Je-Ho Lee

Insulin-like growth factor-binding protein 5 (IGFBP-5) plays a role in cell growth, differentiation, and apoptosis. In this study, we found that IGFBP5 was markedly downregulated in ovarian cancer tissue. We investigated the functional significance of IGFBP-5 as a tumor suppressor. To determine functional regions of IGFBP-5, truncation mutants were prepared and were studied the effect on tumor growth. Expression of C-terminal region of IGFBP-5 significantly decreased tumor growth in an ovarian cancer xenograft. A peptide derived from the C-terminus of IGFBP-5 (BP5-C) was synthesized to evaluate the minimal amino acid motif that retained anti-tumorigenic activity and its effect on angiogenesis was studied. BP5-C peptide decreased the expression of VEGF-A and MMP-9, phosphorylation of Akt and ERK, and NF-kB activity, and inhibited angiogenesis in in vitro and ex vivo systems. Furthermore, BP5-C peptide significantly decreased tumor weight and angiogenesis in both ovarian cancer orthotopic xenograft and patient-derived xenograft mice. These results suggest that the C-terminus of IGFBP-5 exerts anti-cancer activity by inhibiting angiogenesis via regulation of the Akt/ERK and NF-kB–VEGF/MMP-9 signaling pathway, and might be considered as a novel angiogenesis inhibitor for the treatment of ovarian cancer.

The p53 tumor suppressor function can be compromised in many tumors by the cellular antagonist HDM2 and human papillomavirus oncogene E6 that induce p53 degradation. Restoration of p53 activity has strong therapeutic potential. Here, we identified TSC-22 as a novel p53-interacting protein and show its novel function as a positive regulator of p53. We found that TSC-22 level was significantly down-regulated in cervical cancer tissues. Moreover, over-expression of TSC-22 was sufficient to inhibit cell proliferation, promote cellular apoptosis in cervical cancer cells and suppress growth of xenograft tumors in mice. Expression of also TSC-22 enhanced the protein level of p53 by protecting it from poly-ubiquitination. When bound to the motif between amino acids 100 and 200 of p53, TSC-22 inhibited the HDM2- and E6-mediated p53 poly-ubiquitination and degradation. Consequently, ectopic over-expression of TSC-22 activated the function of p53, followed by increased expression of p21^Waf1/Cip1 and PUMA in human cervical cancer cell lines. Interestingly, TSC-22 did not affect the interaction between p53 and HDM2. Knock-down of TSC-22 by small interfering RNA clearly enhanced the poly-ubiquitination of p53, leading to the degradation of p53. These results suggest that TSC-22 acts as a tumor suppressor by safeguarding p53 from poly-ubiquitination mediated-degradation.

Ovarian cancer is a gynecological cancer with a high death rate. We utilized global gene expression profiles of ovarian carcinomas obtained by complementary DNA (cDNA) microarray to identify ovarian cancer-specific proteins. CD9 was upregulated in ovarian carcinomas, and overexpression of the CD9 protein was detected in ovarian carcinomas by immunohistochemistry. CD9 was also overexpressed in several cancer cell lines, including ovarian cancer cells. In order to elucidate the biological significance of highly expressed CD9 in cancer cells, functional studies of CD9 were performed by ectopic expression, knockdown of CD9 using small interfering RNA (siRNA) and blockage of CD9 activity using the CD9-specific monoclonal antibody ALB6. Ectopic CD9 induced cell survival. In order to identify signaling pathways related to CD9, the gene expressions of CD9/SKOV3 cells were analyzed by cDNA microarray. Among the many upregulated genes, tumor necrosis factor (TNF)- α was induced in CD9/SKOV3 cells. The effect of overexpressed CD9 on the downstream signaling events of TNF-α was further investigated. In CD9/SKOV3 cells, the nuclear factor-kappaB (NF-κB)-signaling pathway was constitutively activated. Knockdown of CD9 by siRNA and blockage of CD9 activity by ALB6 in ovarian cancer cells demonstrated that constitutive activation of NF-κB is CD9 dependent and that CD9 is involved in anti-apoptosis. A CD9 functional study was performed in an ovarian cancer-xenograft mouse by injecting ALB6 into the peritoneum. ALB6 resulted in reduced tumor weight compared with that of control IgG ₁ . Collectively, these results demonstrate that CD9 functions as an oncogene and represents a target for the development of cancer-specific therapeutics.

A 52‐year‐old woman had undergone a partial cystectomy for a cystic mass at the dome of the urinary bladder in 1997. The pathological diagnosis was a urachal mucinous cystadenoma with borderline malignancy. Twelve years later, multiple masses were noted on the uterus, ovaries and abdominal wall. She underwent debulking surgery, including a total hysterectomy, bilateral salpingo‐oophorectomy, pelvic lymph node dissection, infracolic omentectomy, appendectomy, colon mass removal and abdominal wall mass removal. Remnants of the tumor were seeded throughout the abdominal cavity. The pathological evaluation confirmed metastatic urachal mucinous adenocarcinoma in both ovaries, the abdominal wall, the colon mass, the uterosacral ligament and the bladder. Adjuvant chemotherapy with paclitaxel and carboplatin was administered, which showed stable disease. She is now undergoing second‐line chemotherapy.

Experimental & Molecular Medicine is an open access journal that publishes the highest quality articles in translational research and biomedical studies.

Using the DDRT‐PCR, a series of differentially expressed genes in human primary cervical cancer was isolated. Among the 250 PCR amplimers, 88 gene fragments were confirmed by reverse Northern hybridization. Homology searches indicated that 26 out of 88 were previously known genes including calmodulin, human BBC1, histone H3.3, a series of ribosomal proteins (RPL19, RPS19, and RPS12), translation initiation factor (elF‐4AI), lactoferrin, integrin a6, cell‐surface antigens (CD9 and CD59), transcription factor (mbp‐1), and mitochondrial proteins. Several unknown clones showed sequence homology with known genes. Furthermore, six of the unknown genes showed identical sequence with expressed sequence tags (EST) of unknown function. Differential expression patterns of identified genes were further examined and confirmed with multiple pairs of cervical cancer samples using Northern hybridization. Our profiling of differentially expressed genes may provide useful information about the underlying genetic alterations in human cervical carcinoma and diagnostic markers for this disease. The precise roles of these genes in cancer development remain to be elucidated

The Wnt/β‐catenin signaling pathway is activated during the malignant transformation of keratinocytes that originate from the human uterine cervix. Dkk1, 2 and 4 have been shown to modulate the Wnt‐induced stabilization of the β‐catenin signaling pathway. However, the function of Dkk3 in this pathway is unknown. Comparison of the Dkk3 gene expression profiles in cervical cancer and normal cervical tissue by cDNA microarray and subsequent real‐time PCR revealed that the Dkk3 gene is frequently downregulated in the cancer. Methylation studies showed that the promoter of Dkk3 was methylated in cervical cancer cell lines and 22 (31.4%) of 70 cervical cancer tissue specimens. This promoter methylation was associated with reduced expression of Dkk3 mRNA in the paired normal and tumor tissue samples. Further, the reintroduction of Dkk3 into HeLa cervical cancer cells resulted in reduced colony formation and retarded cell growth. The forced expression of Dkk3 markedly attenuated β‐catenin‐responsive luciferase activity in a dose‐dependent manner and decreased the β‐catenin levels. By utilizing a yeast two‐hybrid screen, βTrCP, a negative regulator of β‐catenin was identified as a novel Dkk3‐interacting partner. Coexpression with βTrCP synergistically enhanced the inhibitory function of Dkk3 on β‐catenin. The stable expression of Dkk3 blocks the nuclear translocation of β‐catenin, resulting in downregulation of its downstream targets (VEGF and cylcin D), whereas knockdown of Dkk3 abrogates this blocking. We conclude from our finding that Dkk3 is a negative regulator of β‐catenin and its downregulation contribute to an activation of the β‐catenin signaling pathway.

The tissue inhibitors of metalloproteinases (TIMPs) are complex molecules with both pro- and anti-tumour effects. Thus, their diverse expression could be because of their multifunctional properties with respect to tumour growth, angiogenesis, apoptosis, and other biological functions. Previous data have shown that TIMPs bind tightly to most matrix metalloproteinases, although the pathway that mediates angiostatic activity has not been fully established. As an initial step to elucidate the mechanism that regulates TIMP-3, we used a yeast two-hybrid system to screen a human ovary cDNA library for a novel TIMP-3-interacting partner. Here, we identified human angiotensin II type 2 receptor (AGTR2) as such a partner, which is well known to be a regulator of cardiovascular homoeostasis. In this present study, we investigated whether AGTR2-mediated apoptotic activity can inhibit the growth of ovarian cancer in an experimental model system. AGTR2 treatment was found to be more effective in inhibiting ovarian cancer growth than the treatment with TIMP-3 in parallel experiments. Subsequently, the efficacy of the combined treatment with TIMP-3 and AGTR2 was investigated. In the presence of both of these proteins, vascular endothelial growth factor-induced human umbilical vein endothelial cell proliferation was additively inhibited, and the inhibition of Akt and endothelial NO synthase phosphorylation was blocked. These combined results suggest that two angiostatic molecules may have an important biological role in regulating potent anti-angiogenic effects and possibly may have a role in anti-tumour therapy.

SUMOylation of transcription factors often attenuates transcription activity. This regulation of protein activity allows more diversity in the control of gene expression. Interferon regulatory factor-1 (IRF-1) was originally identified as a regulator of IFN-α/β, and its expression is induced by viral infection or IFN stimulation. Accumulating evidence supports the theory that IRF-1 functions as a tumor suppressor and represses the transformed phenotype. Here we report that the level of SUMOylated IRF-1 is elevated in tumors. Site-directed mutagenesis experiments disclose that the SUMOylation sites of IRF-1 are identical to the major ubiquitination sites. Consequently, SUMOylated IRF-1 displays enhanced resistance to degradation. SUMOylation of IRF-1 attenuates its transcription activity, and SUMOylated IRF-1 inhibits apoptosis by repression of its transcriptional activity. These data support a mechanism whereby SUMOylation of IRF-1 inactivates its tumor suppressor function, which facilitates resistance to the immune response.