Yamashita 24-10

HOX genes encode transcription factors that function to establish basic body pattern during embryogenesis and maintain the function of specific organs in the adult. Recent studies have demonstrated that HOX genes are also involved in oncogenesis in a range of malignancies. To elucidate whether HOX genes contribute to ovarian carcinogenesis, we created an expression profile of HOX genes using ovarian derived materials from surgical samples and epithelial ovarian cancer cells derived from five different cell lines. Real-time quantitative RT-PCR assay indicated overexpression of 14 HOX genes in clusters A and B but only 2 genes in clusters C and D. Of the 16 HOX genes, overexpression of paralogs of HOX3, HOX4 and HOX7 is seen in cluster A and B, and of HOX13 in all paralogs. In addition, HOXB7, HOXA13 and HOXB13 showed high levels of overexpression in cancer cells and tissues whereas no or little expression was observed in normal controls. To examine whether overexpressed HOX genes regulate invasion of ovarian cancer cells directly, we introduced an antisense DNA fragment of overexpressed HOXB7 and HOXB13, and HOXC5 that did not show overexpression into SKOV3 cells by electroporation. Antisense introduction followed by chemoinvasion assay using matrigel chamber demonstrated that SKOV3 cells introduced an antisense of each HOXB7 and HOXB13 showed 85% and 50% reduction of invasion ability compared to the parental SKOV3 cells, respectively. In contrast, antisense of HOXC5 introduced cells showed no significant difference of the invasion ability. These results suggest an important role of overexpressed HOX genes, especially for invasive characteristics of ovarian cancer cells. Introduction Epithelial ovarian cancer is a significant female disease with a high rate of mortality, mainly because most patients are diagnosed at advanced clinical stages due to their delay in visiting a hospital and the easy diffusion of cancer cells into pelvic and abdominal cavities (1). Thus, elucidating the mechanisms of invasion and metastasis in ovarian cancer is essential for understanding the nature of ovarian cancer. In order to invade or metastasize, the cancer cells must move from the ovarian surface lesion, inside or outside of the ovary as a primary site, to secondary metastatic sites. This involves detachment from neighboring cells, transfer of the cells after intravasation, and then proliferation after extravasation. This complicated functional alteration of the cells requires changes in the characteristics of the cells, such as the phenomenon seen in epithelial mesenchymal transition (EMT) regulated by several molecules such as TGF, Ras, Wnt and Snail (2-10). In early embryogenesis, these molecules are also utilized to form the basic embryonic body pattern via EMT. HOX genes, encoding homeodomain as DNA-binding domain and consisting of 39 members in four different clusters, are one type of such regulatory transcription molecules that express in the anterior-posterior axis, limbs, and genital buds during mammalian embryogenesis. Published studies suggest that HOX genes provide intercellular information for the determination of identity, lineage and fate of the cells (11,12). Interestingly, recent reports have provided evidence that the abnormal expression of certain HOX genes is observed in a variety of malignancies such as hematologic, breast, colon, prostate, bladder, lung, and thyroid cancer (13-22). In the gynecologic field, there are several reports describing that abnormal expression of particular HOX genes seems to be involved in cervical, ovarian and endometrial neoplasms (23-26) including a recent report by Zhao et al (27). In the context of embryonic development, the expression of invasive characteristics of cancer cells might be a similar phenomenon, analogous to the movement of normal embryonic cells mediated by expression of HOX genes. This leads to a possibility that overexpression of certain HOX genes in ovarian cancer cells could accelerate invasion of the cancer cells. In this study, we first created an expression profile of HOX genes in ovarian-derived samples to investigate whether INTERNATIONAL JOURNAL OF ONCOLOGY 28: 931-938, 2006 931 Suppression of invasive characteristics by antisense introduction of overexpressed HOX genes in ovarian cancer cells TSUYOSHI YAMASHITA, SEISHIRO TAZAWA, ZHAO YAWEI, HIDETO KATAYAMA, YASUHITO KATO, KUNIHIKO NISHIWAKI, YUKO YOKOHAMA and MUTSUO ISHIKAWA Department of Obstetrics and Gynecology, Asahikawa Medical College, Midorigaoka, Higashi 2-1-1-1, Asahikawa 078-8510, Japan Received October 24, 2005; Accepted December 12, 2005 _________________________________________ Correspondence to: Dr Tsuyoshi Yamashita, Department of Obstetrics and Gynecology, Asahikawa Medical College, Midorigaoka, Higashi 2-1-1-1, Asahikawa 078-8510, Japan E-mail: [email protected]