Caspase-dependent proteolytic cleavage of STAT3alpha in ES cells, in mammary glands undergoing forced involution and in breast cancer cell lines.

BACKGROUND: The STAT (Signal Transducers and Activators of Transcription) transcription factor family mediates cellular responses to a wide range of cytokines. Activated STATs (particularly STAT3) are found in a range of cancers. Further, STAT3 has anti-apoptotic functions in a range of tumour cell lines. After observing a proteolytic cleavage in STAT3alpha close to a potential apoptotic caspase protease cleavage site we investigated whether STAT3alpha might be a caspase substrate. METHODS: STAT3alpha status was investigated in vitro in several cell systems:- HM-1 murine embryonic stem (ES) cells following various interventions; IOUD2 murine ES cells following induction to differentiate along neural or adipocyte lineages; and in a number of breast cancer cell lines. STAT3alpha status was also analysed in vivo in wild type murine mammary glands undergoing controlled, forced involution. RESULTS: Immunoblotting for STAT3alpha in HM-1 ES cell extracts detected amino and carboxy terminal species of approximately 48 kDa and 43 kDa respectively--which could be diminished dose-dependently by cell treatment with the nitric oxide (NO) donor drug sodium nitroprusside (SNP). UV irradiation of HM-1 ES cells triggered the STAT3alpha cleavage (close to a potential caspase protease cleavage site). Interestingly, the pan-caspase inhibitor z-Val-Ala-DL-Asp-fluoromethylketone (z-VAD-FMK) and the JAK2 tyrosine kinase inhibitor AG490 both inhibited cleavage dose-dependently, and cleavage was significantly lower in a heterozygous JAK2 knockout ES cell clone. STAT3alpha cleavage also occurred in vivo in normal murine mammary glands undergoing forced involution, coinciding with a pulse of phosphorylation of residue Y705 on full-length STAT3alpha. Cleavage also occurred during IOUD2 ES cell differentiation (most strikingly along the neural lineage) and in several human breast cancer cell lines, correlating strongly with Y705 phosphorylation. CONCLUSION: This study documents a proteolytic cleavage of STAT3alpha into 48 kDa amino and 43 kDa carboxyl terminal fragments in a range of cell types. STAT3alpha cleavage occurs close to a potential caspase site, and can be inhibited dose-dependently by SNP, AG490 and z-VAD-FMK. The cleavage seems to be caspase-dependent and requires the phosphorylation of STAT3alpha at the Y705 residue. This highly regulated STAT3alpha cleavage may play an important role in modulating STAT3 transcriptional activity.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

The Tumor-Immune Microenvironment and Response to Radiation Therapy

Chemotherapy and radiation therapy (RT) are standard therapeutic modalities for patients with cancer, including breast cancer. Historic studies examining tissue and cellular responses to RT have predominantly focused on damage caused to proliferating malignant cells leading to their death. However, there is increasing evidence that RT also leads to significant alterations in the tumor microenvironment, particularly with respect to effects on immune cells infiltrating tumors. This review focuses on tumor-associated immune cell responses following RT and discusses how immune responses may be modified to enhance durability and efficacy of RT

Consensus molecular subtype classification of colorectal adenomas

Consensus molecular subtyping is an RNA expression-based classification system for colorectal cancer (CRC). Genomic alterations accumulate during CRC pathogenesis, including the premalignant adenoma stage, leading to changes in RNA expression. Only a minority of adenomas progress to malignancies, a transition that is associated with specific DNA copy number aberrations or microsatellite instability (MSI). We aimed to investigate whether colorectal adenomas can already be stratified into consensus molecular subtype (CMS) classes, and whether specific CMS classes are related to the presence of specific DNA copy number aberrations associated with progression to malignancy. RNA sequencing was performed on 62 adenomas and 59 CRCs. MSI status was determined with polymerase chain reaction-based methodology. DNA copy number was assessed by low-coverage DNA sequencing (n = 30) or array-comparative genomic hybridisation (n = 32). Adenomas were classified into CMS classes together with CRCs from the study cohort and from The Cancer Genome Atlas (n = 556), by use of the established CMS classifier. As a result, 54 of 62 (87%) adenomas were classified according to the CMS. The CMS3 ‘metabolic subtype’, which was least common among CRCs, was most prevalent among adenomas (n = 45; 73%). One of the two adenomas showing MSI was classified as CMS1 (2%), the ‘MSI immune’ subtype. Eight adenomas (13%) were classified as the ‘canonical’ CMS2. No adenomas were classified as the ‘mesenchymal’ CMS4, consistent with the fact that adenomas lack invasion-associated stroma. The distribution of the CMS classes among adenomas was confirmed in an independent series. CMS3 was enriched with adenomas at low risk of progressing to CRC, whereas relatively more high-risk adenomas were observed in CMS2. We conclude that adenomas can be stratified into the CMS classes. Considering that CMS1 and CMS2 expression signatures may mark adenomas at increased risk of progression, the distribution of the CMS classes among adenomas is consistent with the proportion of adenomas expected to progress to CRC

Constitutive expression of human intercellular adhesion molecule-1 (ICAM-1) is regulated by differentially active enhancing and silencing elements

Contains fulltext : 22331___.PDF (publisher's version ) (Open Access

Avian erythroleukemia: a model for corepressor function in cancer

Contains fulltext : 112863.pdf (publisher's version ) (Closed access

Expression profiling of colon cancer cell lines and colon biopsies: towards a screening system for potential cancer-preventive compounds.

Contains fulltext : 48468.pdf (publisher's version ) (Closed access)Interest in mechanisms of colon cancer prevention by food compounds is strong and research in this area is often performed with cultured colon cancer cells. In order to assess utility for screening of potential cancer-preventive (food) compounds, expression profiles of 14 human cell lines derived from colonic tissue were measured using cDNA microarrays with 4000 genes and compared with expression profiles in biopsies of human colon tumours and normal tissue. Differences and similarities in the gene expression profiles of the cell lines were analysed by clustering and principal component analysis (PCA). Cytoskeleton genes and immune response genes are two functional classes of genes that contributed to the differences between the cell lines. A subset of 72 colon cancer-specific genes was identified by comparing expression profiles in human colon biopsies of tumour tissue and normal tissue. A separation of the cell lines based on the tumour stage of the original adenocarcinoma was observed after PCA of expression data of the subset of colon cancer-specific genes in the cell lines. The results of this study may be useful in the ongoing research into mechanisms of cancer prevention by dietary components