HOX genes are transcription factors that play important roles in body patterning and many cellular processes during embryonic, fetal, and adult development. Given their important function in normal tissues, it is reasonable to assume that abnormal expression of HOX genes in adults could lead to serious diseases such as cancer. Our previous study reported HOXB5 to be significantly up-regulated in breast cancer, and its expression was found to be associated with tumor cell proliferation and invasion. Furthermore, the epidermal growth factor receptor (EGFR), a cellular tyrosine kinase that plays an important role in breast cancer progression, was found significantly up-regulated by HOXB5 in ER-positive breast cancer cells. In the present study, we demonstrated that HOXB5 regulates EGFR expression at the transcriptional level by directly binding to its promoter region and promotes phosphorylation of EGFR as well as its downstream effectors. Patients with ER-positive breast cancer, having high co-expression of HOXB5 and EGFR, had poor prognosis than those with low expression. Knockdown studies validated a key role played by EGFR in the HOXB5-induced invasion of breast cancer cells. These results suggest that targeting EGFR could be an effective strategy to treat breast cancer in patients with high HOXB5 expression.

HOX genes encode a family of transcriptional regulators that are involved in pattern formation and organogenesis during embryo development. In addition, these genes play important roles in adult tissues and some of the dysregulated HOX genes are associated with cancer development and metastasis. Like many other HOX genes, HOXC9 is aberrantly expressed in certain breast cancer cell lines and tissues; however, its specific functions in breast cancer progression were not investigated. In the present study, we demonstrated that HOXC9 overexpression in breast cancer cell lines such as MDA-MB-231 and MCF7 increased the invasiveness but reduced the proliferation of cells, resembling a phenotype switch from a proliferative to an invasive state. Furthermore, the reciprocal result was detected in MCF7 and BT474 cells when the expression level of HOXC9 was reduced with siRNA. The clinical impact of HOXC9 in breast cancer was interpreted from the survival analysis data, in which high HOXC9 expression led to considerably poorer disease-free survival and distant metastasis-free survival, especially in lymph node-positive patients. Together, the prognostic relevance of HOXC9 and the HOXC9-derived phenotypic switch between proliferative and invasive states in the breast cancer cell lines suggest that HOXC9 could be a prognostic marker in breast cancer patients with lymph node metastasis and a target for therapeutic intervention in malignant breast cancer.

Mast cells are an effector cell that plays a pivotal role in type I hypersensitive immune responses. Mast cells exist in connective tissues, such as skin and mucosal tissue, and contain granules which contain bioactive substances such as histamine and heparin in cells. The granules of mast cells are secreted by antigen stimulation to cause the type I allergic hypersensitivity. In addition, stimulated by antigen, mast cells synthesize and secrete various eicosanoids and cytokines. While AT9283 is known to have anticancer effects, the therapeutic effect of AT9283 on allergic disorders is completely unknown. In this study, it was found that AT9283 reversibly inhibited antigen-IgE binding-induced degranulation in mast cells (IC 50 , approx. 0.58 μM) and suppressed the secretion of the inflammatory cytokines IL-4 (IC 50 , approx. 0.09 μM) and TNF-α (IC 50 , approx. 0.19 μM). For a mechanism of mast cell inhibition, while not inhibiting Syk phosphorylation, AT9283 suppressed the activation of LAT, a downstream substrate protein of Syk, in a dose-dependent manner. As expected, AT9283 also inhibited the activation of PLCγ1 and Akt, downstream signaling molecules of Syk/LAT, and MAP kinases such as JNK, Erk1/2, and P38. In an in vitro protein tyrosine kinase assay, AT9283 directly inhibited Syk activity. Next, AT9283 dose-dependently inhibited passive cutaneous anaphylaxis (PCA), an IgE-mediated allergic acute response, in mice (ED50, approx. 34 mg/kg, p.o.). These findings suggest that AT9283 has potential to use as a new drug for alleviating the symptoms of IgE-mediated allergic disorders.

Hox genes are responsible for encoding transcription factors that are essential for anterior-posterior body patterning at early stages of embryogenesis. However, detailed mechanisms of Hox genes are yet to be defined. Protein kinase B alpha (Akt1) was previously identified as a possible upstream regulator of Hox genes. Furthermore, the Hoxc11 gene has been upregulated in Akt1 null (Akt1-/-) mouse embryonic fibroblasts (MEFs), while repressed in wild-type MEFs. In this study, we propose to investigate the role of Gcn5, a histone acetyltransferase, in the regulation of Hoxc11 expression in MEFs. We showed that the H3 lysine 9 acetylation (H3K9ac) status has the same correlation with Hoxc11 expression and reported that Gcn5 is associated with the upregulation of Hoxc11 expression through H3K9ac in Akt1-/- MEFs. Since Hoxc11 was upregulated through histone acetylation in Akt1-/- MEFs, a functional role of Gcn5 on Hoxc11 expression was analyzed in Akt1-/- MEFs treated with Gcn5 specific inhibitor or transfected with Gcn5-small interfering RNA (Gcn5-siRNA). When the expression of Hoxc11 was analyzed using RT-PCR and real-time PCR, the Hoxc11 mRNA level was found to be similar in both Akt1-/- MEFs and control-siRNA transfected Akt1-/- MEFs. However, the Hoxc11 expression level was decreased in Gcn5-inhibited or Gcn5-knockdown Akt1-/- MEFs. Additionally, to analyze Gcn5-mediated histone acetylation status, chromatin immunoprecipitation assay was carried out in Gcn5-siRNA-transfected Akt1-/- MEFs. The H3K9ac at the Hoxc11 locus was decreased in Gcn5-knockdown Akt1-/- MEFs compared to controls. Based on these findings, we conclude that Gcn5 regulates Hoxc11 gene expression through mediating site-specific H3K9 acetylation in Akt1-/- MEFs.

HOX genes are transcription factors that play important roles in body patterning and cell fate specification during normal development. In previous study, we found aberrant overexpression of HOXB5 in breast cancer tissues and cell lines, and demonstrated that HOXB5 is important in regulation of cell proliferation, tamoxifen resistance, and invasiveness through the epithelial-mesenchymal transition (EMT). Although the relationship between HOXB5 and phenotypic changes in MCF7 breast cancer cells has been studied, the molecular function of HOXB5 as a transcription factor remains unclear. IL-6 has been reported to be involved in not only inflammation but also cancer progression, which is characterized by the increase of growth speed and invasiveness of tumor cells. In this study, we selected Interleukin-6 (IL-6) as HOXB5 putative downstream target gene and discovered that HOXB5 transcriptionally up-regulated the expression of IL-6 in HOXB5 overexpressing MCF7 cells. The upstream region (~1.2 kb) of IL-6 promoter turned out to contain several putative HOX consensus binding sites. Chromatin immunoprecipitation assay confirmed that HOXB5 directly binds to the promoter region of IL-6 and positively regulated the expression of IL-6. These data all together, indicate that HOXB5 promotes IL-6 transcription by actively binding to the putative binding sites located in the upstream region of IL-6, which enable to increase its promoter activity in MCF7 breast cancer cells.