Biomarkers and heterogeneous fibroblast phenotype associated with incisional hernia

Development of incisional hernia (IH) is multifactorial but inflammation and abdominal wall ECM (extracellular matrix) disorganization are key pathological events. We investigated if the differential expression of fibroblast biomarkers reflects the cellular milieu and the dysregulated ECM in IH tissues. Expression of fibroblast biomarkers, including connective tissue growth factor, alpha-smooth muscle actin (α-SMA), CD34 (cluster of differentiation 34), cadherin-11 and fibroblast specific protein 1 (FSP1), was examined by histology and immunofluorescence in the hernial-fascial ring/neck tissue (HRT) and hernia sack tissue (HST) harvested from the patients undergoing hernia surgery and compared with normal fascia (FT) and peritoneum (PT) harvested from brain-dead healthy subjects undergoing organ procurement for transplantation. The H&E staining revealed alterations in tissue architecture, fibroblast morphology, and ECM organization in the IH tissues compared to control. The biomarker for undifferentiated fibroblasts, CD34, was significantly higher in HST and decreased in HRT than the respective FT and PT controls. Also, the findings revealed an increased level of CTGF (connective tissue growth factor) with decrease in α-SMA in both HRT and HST compared to the controls. In addition, an increased level of FSP1 (fibroblast specific protein 1) and cadherin-11 in HRT with decreased level in HST were observed relative to the respective controls (FT and PT). Hence, these findings support the heterogeneity of fibroblast population at the laparotomy site that could contribute to the development of IH. Understanding the mechanisms causing the phenotype switch of these fibroblasts would open novel strategies to prevent the development of IH following laparotomy.

CDK2 is required for LMW-cyclin E mediated murine mammary tumorigenesis

Abstract #2007

Cyclin E is a regulatory protein with multiple functions that activates CDK2, controls centrosome duplication, and regulates histone gene transcription. Our previous studies have shown that the presence of Low-molecular-weight (LMW) forms of cyclin E correlates strongly with decreased survival in patients with breast cancer. Transgenic mice overexpressing LMW cyclin E had increased incidence of mammary tumors and distant metastasis when compared to full length cyclin E. The critical role of LMW cyclin E in mammary tumorigenesis may be the result of the ability of LMW cyclin E to bind and activate the cyclin-dependent kinase 2 (CDK2). To specifically test the importance of LMW cyclin E-associated CDK2 kinase activity in mammary tumorigenesis, we generated double and triple transgenic mice LMW cyclin E-T1;CDK2-/-, and LMW cyclin E-T1;p53+/-;CDK2-/-. We found that: (i) The development of the mammary glands proceeds relatively normally in these animals demonstrating that CDK2 kinase activity is largely dispensable for mammary gland development; (ii) These mice were resistant to breast cancers initiated by LMW cyclin E overexpression. Whereas LMW-cyclin E-T1 mice in CDK2+/- or CDK2+/+ background succumb to mammary tumors with mean latencies of 16 and 19.5 months respectively, their LMW cyclin E-T1; CDK2-/- littermates do not form mammary tumors up to 24 months (P=0.05 CDK2+/+ versus CDK2-/-; P=0.0252 CDK2+/- versus CDK2-/-; P=0.1457 CDK2+/+ versus CDK2+/-, Log rank test). Similarly, while MMTV-LMW cyclin E-T1/p53+/- transgenic mice in CDK2+/- or CDK2+/+ background succumb to mammary gland tumors between 7 and 13 months with 100% penetrance, their MMTV-LMW cyclin E-T1;p53+/-; CDK2-/- littermates are resistant to tumor formation (P<0.01 CDK2+/+ versus CDK2-/-; P=0.011 CDK2+/- versus CDK2-/-, P=0.5072 CDK2+/+ versus CDK2+/-, Log rank Test). In fact none of the CDK2-/- mice developed mammary tumors when crossed with cyclin E LMW transgenic mice. However, 2 out of the 12 MMTV-LMW cyclin E; p53+/-; CDK2-/- mice generated salivary gland tumors. Hence, these LMW cyclin E; p53+/-; CDK2-/- are susceptible to LMW cyclin E induced salivary tumors in the absence of CDK2. We concluded that CDK2 is critically required for LMW cyclin E induced mammary tumorigenesis and consequently, the loss of CDK2 renders CDK2-/- mice resistant to breast cancer induced by LMW cyclin E expression. In clear contrast to mammary epithelial cells, we found that in salivary gland cells LMW cyclin E continued to elicit malignant transformation even in the absence of CDK2. Our work suggests that due to the requirement of CDK2 for LMW-cyclin E mediated mammary tumorigeneis, these tumors are prime candidates for anti-CDK2 therapy.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2007.

CD45 modulates galectin-1-induced T cell death: regulation by expression of core 2 O-glycans

Galectin-1 induces death of immature thymocytes and activated T cells. Galectin-1 binds to T cell-surface glycoproteins CD45, CD43, and CD7, although the precise roles of each receptor in cell death are unknown. We have determined that CD45 can positively and negatively regulate galectin-1-induced T cell death, depending on the glycosylation status of the cells. CD45(+) BW5147 T cells lacking the core 2 beta-1,6-N-acetylglucosaminyltransferase (C2GnT) were resistant to galectin-1 death. The inhibitory effect of CD45 in C2GnT(-) cells appeared to require the CD45 cytoplasmic domain, because Rev1.1 cells expressing only CD45 transmembrane and extracellular domains were susceptible to galectin-1 death. Moreover, treatment with the phosphotyrosine-phosphatase inhibitor potassium bisperoxo(1,10-phenanthroline)oxovanadate(V) enhanced galectin-1 susceptibility of CD45(+) T cell lines, but had no effect on the death of CD45(-) T cells, indicating that the CD45 inhibitory effect involved the phosphatase domain. Expression of the C2GnT in CD45(+) T cell lines rendered the cells susceptible to galectin-1, while expression of the C2GnT in CD45(-) cells had no effect on galectin-1 susceptibility. When CD45(+) T cells bound to galectin-1 on murine thymic stromal cells, only C2GnT(+) T cells underwent death. On C2GnT(+) cells, CD45 and galectin-1 co-localized in patches on membrane blebs while no segregation of CD45 was seen on C2GnT(-) T cells, suggesting that oligosaccharide-mediated clustering of CD45 facilitated galectin-1-induced cell death.