Malignant transformation of wild-type but not plasminogen activator inhibitor-1 gene-deficient fibroblasts decreases cellular sensitivity to chemotherapy-mediated apoptosis.

Plasminogen activator inhibitor-1 (PAI-1) inhibits the activation of the plasminogen activator system, the latter being involved in cancer growth and dissemination. Interestingly, PAI-1 is elevated in many solid tumours and this elevation has consistently been shown to be associated with shorter length of patient survival. This study aims to determine whether PAI-1 contributes to cancer cell growth by inhibiting apoptosis of tumour cells. It is shown that spontaneous transformation decreases cellular sensitivity to chemotherapy-mediated apoptosis of wild-type, but not PAI-1 gene-deficient, fibrosarcomas. PAI-1 gene-deficient and wild-type mice displayed similar sensitivity to treatment with etoposide, suggesting a differential effect of PAI-1 expression between cancer cells and normal cells. Thus, since PAI-1 appears to be an important factor in regulating apoptosis in cancer cells but not in normal cells, inhibitors of PAI-1 might be useful as sensitising pre-treatment for subsequent apoptosis-inducing anti-cancer therapy.

Establishment and characterization of models of chemotherapy resistance in colorectal cancer: Towards a predictive signature of chemoresistance.

Current standard treatments for metastatic colorectal cancer (CRC) are based on combination regimens with one of the two chemotherapeutic drugs, irinotecan or oxaliplatin. However, drug resistance frequently limits the clinical efficacy of these therapies. In order to gain new insights into mechanisms associated with chemoresistance, and departing from three distinct CRC cell models, we generated a panel of human colorectal cancer cell lines with acquired resistance to either oxaliplatin or irinotecan. We characterized the resistant cell line variants with regards to their drug resistance profile and transcriptome, and matched our results with datasets generated from relevant clinical material to derive putative resistance biomarkers. We found that the chemoresistant cell line variants had distinctive irinotecan- or oxaliplatin-specific resistance profiles, with non-reciprocal cross-resistance. Furthermore, we could identify several new, as well as some previously described, drug resistance-associated genes for each resistant cell line variant. Each chemoresistant cell line variant acquired a unique set of changes that may represent distinct functional subtypes of chemotherapy resistance. In addition, and given the potential implications for selection of subsequent treatment, we also performed an exploratory analysis, in relevant patient cohorts, of the predictive value of each of the specific genes identified in our cellular models.

The role of Serpine-1 and Tissue inhibitor of metalloproteinase type-1 in early host responses to Staphylococcus aureus intracutaneous infection of mice.

Staphylococcus aureus is a common cause of skin and soft tissue infections in animal and humans. In the current study, we hypothesized that early host responses to S. aureus infection leading to the recruitment of neutrophils and control of the bacterium at the site of infection depend on the expression of Serpine-1 and Tissue inhibitor of metalloproteinase type-1, two important endogenous proteinase inhibitors that possess regulatory properties on a variety of pathophysiological conditions. Using a mouse model of skin infection and single-gene and double-gene knockout mice, however, our observations showed that Serpine-1 and Tissue inhibitor of metalloprotease type-1 did not impact the number of bacteria accumulating at the site of infection. Double-gene knockout mice further had the same volume of accumulating host cells at the site of infection, while single Tissue inhibitor of metalloprotease type-1 knockout mice showed a decreased number of cells. Follow-up studies demonstrated changes in Serpine-1, Tissue inhibitor of metalloprotease type-1 and IL-6 plasma levels following challenge. In addition, double-gene knockout mice did not differ from wild-type mice in white blood cell, granulocyte and leucocyte counts, while single-gene genotypes differed in these phenotypes.

High expression of microRNA-625-3p is associated with poor response to first-line oxaliplatin based treatment of metastatic colorectal cancer.

The backbone of current cytotoxic treatment of metastatic colorectal cancer (mCRC) consists of a fluoropyrimidine together with either oxaliplatin (XELOX/FOLFOX) or irinotecan (XELIRI/FOLFIRI). With an overall objective response rate of approximately 50% for either treatment combination, a major unsolved problem is that no predictors of response to these treatments are available. To address this issue, we profiled 742 microRNAs in laser-capture microdissected cancer cells from responding and non-responding patients receiving XELOX/FOLFOX as first-line treatment for mCRC, and identified, among others, high expression of miR-625-3p, miR-181b and miR-27b to be associated with poor clinical response. In a validation cohort of 94 mCRC patients treated first-line with XELOX, high expression of miR-625-3p was confirmed to be associated with poor response (OR = 6.25, 95%CI [1.8; 21.0]). Independent analyses showed that miR-625-3p was not dysregulated between normal and cancer samples, nor was its expression associated with recurrence of stage II or III disease, indicating that miR-625-3p solely is a response marker. Finally, we also found that these miRNAs were up-regulated in oxaliplatin resistant HCT116/oxPt (miR-625-3p, miR-181b and miR-27b) and LoVo/oxPt (miR-181b) colon cancer cell lines as compared with their isogenic parental cells. Altogether, our results suggest an association between miR-625-3p and response to first-line oxaliplatin based chemotherapy of mCRC.

Plasminogen activator inhibitor 1 protects fibrosarcoma cells from etoposide-induced apoptosis through activation of the PI3K/Akt cell survival pathway.

High levels of plasminogen activator inhibitor (PAI-1) in tumors are associated with poor prognosis in several cancer types, and the reason for this association is not fully understood. Plasminogen activator inhibitor 1 has been suggested to contribute to tumor growth by protecting cancer cells from apoptosis, and we have previously shown that wild type murine fibrosarcoma cells are significantly more resistant to apoptosis induced by chemotherapy than PAI-1-deficient fibrosarcoma cells. Here, we further investigated the molecular mechanisms underlying the antiapoptotic function of PAI-1 focusing on the phosphatidylinositol 3-phosphate kinase (PI3K)/Akt cell survival pathway. We demonstrate that the activation level of the Akt cell survival pathway is reduced in PAI-1-deficient cells. Inhibition of either PI3K or Akt by synthetic inhibitors sensitized the wild type but not the PAI-1-deficient cells to etoposide-induced cell death. More importantly, reintroduction of PAI-1 expression in PAI-1-deficient cells induced an increase in Akt activity and protection against etoposide-induced apoptosis. Concordantly, silencing of PAI-1 by RNA interference in wild type fibrosarcoma cells decreased the level of active Akt, and this was accompanied by a sensitization of the cells to etoposide-induced cell death. Altogether, our data suggest that PAI-1 influences sensitivity to etoposide-induced apoptosis through the PI3K/Akt cell survival pathway by acting upstream of PI3K and Akt. This points to PAI-1 as a possible therapeutic target in cancer diseases where PAI-1 inhibits chemotherapy-induced apoptosis.