Krüppel-like factor 4 (KLF4) is expressed in a variety of tissues with diverse physiological functions and activities. KLF4 can also function as a tumor suppressor or an oncogene, depending on the cellular context. Its role in hematological malignancies is controversial. This study examined the expression levels of KLF4 by immunohistochemistry in 73 pediatric non-Hodgkin lymphomas (NHLs) in a tissue microarray and also on several B-NHL cell lines. Elevated levels of KLF4 expression were detected in 66% of lymphoma cases and were more frequent in the Burkitt lymphoma (p = 0.05) subtype. There was a significant predictive power for outcome with low KLF4 expression, predicting a favorable overall survival compared to high levels. Multivariate analyses confirmed the association of KLF4 expression with unfavorable overall survival (p < 0.005). These findings were consistent with analyses in existing NHL microarray datasets. The present findings revealed that KLF4 is overexpressed in Burkitt pediatric lymphoma and is a potential biomarker for inferior overall survival.

Multiple myeloma (MM) patients initially respond to conventional therapy, however, many develop resistance and have recurrences. We have reported in other tumors that the transcription factor Yin Yang 1 (YY1) is a resistant factor and, thus, we hypothesized that YY1 may be over-expressed in MM. Significantly, higher expression (staining intensity and cell frequency) of YY1 in MM cell lines and in bone marrow-derived (BM) MM from 22 MM patients was observed as compared to expression in normal BM. Higher nuclear YY1 staining was associated with disease progression. Bioinformatic analyses of mRNA in data sets corroborated the above findings and showed significant overexpression of YY1 in MM compared to normal tissues and other hematopoietic disorders. The role of YY1 expression in the regulation of drug resistance was exemplified in a drug-resistant MM cell line transfected with YY1 siRNA and which was shown to be sensitized to bortezomib-induced apoptosis. These findings highlight the potential prognostic significance of YY1 expression level in MM patients and as a therapeutic target.

Aim: To investigate the role of the transcription factor YY1 in Wilms tumor (WT). Patients & methods: We measured YY1 expression using tissue microarray from patients with pediatric renal tumors, mainly WT and evaluated correlations with the predicted clinical evolution. YY1 expression was measured using immunohistochemical and protein expression was determined by digital pathology. Results & conclusion: YY1 significantly increased in WT patients. In addition, an increase in YY1 expression had a greater risk of adverse outcomes in WT patients with favorable histology. YY1 expression was higher in the blastemal component of tumors, and high nuclear expression positively correlated with metastasis. YY1 may be considered as a metastasis risk factor in WT.

The Non-Hodgkin lymphomas are one of the most common of pediatric tumor, represent a group of curable tumors whose therapeutically success depends mainly in an early diagnosis, a combined therapy and a correct stratification according to prognosis factors. Several molecules have been reported as prognosis factors in cancer. However, some patients become refractory to such treatments. Alternative treatment modalities include immunotherapy, though, even in the presence of an effective anti-tumor response, the tumor develops mechanisms of resistance to apoptotic stimuli and cross-resistance to immune-mediated cytotoxicity. The transcription factor HIF-1 a (Hypoxia-inducible factor-1a) has been associated to the expression of different genes related to cancer (e.g SDF-1 and VEGF) and is considered as a prognostic factor in several types of cancers such as: leukemia, oropharyngeal cancer, neck cancer and ovarian carcinoma among others. However until now there is no clear evidence that the expression of HIF-1a is involve in the pathogenesis of pediatric Non-Hodgkin lymphomas. Hence, we hypothesized that one mechanism of pediatric Non-Hodgkin lymphomas immune escape may be due to overexpression of HIF-1a and VEGF. This hypothesis was tested using Tissue Microarrays (TMA) of formalin fixed, paraffin embedded sections of 70 untreated pediatric patients with different Non-Hodgkin lymphomas, obtained from the Children’s Mexican Hospital, Federico Gomez (Mexico, City). Cases included since 2000 to 2006, tumors were classified as: Burkitt lymphoma (BL, 19 cases), large B cell lymphoma (LBCL, 6 cases), lymphoblastic lymphoma (LL, 13 cases), anaplastic large cell lymphoma (ALCL, 12 cases), Hodgkin lymphoma (HL, 10 cases), and other type of lymphomas (10 cases). Staining by immunohistochemistry was performed to determine the expression levels of HIF-1a. The immunostaining was scored and both the percent of positive cells and the intensity were recorded and the data were analyzed statistically. Preliminary analyses show a very high cytoplasm and nuclear overexpression of HIF-1a in tumor tissue compared with the control (non tumor tissue or reactive hyperplasia). Quantitative analysis of HIF-1a expression among the different tumor tissue show a significant statistical difference (p=0.0124, ANOVA), results of Tukey analysis for reactive hyperplasia (RH) and tumor tissue were: RH vs LL p = 0.0001, RH vs LBCL p = 0.0148, RH vs ALCL p &lt; 0.04, RH vs BL p = 0.001, RH vs others p= 0.001. These studies suggest that overexpression of HIF-1 a may be involved in the pathogenesis of some pediatric Non-Hodgkin lymphomas (LL, LCGB, LCGA and BL) and is potential biomarker. Furthermore, inhibitors of HIF-1 a expression/activity may be targets for therapeutic intervention when combined with immunotherapy.

5184 Krüppel-like factor 4 (KLF4) is a transcription factor expressed in a variety of tissues in humans and has been implicated in several physiologic processes including development, differentiation, and tissue homeostasis. KLF4 is a bi-functional transcription factor that can either activate or repress transcription depending on the target gene. Human KLF4 is a protein of 470 amino acids with a 55 kDa. It contains three C-terminal C2H2-type zinc fingers that bind DNA. It is divided into three separate domains, namely, an N-terminal activation domain, a central repression domain and a C-terminal DNA-binding domain. For instance, KLF4 acts as a tumor suppressor gene in several cancers (colon, gastric, esophageal, bladder, and NSCLC) or as an oncogene (laryngeal carcinoma, squamous cell carcinoma, ductal carcinoma of the breast). However, the role of KLF4 in hematologic malignancies is still poorly understood. Reported studies in leukemia suggested that KLF4 may be a tumor suppressor. The goal of this study was to investigate the expression and the clinical significance of KLF4 in B-Non-Hodgkin's lymphomas (B-NHLs). Both B-NHL cell lines and patient-derived tumor tissues (TMA) were examined by western blot and immunohistochemistry, respectively. The expression of KLF4 was calculated based on the intensity and the percentage of the area stained, and scoring was corroborated by two pathologists. The complete absence of KLF4 expression was considered as KLF4 negative. Normal peripheral blood mononuclear cells expressed low levels of KLF4, in contrast, there was a significant overexpression of KLF4 in Ramos and Raji (Burkitt's lymphoma) and 2F7 (AIDS lymphoma) B-NHL cell lines. However, the DHL4 (DBLCL) cell line showed similar expression to normal cells. Among the 73 childhood lymphomas studied, 13/23 (57%) of lymphoblastic lymphoma, 7/20 (35%) of large B-cell lymphoma, 4/4 (100%) of anaplastic large cell lymphoma and 5/6 NHL not otherwise specified were KLF4 positive. Noteworthy, 18/18 (100%) Burkitt's lymphoma was KLF4 positive. In addition, the nuclear expression of KLF4 was significantly higher in Burkitt's lymphoma (n=18) compared to the remaining subtypes (lymphoblastic lymphoma, n=23, large B-cell lymphoma n=20 and others). All patients were treated with chemotherapy and the majority of the patients that were KLF4 positive had a stage 3–4 disease. Analysis of the EFS demonstrated that patients' tumors that were KLF4 negative had significantly higher EFS as compared to tumors that were KLF4 positive. Likewise, there was significant prolongation of survival in patients with tumors that were KLF4 negative. We suggest that the expression of KLF4 and poor response to chemotherapy may be attributed to its role in resistance via its regulation by the resistance factor Notch31. In contrast, the absence of KLF4 and good response to chemotherapy may be due to shifting p53 activity from cellular repair to cell death2. The present findings demonstrate that KLF4 may be considered as an oncogene in Burkitt's lymphoma and subsets of other types of lymphoma. The findings also suggest that the expression of KLF4 may be a potential prognostic factor, though, this need to be validated in a large cohort of patients. We propose that KLF4 may be a therapeutic target in patients with B-NHL lymphomas. Disclosures: No relevant conflicts of interest to declare.