRS) cells that have lost their normal B cell phenotype. Alterations in the cell cycle and apoptosis pathways might contribute to their resistance to apoptosis and sustained cell cycle progression. A key player in both cell cycle arrest and apoptosis is CDKN1A, encoding p21

Long noncoding RNAs as a novel component of the Myc transcriptional network

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