The C-Terminal Acidic Tail Modulates the Anticancer Properties of HMGB1.

Energy metabolism reprogramming was recently listed as a hallmark of cancer. In this process, the switch from pyruvate kinase isoenzyme type M1 to pyruvate kinase isoenzyme type M2 (PKM2) is believed to play a crucial role. Interestingly, the activity of the active form of PKM2 can efficiently be inhibited by the high-mobility group box 1 (HMGB1) protein, leading to a rapid blockage of glucose-dependent aerobic respiration and cancer cell death. HMGB1 is a member of the HMG protein family. It contains two DNA-binding HMG-box domains and an acidic C-terminal tail capable of positively or negatively modulating its biological properties. In this work, we report that the deletion of the C-terminal tail of HMGB1 increases its activity towards a large panel of cancer cells without affecting the viability of normal immortalized fibroblasts. Moreover, in silico analysis suggests that the truncated form of HMGB1 retains the capacity of the full-length protein to interact with PKM2. However, based on the capacity of the cells to circumvent oxidative phosphorylation inhibition, we were able to identify either a cytotoxic or cytostatic effect of the proteins. Together, our study provides new insights in the characterization of the anticancer activity of HMGB1.

miR-17-92 cluster components analysis in Burkitt lymphoma: overexpression of miR-17 is associated with poor prognosis.

Burkitt lymphoma (BL) is an aggressive B cell lymphoma characterized by the reciprocal translocation of the c-Myc gene with immunoglobulin genes. Recently, MYC has been shown to maintain the neoplastic state via the miR-17-92 microRNA cluster that suppresses chromatin regulatory genes and the apoptosis regulator Bim. However, the expression and prognostic impact of miR-17-92 members in pediatric BL (pBL) are unknown. Therefore, we investigated miR-17, miR-19a, miR-19b, miR-20, and miR-92a expression and prognostic impact in a series of 41 pBL samples. In addition, Bim protein expression was evaluated and compared to miR-17, miR-19a, miR-19b, miR-20, and miR-92a levels and patient outcomes. The expression of miR-17-92 members was evaluated by qPCR and Bim protein by immunohistochemistry. Log-rank test was employed to assess prognostic impact. We found that upregulated expression of miR-17 and miR-20a correlates with lack of pro-apoptotic Bim expression. Patients bearing tumors with upregulated miR-17 displayed decreased overall survival (OS), and multivariate analysis revealed that miR-17 was a significant predictor of shortened OS. Using hairpin inhibitors, we showed that inhibition of miR-17 resulted in enhanced Bim expression in a BL cell line overexpressing the miR-17-92 cluster. Our results describe for the first time miR-17, miR-19a, miR-19b, miR-20a, and miR-92a expression profiles in pBL. The prognostic impact of miR-17 should be validated in a larger series, and may provide new therapeutic avenues in the era of anti-miRNA therapy research. Additional functional studies are further required to understand the specific role of miR-17-92 cluster members in BL.

Centroblastic diffuse large B cell lymphoma displays distinct expression pattern and prognostic role of apoptosis resistance related proteins.

Centroblastic diffuse large B cell lymphoma (DLBCL) samples were analyzed by immunohistochemistry to evaluate the expression of p53, Bcl-2, Survivin, XIAP, and Ki-67. Survivin was the only protein which expression exhibited a trend for impact in progression-free (p = .077) and overall survival (p = .054). In the Mann-Whitney test, Survivin expression correlated with a negative overall survival (p = .045). These results appeared to be intimately related to Survivin cytoplasmic localization. Moreover, the anti-apoptotic proteins Bcl-2 and Survivin were less frequent in centroblastic DLBCL. Our results indicate that centroblastic DLBCL may be a disease with characteristic biology and clinical course and, therefore, specific prognostic factors.

p53 expression and subcellular survivin localization improve the diagnosis and prognosis of patients with diffuse astrocytic tumors.

PURPOSE: Diffuse astrocytic tumors are the most frequently occurring primary central nervous system (CNS) tumors. Their histological sub-classification into diffuse astrocytoma (DA), anaplastic astrocytoma (AA) and glioblastoma (GB) is challenging and the available prognostic factors are limited to age and tumor subtype. Biomarkers that may improve the histological sub-classification and/or serve as prognostic factors are, therefore, urgently needed. The relationship between survivin and p53 in diffuse astrocytic tumor progression and survival is currently unclear. Here, we aimed to assess the relevance of these proteins in the accuracy of the histological sub-classification of these tumors and their respective treatment responses. METHODS: One hundred and thirty-three formalin-fixed paraffin-embedded diffuse astrocytic tumor samples were included. The tumor samples were histologically reviewed and subsequently assessed for p53 and survivin expression and the presence of the IDH R132H mutation by immunohistochemistry. p53 expression levels and survivin subcellular localization patterns were correlated with histological classification and clinical outcome. RESULTS: We found that age and histological subtype were the only features with a prognostic impact. In addition, we found that high p53 expression levels and a nuclear survivin localization correlated with the AA subtype, whereas cytoplasmic survivin localization correlated with the GB subtype. We also found that patients carrying tumors with a high cytoplasmic survivin expression, a high nuclear survivin expression or a high p53 expression, and who did not receive radiotherapy, exhibited poorer short-term and long-term overall survival rates. CONCLUSIONS: Our data suggest that subcellular survivin localization and p53 expression may be employed as valuable tools to improve the accuracy of the histological sub-classification of diffuse astrocytic tumors. Patients whose tumors overexpress these proteins may benefit from radiotherapy, irrespective age and/or histological classification.

Membrane microparticles: shedding new light into cancer cell communication.

BACKGROUND: Microparticles (MPs) or ectosomes are small enclosed fragments (from 0.2 to 2 µm in diameter) released from the cellular plasma membrane. Several oncogenic molecules have been identified inside MPs, including soluble proteins XIAP, survivin, metalloproteinases, CX3CL1, PYK2 and other microRNA-related proteins; membrane proteins EGFR, HER-2, integrins and efflux pumps; and messenger RNAs and microRNAs miR-21, miR-27a, let-7, miR-451, among others. Studies have shown that MPs transfer their cargo to neoplastic or non-malignant cells and thus contribute to activation of oncogenic pathways, resulting in cell survival, drug resistance and cancer dissemination. DISCUSSION AND CONCLUSION: This review summarizes recent findings on MP biogenesis and the role of the MPs cargo in cancer and discusses some of the RNAs and proteins involved. In addition, the discussion covers evidence of (1) how and which signaling pathways can be activated by MPs in recipient cells; (2) recipient cell-type selectivity in incorporation of proteins and RNAs transported by MPs; and (3) how upon stimulation, stromal cells release MPs, promoting resistance to chemotherapeutics and invasiveness in cancer cells.

Quantitative analysis of CDKN2A methylation, mRNA, and p16(INK4a) protein expression in children and adolescents with Burkitt lymphoma: biological and clinical implications.

CDKN2A is a tumor suppressor gene critical in the cell cycle regulation. Little is known regarding the role of CDKN2A methylation in the pathogenesis of Burkitt lymphoma (BL). CDKN2A methylation was investigated using pyrosequencing in 51 tumor samples. p16(INK4a) mRNA and protein levels were measured using real-time PCR and immunohistochemistry, respectively. CDKN2A methylation was detectable in 72% cases. Nuclear expression of p16(INK4a) was not detected in 41% cases. There was an association between methylation and absence of CDKN2A mRNA (P=0.003). In conclusion, CDKN2A methylation occurs at a high frequency suggesting a role in BL pathogenesis and potential therapeutic implications.

Lack of prognostic significance of survivin in pediatric medulloblastoma.

Medulloblastoma (MDB) is the most common malignant cerebellar tumor in children. Because of the significant rate of mortality and treatment-related morbidity, the identification of prognostic factors could lead to a more accurate selection of patients who can benefit from a less aggressive therapy and improve risk stratification. Survivin is an inhibitor of apoptosis protein (IAP), the expression of which has been associated with worse prognosis in MDB. However, both of its subcellular localizations may contribute to tumor progression, and ultimately, survivin subcellular localization prognostic value depends on tumor type biological features. The goal of this study was to analyze these survivin features in the pediatric MDB tumor samples and its impact on clinical outcome. Survivin expression and subcellular localization were accessed by immunohistochemistry in a series of 41 tumor samples. Kaplan-Meier survival curves were compared using the log-rank test. Survivin expression ranged from completely absent to fully present in a notably higher pattern of nuclear localization than cytoplasmic (19 of 41 versus 4 of 41, respectively). However, survivin expression and subcellular localization were not associated with five-year overall survival or metastasis status at diagnosis, which was the only statistically significant prognostic factor in our series (p = 0.008). Taken together, our results suggest that survivin expression should be further studied in large, multicenter series to determine its accurate impact on prognosis and pathobiology of pediatric MDB.