Cristina Largo

Genomic and expression profiling identifies the B‐cell associated tyrosine kinase Syk as a possible therapeutic target in mantle cell lymphoma

Among B‐cell lymphomas mantle cell lymphoma (MCL) has the worst prognosis. By using a combination of genomic and expression profiling (Affymetrix GeneChip Mapping 10k Xba131 and U133 set), we analysed 26 MCL samples to identify genes relevant to MCL pathogenesis and that could represent new therapeutic targets. Recurrent genomic deletions and gains were detected. Genes were identified as overexpressed in regions of DNA gain on 3q, 6p, 8q, 9q, 16p and 18q, including the cancer genes BCL2 and MYC. Among the transcripts with high correlation between DNA and RNA, we identified SYK, a tyrosine kinase involved in B‐cell receptor signalling. SYK was amplified at DNA level, as validated by fluorescence in situ hybridisation (FISH) analysis, and overexpressed at both RNA and protein levels in the JeKo‐1 cell line. Low‐level amplification, with protein overexpression of Syk was demonstrated by FISH in a small subset of clinical samples. After treatment with low doses of the Syk inhibitor piceatannol, cell proliferation arrest and apoptosis were induced in the cell line overexpressing Syk, while cells expressing low levels of Syk were much less sensitive. A combination of genomic and expression profiling suggested Syk inhibition as a new therapeutic strategy to be explored in lymphomas.

The SRY-HMG box gene, SOX4, is a target of gene amplification at chromosome 6p in lung cancer†

The search for oncogenes is becoming increasingly important in cancer genetics because they are suitable targets for therapeutic intervention. To identify novel oncogenes, activated by gene amplification, we analyzed cDNA microarrays by high-resolution comparative genome hybridization and compared DNA copy number and mRNA expression levels in lung cancer cell lines. We identified several amplicons (5p13, 6p22-21, 11q13, 17q21 and 19q13) that had a concomitant increase in gene expression. These regions were also found to be amplified in lung primary tumours. We mapped the boundaries and measured expression levels of genes within the chromosome 6p amplicon. The Sry-HMG box gene SOX4 (sex-determining region Y box 4), which encodes a transcription factor involved in embryonic cell differentiation, was overexpressed by a factor of 10 in cells with amplification relative to normal cells. SOX4 expression was also stronger in a fraction of lung primary tumours and lung cancer cell lines and was associated with the presence of gene amplification. We also found variants of SOX4 in lung primary tumours and cancer cell lines, including a somatic mutation that introduced a premature stop codon (S395X) at the serine-rich C-terminal domain. Although none of the variants increased the transactivation ability of SOX4, overexpression of the wildtype and of the non-truncated variants in NIH3T3 cells significantly increased the transforming ability of the weakly oncogenic RHOA-Q63L. In conclusion, our results show that, in lung cancer, SOX4 is overexpressed due to gene amplification and provide evidence of oncogenic properties of SOX4.

Release of Hypoacetylated and Trimethylated Histone H4 Is an Epigenetic Marker of Early Apoptosis

Nuclear events such as chromatin condensation, DNA cleavage at internucleosomal sites, and histone release from chromatin are recognized as hallmarks of apoptosis. However, there is no complete understanding of the molecular events underlying these changes. It is likely that epigenetic changes such as DNA methylation and histone modifications that are involved in chromatin dynamics and structure are also involved in the nuclear events described. In this report we have shown that apoptosis is associated with global DNA hypomethylation and histone deacetylation events in leukemia cells. Most importantly, we have observed a particular epigenetic signature for early apoptosis defined by a release of hypoacetylated and trimethylated histone H4 and internucleosomal fragmented DNA that is hypermethylated and originates from perinuclear heterochromatin. These findings provide one of the first links between apoptotic nuclear events and epigenetic markers.