Dual action of apolipoprotein E-interacting HCCR-1 oncoprotein and its implication for breast cancer and obesity

Tumor-associated macrophages-derived exosomes promote the migration of gastric cancer cells by transfer of functional Apolipoprotein E

Tumor-associated macrophages (TAMs) are a major component of the tumor microenvironment and have been shown to contribute to tumor aggressiveness. However, the detailed mechanisms underlying the pro-metastatic effect of TAMs on gastric cancer are not clearly defined. Here, we show that TAMs are enriched in gastric cancer. TAMs are characterized by M2-polarized phenotype and promote migration of gastric cancer cells in vitro and in vivo. Furthermore, we find that M2-derived exosomes determine the TAMs-mediated pro-migratory activity. Using mass spectrometry, we identify that apolipoprotein E (ApoE) is highly specific and effective protein in M2 macrophages-derived exosomes. Moreover, TAMs are uniquely immune cells population expressed ApoE in gastric cancer microenvironment. However, exosomes derived from M2 macrophages of Apoe^−/− mice have no significant effect on the migration of gastric cancer cells in vitro and in vivo. Mechanistically, M2 macrophage-derived exosomes mediate an intercellular transfer of ApoE-activating PI3K-Akt signaling pathway in recipient gastric cancer cells to remodel the cytoskeleton-supporting migration. Collectively, our findings signify that the exosome-mediated transfer of functional ApoE protein from TAMs to the tumor cells promotes the migration of gastric cancer cells.

Association between apolipoprotein E genotype and cancer susceptibility: a meta-analysis

BACKGROUND

Apolipoprotein E (ApoE), a protein primarily involved in lipoprotein metabolism, occurs in three isoforms (E2, E3 and E4). Studies evaluating the association between APOE genotype and incidence of malignancies have given inconclusive results.

OBJECTIVE

The objective of the present study was to analyze the association between APOE genotype and incidence of cancer by a meta-analysis.

METHODS

We conducted a literature search in the electronic databases for studies with information on APOE genotype in malignancies. Sixteen studies (14 case-control and 2 cohort; 77,970 controls and 12,010 cases) were included for the present meta-analysis. Pooled odds ratios (OR) with 95 % confidence intervals (CI) were calculated assuming a random-effect model for all the genotypes and alleles. Subgroup analyses based on study design, ethnicity of populations, site of cancer and source of controls were performed as a post hoc measure. Appropriate tests to detect heterogeneity, publication bias and sensitivity were done at all stages. The review protocol is registered with the PROSPERO database vide registration number CRD42013006496.

RESULTS

The pooled effect measure for the comparisons did not reveal an association in primary analyses. In the subgroup analyses, we observed a negative association between APOE4+ genotypes and overall risk of cancer in the cohort study subgroup (pooled OR 0.86; 95 % CI 0.82-0.91; p < 0.00001; I (2) = 0 %). Sensitivity analyses did not alter the overall pooled effect measure, and there were no evidences to suggest a publication bias.

CONCLUSION

Overall, the present meta-analysis did not show any association between APOE alleles and genotypes with incidence of cancer in general.

Peroxisome proliferator activated receptor-α/hypoxia inducible factor-1α interplay sustains carbonic anhydrase IX and apoliprotein E expression in breast cancer stem cells

AIMS

Cancer stem cell biology is tightly connected to the regulation of the pro-inflammatory cytokine network. The concept of cancer stem cells "inflammatory addiction" leads to envisage the potential role of anti-inflammatory molecules as new anti-cancer targets. Here we report on the relationship between nuclear receptors activity and the modulation of the pro-inflammatory phenotype in breast cancer stem cells.

METHODS

Breast cancer stem cells were expanded as mammospheres from normal and tumor human breast tissues and from tumorigenic (MCF7) and non tumorigenic (MCF10) human breast cell lines. Mammospheres were exposed to the supernatant of breast tumor and normal mammary gland tissue fibroblasts.

RESULTS

In mammospheres exposed to the breast tumor fibroblasts supernatant, autocrine tumor necrosis factor-α signalling engenders the functional interplay between peroxisome proliferator activated receptor-α and hypoxia inducible factor-1α (PPARα/HIF1α). The two proteins promote mammospheres formation and enhance each other expression via miRNA130b/miRNA17-5p-dependent mechanism which is antagonized by PPARγ. Further, the PPARα/HIF1α interplay regulates the expression of the pro-inflammatory cytokine interleukin-6, the hypoxia survival factor carbonic anhydrase IX and the plasma lipid carrier apolipoprotein E.

CONCLUSION

Our data demonstrate the importance of exploring the role of nuclear receptors (PPARα/PPARγ) in the regulation of pro-inflammatory pathways, with the aim to thwart breast cancer stem cells functioning.

Clinical implication of elevated human cervical cancer oncogene-1 expression in esophageal squamous cell carcinoma

The human cervical cancer oncogene 1 (HCCR-1), a novel human oncoprotein, has been shown to be upregulated in various human tumors and plays a critical role in tumorigenesis and tumor progression. Here, the authors investigated HCCR-1 level in esophageal squamous cell carcinoma (ESCC) tissues and assessed the correlation between HCCR-1 level and prognosis of the patients with ESCC. HCCR-1 levels were investigated by immunohistochemistry, in situ hybridization, real-time quantitative RT-PCR and Western blotting methods; Kaplan-Meier curve was used to evaluate the prognostic value of HCCR-1 level in patients with ESCC using log-rank test. HCCR-1 displayed high levels in ESCC tissues compared to squamous dysplasia tissues and normal esophageal epithelial tissues. No significant correlation was observed between the levels of HCCR-1 mRNA and protein and gender and age (all p>0.05) but obviously related to histological grade, clinical stage, and lymph node metastasis (all p<0.001). Moreover, the survival rate of the patients with low HCCR-1 levels was higher than that of the patients with high HCCR-1 levels (both p<0.05). These data demonstrate that HCCR-1 may be used as a novel predictor for the prognosis of the patients with ESCC.

Construction of eukaryotic expression vectors expressing siRNAs targeting the HCCR2 gene and their transfection into PANC1 cells

AIM: To construct eukaryotic expression vectors expressing small interfering RNAs (siRNAs) targeting the human cervical cancer oncogene 2 (HCCR2) gene and transfect them into human pancreatic cancer cell line PANC1 to obtain a cell line stably transfected with the HCCR2 siRNA plasmid.

METHODS: Multiple siRNAs targeting the HCCR2 gene were designed, chemically synthesized, and cloned into the eukaryotic expression vector pGCsi-H1/Hygro/NEGative. The resulting recombinant vectors were identified by direct sequencing. After the recombinant pGCsi-HCCR plasmids were co-transfected with an HCCR eukaryotic expression vector into 293T cells, the protein expression of HCCR-2 was analyzed by Western blotting to identify the pGCsi-HCCR vector that had the highest gene knockdown efficiency. This recombinant vector was then transfected into PANC1 cells with LipofectamineTM 2000. G418-resistant clones were selected to obtain a stably transfected cell line. The expression of HCCR2 protein in stably transfected cell line was detected by Western blot.

RESULTS: The pGCsi-HCCR-3 plasmid had the highest gene knockdown efficiency and was used to transfect PANC1 cells. Western blotting analysis demonstrated that HCCR2 expression was significantly inhibited in PANC-1 cells stably transfected with the pGCsi-HCCR-3 plasmid compared to cells transfected with the empty vector.

CONCLUSION: Eukaryotic expression vectors expressing siRNAs targeting the HCCR2 gene were successfully constructed and a PANC-1 cell line stably transfected with the pGCsi-HCCR-3 plasmid was successfully established.