Immunoregulatory Protein B7-H3 Reprograms Glucose Metabolism in Cancer Cells by ROS-Mediated Stabilization of HIF1α.

B7-H3 is a member of B7 family of immunoregulatory transmembrane glycoproteins expressed by T cells. While B7-H3 overexpression is associated with poor outcomes in multiple cancers, it also has immune-independent roles outside T cells and its precise mechanistic contributions to cancer are unclear. In this study, we investigated the role of B7-H3 in metabolic reprogramming of cancer cells in vitro and in vivo We found that B7-H3 promoted the Warburg effect, evidenced by increased glucose uptake and lactate production in B7-H3-expressing cells. B7-H3 also increased the protein levels of HIF1α and its downstream targets, LDHA and PDK1, key enzymes in the glycolytic pathway. Furthermore, B7-H3 promoted reactive oxygen species-dependent stabilization of HIF1α by suppressing the activity of the stress-activated transcription factor Nrf2 and its target genes, including the antioxidants SOD1, SOD2, and PRX3. Metabolic imaging of human breast cancer xenografts in mice confirmed that B7-H3 enhanced tumor glucose uptake and tumor growth. Together, our results illuminate the critical immune-independent contributions of B7-H3 to cancer metabolism, presenting a radically new perspective on B7 family immunoregulatory proteins in malignant progression. Cancer Res; 76(8); 2231-42. ©2016 AACR.

Knockout of BRD7 results in impaired spermatogenesis and male infertility.

BRD7 was originally identified as a novel bromodomain gene and a potential transcriptional factor. BRD7 was found to be extensively expressed in multiple mouse tissues but was highly expressed in the testis. Furthermore, BRD7 was located in germ cells during multiple stages of spermatogenesis, ranging from the pachytene to the round spermatid stage. Homozygous knockout of BRD7 (BRD7(-/-)) resulted in complete male infertility and spermatogenesis defects, including deformed acrosomal formation, degenerative elongating spermatids and irregular head morphology in postmeiotic germ cells in the seminiferous epithelium, which led to the complete arrest of spermatogenesis at step 13. Moreover, a high ratio of apoptosis was determined by TUNEL analysis, which was supported by high levels of the apoptosis markers annexin V and p53 in knockout testes. Increased expression of the DNA damage maker λH2AX was also found in BRD7(-/-) mice, whereas DNA damage repair genes were down-regulated. Furthermore, no or lower expression of BRD7 was detected in the testes of azoospermia patients exhibiting spermatogenesis arrest than that in control group. These data demonstrate that BRD7 is involved in male infertility and spermatogenesis in mice, and BRD7 defect might be associated with the occurrence and development of human azoospermia.

Multifaceted roles of HSF1 in cancer.

Heat shock transcription factor 1 (HSF1) is the master regulator of the heat shock response. Accumulating evidence shows that HSF1 is overexpressed in a variety of human cancers, is associated with cancer aggressiveness, and could serve as an independent diagnostic or prognostic biomarker. In this review, we will provide an overview of the multifaceted roles of HSF1 in cancer, with a special focus on the four underlying molecular mechanisms involved. First, HSF1 regulates the expression of heat shock proteins (HSPs) including HSP90, HSP70, and HSP27. Second, HSF1 regulates cellular metabolism, including glycolysis and lipid metabolism. Third, HSF1 serves as a regulator of different signaling pathways, such as HuR-HIF-1, Slug, protein kinase C (PKC), nuclear factor-kappaB (NF-κB), PI3K-AKT-mTOR, and mitogen-activated protein kinase (MAPK) pathways. Finally, HSF1 regulates microRNAs (miRNAs) and long non-coding RNAs (lncRNAs). Overall, HSF1 plays many important roles in cancer via regulating cell proliferation, anti-apoptosis, epithelial-mesenchymal transition (EMT), migration, invasion, and metastasis and may be a potential therapeutic target for human cancers.

SPLUNC1 is associated with nasopharyngeal carcinoma prognosis and plays an important role in all-trans-retinoic acid-induced growth inhibition and differentiation in nasopharyngeal cancer cells.

Human SPLUNC1 can suppress nasopharyngeal carcinoma (NPC) tumor formation; however, the correlation between SPLUNC1expression and NPC patient prognosis has not been reported. In the present study, we used a large-scale sample of 1015 tissue cores to detect SPLUNC1 expression and its association with patient prognosis. SPLUNC1 expression was reduced in NPC samples compared to nontumor nasopharyngeal epithelium tissues. Positive expression of SPLUNC1 in NPC predicted a better prognosis (disease-free survival, P = 0.034; overall survival, P = 0.048). Cox's proportional hazards model revealed that SPLUNC1 could be a significant prognostic factor affecting disease-free survival (P = 0.027). A cDNA micro-array analyzed by significant analysis of micro-array (SAM) and ingenuity pathway analysis (IPA) revealed that an indirect interaction existed between SPLUNC1 and retinoic acid (RA) in the cancer regulatory network. To further investigate the molecular mechanisms involved, we utilized several bioinformatics tools and identified 12 retinoid X receptors heterodimer binding sites in the promoter region of the SPLUNC1 gene. The transcriptional activity of the SPLUNC1 promoter was up-regulated significantly by all-trans-retinoic acid (ATRA). SPLUNC1 and retinoic acid receptor expression were induced significantly by ATRA, and removal of ATRA led to a progressive loss of SPLUNC1 and retinoic acid receptor expression. ATRA inhibited proliferation and induced the differentiation of NPC cells. Interestingly, over-expression of SPLUNC1 sensitized NPC cells to ATRA, whereas knockdown of SPLUNC1 in HNE1 cells increased cell viability. Under SPLUNC1 knockdown conditions, differentiation was reversed by ATRA treatment. We concluded that SPLUNC1 could potentially predict prognosis for NPC patients and play an important role in ATRA-induced growth inhibition and differentiation in NPC cells.

Identification of candidate biomarkers for the early detection of nasopharyngeal carcinoma by quantitative proteomic analysis.

Nasopharyngeal carcinoma (NPC) is a major head and neck cancer with high occurrence in Southeast Asia and southern China. To identify novel biomarkers for the early detection of NPC patients, 2D-DIGE combined with MALDI-TOF-MS analysis was performed to identify differentially expressed proteins in the carcinogenesis and progression of NPC using LCM-purified normal nasopharyngeal epithelial tissues and various stages of NPC biopsies. As a result, 26 differentially expressed proteins were identified, of which two proteins with sharp expressional changes in the carcinogenic process, ENO1 and CYPA, were validated by western blot analysis and identified as critical seed proteins in the functional network. Immunohistochemistry assay was further performed to detect the expression of the two proteins with a tissue microarray that included various stages of NPC tissues. The ability of these proteins to detect NPC early was evaluated via a receiver operating characteristic analysis. The results indicated that the combination of the two proteins could perfectly discriminate NNET and AH from stage I of NPC with high sensitivity and specificity, which is more effective than using either of the two proteins individually. In summary, the combination of ENO1 and CYPA can serve as potential molecular markers for the early detection of NPC. BIOLOGICAL SIGNIFICANCE: NPC is a lethal malignancy that is most prevalent in Southeast Asia, and early detection and treatment are essential for the survival and good prognosis of NPC patients. In the present work, we identified 26 differentially expressed proteins in NNET, AH and different stages of NPC tissues by using 2D-DIGE combined with MALDI-TOF/TOF analysis. Of these proteins, the down-regulation of ENO1 and over-expression of CYPA were confirmed with a high-throughput tissue microarray that included various stages of NPC tissues via an IHC assay, and the results indicated that the combination of ENO1 and CYPA can serve as a potential molecular marker for the early detection of NPC.

miR-125b functions as a key mediator for snail-induced stem cell propagation and chemoresistance.

Chemoresistance is a major obstacle in cancer treatment. Our previous studies have shown that miR-125b plays an important role in chemoresistance. Here we report a novel mechanism that up-regulation of miR-125b through Wnt signaling by Snail enriches cancer stem cells. Overexpression of Snail dramatically increases the expression of miR-125b through the Snail-activated Wnt/ß-catenin/TCF4 axis. Snail confers chemoresistance by repressing Bak1 through up-regulation of miR-125b. Restoring the expression of Bak1 or depleting miR-125b re-sensitizes Snail-expressing cancer cells to Taxol, indicating that miR-125b is critical in Snail-induced chemoresistance. Moreover, overexpression of miR-125b significantly increases the cancer stem cell population (CD24-CD44+), while depletion of miR-125b or rescue of the expression of Bak1 increases the non-stem cell population (CD24+CD44+) in Snail-overexpressing cells. These findings strongly support that miR-125b functions as a key mediator in Snail-induced cancer stem cell enrichment and chemoresistance. This novel mechanism for Snail-induced stem cell propagation and chemoresistance may have important implications in the development of strategies for overcoming cancer cell resistance to chemotherapy.