STAT4 expression and activation is increased during mitosis in vitro and in vivo in skin- and mucosa-derived cell types: implications in neoplastic and inflammatory skin diseases.

BACKGROUND: The signal transducer and activator of transcription-4 (STAT4/Stat4) is a transcription factor known to convey signals from interleukin-12, interleukin-23, and interferon-alpha/beta to the nucleus, resulting in activation of dendritic cells, T-helper cell differentiation and production of interferon-gamma. OBJECTIVE: To demonstrate a novel role for STAT4 in cell mitosis. RESULTS: Phosphoserine STAT4 (pSerSTAT4) is increased in cells undergoing mitosis and is distributed throughout the cytoplasm during this stage of the cell cycle, whilst phosphotyrosine STAT4 (pTyrSTAT4) is confined to the chromosomal compartment. This distinct pattern of pSerSTAT4 during mitosis is seen in vitro in human keratinocytes and in other cell types. This is also present in vivo in cells undergoing mitosis in normal skin, psoriasis and squamous cell carcinoma. Inhibition of STAT4 phosphorylation by lisofylline and depletion of STAT4 by RNA interference results in a delay in progression of mitosis and leads to a reduction in cells completing cytokinesis. CONCLUSION: Our data demonstrate that STAT4 plays a role in enabling the normal and timely division of cells undergoing mitosis.

Ets2 transcription factor in normal and neoplastic human breast tissue.

The Ets family of transcription factors regulate the expression of multiple genes involved in tumour formation and progression. The aim of this work was to test the hypothesis that the expression of Ets2 in breast cancers was associated with parameters of tumour progression and metastasis. Using reverse-transcriptase polymerase chain reaction (RT-PCR), Ets2 mRNA was detected in 69% of 181 breast carcinomas, 63% of 43 fibroadenomas and 47% of 43 specimens of normal breast tissue. Levels were significantly higher in carcinomas compared with normal breast tissue (P = 0.006). Using Western blotting, Ets2 protein was found to migrate as two bands with molecular masses of 52 kDa (p52) and 54kDa (p54). Levels of both proteins were significantly higher in the carcinomas compared with both fibroadenomas (P = 0.0001) and normal breast tissue (P = 0.0001). In the carcinomas, a significant relationship was found between the p52 and p54 form of Ets2 (r = 0.51, P < 0.0001; Spearman correlation). Also, in the carcinomas, a significant correlation was found between both forms of Ets2 protein and urokinase plasminogen activator (uPA) (for p52, r = 0.43, P = 0.0005, n = 68; for p54, r = 0.50, P = 0.0001, n = 68). As Ets2 binding sites are present on the uPA promoter, Ets2 may be one of the transcription factors regulating uPA expression in human breast cancer.

Overexpression of the Ets-1 transcription factor in human breast cancer.

The Ets family of transcription factors regulate expression of multiple genes involved in tumour progression. The aim of this study was to investigate the expression of Ets-1 in a large panel of human breast cancers and relate its levels to the parameters of tumour progression and metastasis. Using RT-PCR, Ets-1 mRNA was detected in 30 out of 42 (71%) fibroadenomas and 131 out of 179 (73%) primary breast carcinomas. Similarly, levels of Ets-1 mRNA were not significantly different in fibroadenomas and primary breast carcinomas. Using Western blotting, four forms of the Ets-1 protein were detected, that is, p33, p42, p51 and p52. Levels of both p51 and p52 but not p33 and p42 were present at significantly higher levels in the carcinomas compared to the fibroadenomas (for p51, P<0.007; for p52, P<0.02; Mann-Whitney U-test). Levels of p52, p51 and p33 correlated significantly with uPA protein levels (P<0.01), while only levels of p52 correlated significantly with HER-2/neu protein levels (P<0.01). Using immunohistochemistry, Ets-1 was found predominantly in tumour cells, but was also detected in some stromal cells surrounding tumour islands. We conclude that, while at the mRNA level, Ets-1 was found at similar levels in fibroadenomas and primary breast carcinomas, higher protein levels were detected in the cancers compared to the benign specimens. Since p52, p51 and p33 correlate with uPA levels, these forms of Ets-1 may play a role in breast cancer metastasis.