Myeloid STAT3 promotes formation of colitis-associated colorectal cancer in mice

Myeloid cells lacking STAT3 promote antitumor responses of NK and T cells but it is unknown if this crosstalk affects development of autochthonous tumors. We deleted STAT3 in murine myeloid cells (STAT3(Δm)) and examined the effect on the development of autochthonous colorectal cancers (CRCs). Formation of Azoxymethane/Dextransulfate (AOM/DSS)-induced CRCs was strongly suppressed in STAT3(Δm) mice. Gene expression profiling showed strong activation of T cells in the stroma of STAT3(Δm) CRCs. Moreover, STAT3(Δm) host mice were better able to control the growth of transplanted MC38 colorectal tumor cells which are known to be killed in a T cell-dependent manner. These data suggest that myeloid cells lacking STAT3 control formation of CRCs mainly via cross activation of T cells. Interestingly, the few CRCs that formed in STAT3(Δm) mice displayed enhanced stromalization but appeared normal in size indicating that they have acquired ways to escape enhanced tumor surveillance. We found that CRCs in STAT3(Δm) mice consistently activate STAT3 signaling which is implicated in immune evasion and might be a target to prevent tumor relapse

Autonomous inhibition of apoptosis correlates with responsiveness of colon carcinoma cell lines to ciglitazone.

Colorectal cancer is a leading cause of mortality worldwide. Resistance to therapy is common and often results in patients succumbing to the disease. The mechanisms of resistance are poorly understood. Cells basically have two possibilities to survive a treatment with potentially apoptosis-inducing substances. They can make use of their existing proteins to counteract the induced reactions or quickly upregulate protective factors to evade the apoptotic signal. To identify protein patterns involved in resistance to apoptosis, we studied two colorectal adenocarcinoma cell lines with different growth responses to low-molar concentrations of the thiazolidinedione Ciglitazone: HT29 cells underwent apoptosis, whereas SW480 cells increased cell number. Fluorescence detection and autoradiography scans of 2D-PAGE gels were performed in both cell lines to assess protein synthesis and turnover, respectively. To verify the data we performed shotgun analysis using the same treatment procedure as in 2D-experiments. Biological functions of the identified proteins were mainly associated with apoptosis regulation, chaperoning, intrinsic inflammation, and DNA repair. The present study suggests that different growth response of two colorectal carcinoma cell lines after treatment with Ciglitazone results from cell-specific protein synthesis and differences in protein regulation

Cell viability and mitochondrial membrane potential after treatment with thiazolidinediones.

<p>Cell viability was assessed by neutral red uptake in SW480 and HT29 cells treated with increasing concentrations of (A) Ciglitazone or (B) Troglitazone for 6 and 24 hours. *p<0.05, values of HT29 cells differ from those of SW480 cells. Mitochondrial membrane potential (Δψ_m) was assessed by JC-1 FACS analysis in (C) HT29 and (D) SW480 cells treated with increasing concentrations of Ciglitazone for 24 and 48 hours. *p<0.05, values at 48 hours differ from those at 24 hours. #p<0.05, values at indicated concentrations differ from baseline.</p

Cell responsiveness of colorectal adenocarcinoma cell lines after treatment with Ciglitazone.

<p>2D-PAGE gels were performed in (A) HT29 and (B) SW480 cells after treatment with 5 µM Ciglitazone. (1) Fluorescence scans of untreated cells, (2) fluorescence scans of cells treated with Ciglitazone, (3) autoradiography scans of untreated cells, (4) autoradiography scans of cells treated with Ciglitazone. Cell cycle distribution of (C) HT29 and (D) SW480 cells treated with increasing concentrations of Ciglitazone.</p

Protein synthesis in untreated colorectal adenocarcinoma cell lines.

<p>Representative 2D-PAGE gels of untreated (A) HT29 and (B) SW480 cells. Proteins synthesized to a greater extent in HT29 cells are indicated by hexagons, those in SW480 cells by circles. Accession numbers of proteins listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0114158#pone-0114158-t001" target="_blank">Table 1</a> are annotated according to the UniProtKB/Swiss-Prot database. (C) Total proteins identified by shotgun analysis in HT29 and SW480 cells.</p

STAT1 is a sex‐specific tumor suppressor in colitis‐associated colorectal cancer

The interferon‐inducible transcription factor STAT1 is a tumor suppressor in various malignancies. We investigated sex‐specific STAT1 functions in colitis and colitis‐associated colorectal cancer (CRC) using mice with specific STAT1 deletion in intestinal epithelial cells (STAT1∆IEC). Male but not female STAT1∆IEC mice were more resistant to DSS‐induced colitis than sex‐matched STAT1flox/flox controls and displayed reduced intraepithelial infiltration of CD8+ TCRαβ+ granzyme B+ T cells. Moreover, DSS treatment failed to induce expression of T‐cell‐attracting chemokines in intestinal epithelial cells of male but not of female STAT1∆IEC mice. Application of the AOM‐DSS protocol for induction of colitis‐associated CRC resulted in increased intestinal tumor load in male but not in female STAT1∆IEC mice. A sex‐specific stratification of human CRC patients corroborated the data obtained in mice and revealed that reduced tumor cell‐intrinsic nuclear STAT1 protein expression is a poor prognostic factor in men but not in women. These data demonstrate that epithelial STAT1 is a male‐specific tumor suppressor in CRC of mice and humans

Autonomous Inhibition of Apoptosis Correlates with Responsiveness of Colon Carcinoma Cell Lines to Ciglitazone

Colorectal cancer is a leading cause of mortality worldwide. Resistance to therapy is common and often results in patients succumbing to the disease. The mechanisms of resistance are poorly understood. Cells basically have two possibilities to survive a treatment with potentially apoptosis-inducing substances. They can make use of their existing proteins to counteract the induced reactions or quickly upregulate protective factors to evade the apoptotic signal. To identify protein patterns involved in resistance to apoptosis, we studied two colorectal adenocarcinoma cell lines with different growth responses to low-molar concentrations of the thiazolidinedione Ciglitazone: HT29 cells underwent apoptosis, whereas SW480 cells increased cell number. Fluorescence detection and autoradiography scans of 2D-PAGE gels were performed in both cell lines to assess protein synthesis and turnover, respectively. To verify the data we performed shotgun analysis using the same treatment procedure as in 2D-experiments. Biological functions of the identified proteins were mainly associated with apoptosis regulation, chaperoning, intrinsic inflammation, and DNA repair. The present study suggests that different growth response of two colorectal carcinoma cell lines after treatment with Ciglitazone results from cell-specific protein synthesis and differences in protein regulation