Nadia Kourda

Impaired Control of Effector T Cells by Regulatory T Cells: A Clue to Loss of Oral Tolerance and Autoimmunity in Celiac Disease?

OBJECTIVES:Regulatory T cells (Tregs) are instrumental for tolerance to self-antigens and dietary proteins. We have previously shown that interleukin (IL)-15, a cytokine overexpressed in the intestine of patients with celiac disease (CD), does not impair the generation of functional Tregs but renders human T cells resistant to Treg suppression. Treg numbers and responses of intestinal and peripheral T lymphocytes to suppression by Tregs were therefore compared in CD patients and controls.METHODS:Intraepithelial lymphocytes (IELs) and lamina propria lymphocytes (LPLs) were isolated from duodenal biopsy specimens of CD patients and controls. Concomitantly, CD4+CD25+ T lymphocytes (Tregs) were purified from blood. Responses of IELs and of LPLs, and peripheral lymphocytes (PBLs) to suppression by Tregs were tested by analyzing anti-CD3-induced proliferation and interferon (IFN)-γ production in the presence or absence of peripheral Tregs. Lamina propria and peripheral CD4+CD25+FOXP3+ T cells were assessed by flow cytometry.RESULTS:Although percentages of CD4+CD25+FOXP3+ LPLs were significantly increased in patients with active CD, proliferation and IFN-γ production of intestinal T lymphocytes were significantly less inhibited by autologous or heterologous Tregs in CD patients than in controls (P<0.01). In all tested CD patients, IEL were unable to respond to Tregs. Resistance of LPLs and PBLs to Treg suppression was observed in patients with villous atrophy who had significantly enhanced serum levels of IL-15 compared with patients without villous atrophy and controls.CONCLUSIONS:Our results indicate that effector T lymphocytes from active CD become resistant to suppression by Tregs. This resistance might cause loss of tolerance to gluten, but also to self-antigens.

Functional defects of peripheral regulatory T lymphocytes in patients with progressive vitiligo.

Auto‐reactive cytotoxic T lymphocytes play a key role in the progressive loss or destruction of melanocytes in vitiligo but the mechanism underlying the loss of self‐tolerance is unknown. A deregulation of regulatory T‐cell biology has recently been suggested. The analysis of the suppressive effects of peripheral T regulatory cells in vitiligo patients revealed a functional defect in seven of 15 cases. This defect was strongly correlated with disease activity. The evaluation of the percentage of peripheral regulatory T lymphocytes did not reveal any intrinsic quantitative defect. Yet, a decrease in the percentage of such cells was noted in patients with progressive forms, suggesting a recruitment of regulatory T cells from the peripheral blood to the site of injury. This was further corroborated by the significant increase of Forkhead box P3 expression in the vitiliginous skin of patients. Our data support the involvement of a functional defect of peripheral regulatory T cells in the pathogenesis of vitiligo and open new possibilities to advance therapeutic approaches.

A meta-analysis of the relationship between FGFR3 and TP53 mutations in bladder cancer.

TP53 and FGFR3 mutations are the most common mutations in bladder cancers. FGFR3 mutations are most frequent in low-grade low-stage tumours, whereas TP53 mutations are most frequent in high-grade high-stage tumours. Several studies have reported FGFR3 and TP53 mutations to be mutually exclusive events, whereas others have reported them to be independent. We carried out a meta-analysis of published findings for FGFR3 and TP53 mutations in bladder cancer (535 tumours, 6 publications) and additional unpublished data for 382 tumours. TP53 and FGFR3 mutations were not independent events for all tumours considered together (OR = 0.25 [0.18–0.37], p = 0.0001) or for pT1 tumours alone (OR = 0.47 [0.28–0.79], p = 0.0009). However, if the analysis was restricted to pTa tumours or to muscle-invasive tumours alone, FGFR3 and TP53 mutations were independent events (OR = 0.56 [0.23–1.36] (p = 0.12) and OR = 0.99 [0.37–2.7] (p = 0.35), respectively). After stratification of the tumours by stage and grade, no dependence was detected in the five tumour groups considered (pTaG1 and pTaG2 together, pTaG3, pT1G2, pT1G3, pT2-4). These differences in findings can be attributed to the putative existence of two different pathways of tumour progression in bladder cancer: the CIS pathway, in which FGFR3 mutations are rare, and the Ta pathway, in which FGFR3 mutations are frequent. TP53 mutations occur at the earliest stage of the CIS pathway, whereas they occur would much later in the Ta pathway, at the T1G3 or muscle-invasive stage.

Obesity and renal cancer: Role of adipokines in the tumor-immune system conflict

Epidemiological studies link obesity, as measured by increased body mass index (BMI) to the incidence of renal cell carcinoma (RCC) as well as to the cancer-related mortality of RCC patients. RCC is the third cancer most robustly associated with increased BMI. Understanding the role of the adipose tissue in renal carcinogenesis is therefore of major importance for the development of novel paradigms of RCC prevention and treatment. Here, we discuss the current knowledge on the impact of obesity on the development and progression of RCC as well as the role of adipose tissue-derived hormones (adipokines) in the conflict between growing tumors and the immune system.

Significant association between IL23R and IL17F polymorphisms and clinical features of colorectal cancer

Th17cells are involved in inflammatory and autoimmune diseases. These cells may be involved in pathological processes mainly producing pro-inflammatory cytokines. Recently, it was shown that the IL23/IL17 pathway plays an important role in the development of inflammatory bowel disease. In general, genes encoding cytokines are genetically polymorphic and polymorphisms in genes IL23R el IL17F were shown associated with susceptibility to Crohns disease and ulcerative colitis which in their turn are considered as risk factors for developing colorectal cancer (CRC). Our approach is to study IL17F and IL23R polymorphisms as risk factor associated with CRC in the Tunisian population in patients and healthy controls. Interesting, we noted a significant association between IL17F and IL23R polymorphisms and tumor location (p=0.0001 and p=0.049, respectively), tumor histology (p=0.007 and p=0.049, respectively) and tumor architecture (p=0.0000000001 and p=0.07, respectively) in CRC patients. We also showed a significant association of IL17F variant with an increased risk of TNM stage III/IV (p=0.007), showing an increased risk of advanced stage. Finally, we observed a positive link between IL17F polymorphism and CRC patients with lymph nodes (p=0.0000000001) and metastasis (p=0.00000009). However, we found no evidence to support a significant association between IL17F and IL23R polymorphisms and colorectal cancer susceptibility. Our findings suggest that IL17F and IL23R polymorphisms were significantly associated with clinical features variables. The IL17F cytokine appear to be involved in the control of tumor growth and invasion of gastrointestinal tumors. IL17 and IL23 polymorphisms or those of their receptors as important determinants of susceptibility to colorectal cancer are still subject to questioning.

Prognostic Value of Tumor-associated Macrophages Count in Human Non-muscle-invasive Bladder Cancer Treated by BCG Immunotherapy

Purpose: Tumor-associated macrophages can regulate the growth of various cancers positively or negatively. Intravesical bacillus Calmette-Guerin instillation is now the gold standard treatment for bladder carcinoma in situ. The authors investigated the correlation between tumor-associated macrophages infiltrating bladder carcinoma in situ and the response to intravesical bacillus Calmette-Guerin therapy. Materials and methods: The authors examined paraffin-embedded tissues from 41 patients with bladder carcinoma in situ who received intravesical bacillus Calmette-Guerin therapy. Tumor-associated macrophages were immunohistochemically stained by anti-CD68 monoclonal antibody. Results: The median number of tumor-associated macrophages infiltrating among cancer cells and the number in the lamina propria were 4 and 24, respectively. Recurrent carcinoma in situ was found in 4.8% of cases with a lower cancer cell tumor-associated macrophage count but in 47.6% of those with a higher cancer cell tumor-associated macrophage count (less than 4 vs. 4 or greater). Recurrence was found in 31.8% of patients with a lower lamina propria tumor-associated macrophage count but in 21.1% of those with a higher lamina propria tumor-associated macrophage count (less than 25 vs. 25 or greater). The median ratio of tumor-associated macrophages among cancer cells vs. in the lamina propria was 0.2. Recurrence-free survival was significantly better in patients with a lower cancer cell tumor-associated macrophage count (p = .0002). Those with a lower cancer cell-to-lamina propria tumor-associated macrophage ratio had a higher recurrence-free rate (p < .0001). Multivariate analysis revealed that the cancer cell tumor-associated macrophage count and the cancer cell-to-lamina propria tumor-associated macrophage ratio can be prognostic factors for bladder carcinoma in situ. Conclusions: The count of tumor-associated macrophages infiltrating the cancer area is useful for predicting the response of bladder carcinoma in situ to intravesical bacillus Calmette-Guerin instillation before treatment initiation. Although on univariate analysis TAMs are associated with other poor prognosticators, on multivariate analysis, TAMs appear only to be associated with MI and VI. TAMs may play a significant role in the biology of tumor progression of endometrial adenocarcinoma, but do not appear to be independent prognostic indicators of patient’s survival.

MicroRNAs 146a and 147b Biomarkers for Colorectal Tumor’s Localization

The recently identified class of microRNAs (miRs) provided a new insight into cancer research, since abnormalities of members of microRNAs family have been found in various types of cancer. However, the relationship between five miRNAs (miR146a, miR155, miR21, miR135a, and miR147b) and colorectal cancer remains unclear. In the present study, we examined expression of these miRNAs in 25 pair-matched colon cancer tissues and normal colon mucosa. The expression levels of miR146a, miR155, miR21, miR135a, and miR147b were quantified by real-time PCR. We found that miR21, miR146a, and miR135a were all expressed at higher levels in colon tumors. On the other hand, miR146a and miR147b expressions are significantly higher in left colon compared to right colon. These two miRs, especially miR146a, seemed to be markers for the left colon tumors. Moreover, significant proportional and inverse correlations were found between miR expressions in tumor and healthy tissue, and the correlations profiles were different depending on cancer localization. Taken together, these results lead us to suggest the presence of different mechanisms regulating miRs expression and consequently their target genes in left and right colon. So the pathway of colorectal carcinogenesis would be different according to the site of the tumor.

Positive link between variant Toll-like receptor 4 (Asp299Gly and Thr399Ile) and colorectal cancer patients with advanced stage and lymph node metastasis

Toll-like receptors (TLRs) are considered as major endotoxin-signaling receptor and as crucial sensors of innate immunity. TLRs recognize pathogen-associated molecular patterns; induce effectors genes involving inflammatory cytokines and therefore initiation of adaptative immune responses against pathogens. Recently, it has been shown that TLRs are involved in tumor progression. In fact, increased level of TLR4 is associated with progression of colon malignancies. Even, TLR4 polymorphism has been shown associated with susceptibility to have colorectal cancer. Our study aimed to investigate an association between TLR4 Asp299Gly (D299G) and Thr399Ile (T399I) polymorphisms in Tunisian patients with colorectal cancer. Using a primer extension method (SNaPshot), we genotyped two variants of TLR4 D299G and T399I in 100 patients with colorectal cancer and 140 healthy controls in Tunisian population. Interesting, we noted a significant association between T399I polymorphism and tumor differentiation (p = 0.027) and tumor architecture (p = 0.02) in colorectal cancer (CRC) patients. We also showed a significant association of D299G with an increased risk of advanced stage (p = 0.03). Finally, we observed a positive link between D299G and T399I polymorphisms and CRC patients with lymph node (p = 0.00024; p = 0.0005, respectively) and metastasis (p = 0.001; p = 0.002, respectively). However, we found no evidence to support a significant association between TLR4 D299G and T399I polymorphisms and colorectal cancer susceptibility. Our findings suggest that TLR4 D299G and T399I polymorphisms are significantly associated with clinical features variables. TLR4 polymorphisms may serve as biomarker of disease progression. Therefore, our results need confirmation in even larger studies.

Prevalence of mutations in APC, CTNNB1, and BRAF in Tunisian patients with sporadic colorectal cancer

Sporadic colorectal tumorigenesis is caused by alterations in the Wnt (APC, CTNNB1) and Ras pathways. Our objective was to analyze the occurrence of these genetic alterations in relation to tumor and patient characteristics. The prevalence of somatic alteration in the hot-spot regions of the APC, BRAF, and CTNNB1 genes was investigated in 48 unselected and unrelated Tunisian patients with sporadic colorectal cancer, and the association between the molecular features at these genes in relation to tumor and patient characteristics (age at diagnosis, sex, tumor localization, stage, and differentiation) was analyzed. Loss of heterozygosity was observed at the APC locus in 52% of the analyzed tumors. 6 novel mutations were detected by polymerase chain reaction sequencing in the mutation cluster region of the APC gene. No mutations were observed in the CTNNB1 gene in any tumor, but 8% of tumors harbored mutation in the BRAF gene. Clinicopathological analyses showed an association between APC point mutations and the earliest occurrence of sporadic colorectal cancer. The findings confirm the heterogeneity of APC gene alteration and also reveal a particular profile of this pathology among Tunisian patients that confirms the epidemiological data for this country.

Prognostic Value of Bcl-2 and Bax Tumor Cell Expression in Patients with Non Muscle-Invasive Bladder Cancer Receiving Bacillus Calmette-Guerin Immunotherapy

Apoptosis is the distinctive form of programmed cell death that complements cell proliferation in maintaining normal tissue homeostasis. The significance of constitutive apoptosis in the recurrence of Non Muscle Invasive Bladder Cancer has yet to be investigated. The aim of this study is to investigate the prognostic significance of Bax and Bcl-2 in terms of recurrence after BCG immunotherapy. Immunohistochemical analysis was performed on frozen biopsies to evaluate bcl-2 and Bax proteins expression in 28 cases of NMIBC. All patients with confirmed NMIBC were treated with intravesical BCG-immunotherapy. The follow up was performed for 26 months. The correlation between clinicopathological, immunohistochemical data and the response to BCG therapy was performed. Univariate analysis showed that, PT1 stage, High grade and Bax expression increased significantly the risk of recurrence (P = 0.015, P = 0.015 and P= 0.034 respectively). In addition, multivariate analysis selected the model involving stage, age, Bax and Bcl-2 expression as the best independent variables of recurrence. In conclusion, the expression of Bcl-2 and Bax in NMIBC could have a prognostic value in assessing the risk of recurrence after BCG immunotherapy. These findings require further investigations on larger cohort in order to ascertain new molecular markers of the response to BCG immunotherapy.