Ky Wong

Rab25 Is a Tumor Suppressor Gene with Antiangiogenic and Anti-Invasive Activities in Esophageal Squamous Cell Carcinoma

Esophageal squamous cell carcinoma (ESCC), the major histologic subtype of esophageal cancer, is a devastating disease characterized by distinctly high incidences and mortality rates. However, there remains limited understanding of molecular events leading to development and progression of the disease, which are of paramount importance to defining biomarkers for diagnosis, prognosis, and personalized treatment. By high-throughout transcriptome sequence profiling of nontumor and ESCC clinical samples, we identified a subset of significantly differentially expressed genes involved in integrin signaling. The Rab25 gene implicated in endocytic recycling of integrins was the only gene in this group significantly downregulated, and its downregulation was confirmed as a frequent event in a second larger cohort of ESCC tumor specimens by quantitative real-time PCR and immunohistochemical analyses. Reduced expression of Rab25 correlated with decreased overall survival and was also documented in ESCC cell lines compared with pooled normal tissues. Demethylation treatment and bisulfite genomic sequencing analyses revealed that downregulation of Rab25 expression in both ESCC cell lines and clinical samples was associated with promoter hypermethylation. Functional studies using lentiviral-based overexpression and suppression systems lent direct support of Rab25 to function as an important tumor suppressor with both anti-invasive and -angiogenic abilities, through a deregulated FAK-Raf-MEK1/2-ERK signaling pathway. Further characterization of Rab25 may provide a prognostic biomarker for ESCC outcome prediction and a novel therapeutic target in ESCC treatment.

DNA fingerprinting tags novel altered chromosomal regions and identifies the involvement of SOX5 in the progression of prostate cancer

Identification of genomic alterations associated with the progression of prostate cancer may facilitate the better understanding of the development of this highly variable disease. Matched normal, premalignant high‐grade prostatic intraepithelial neoplasia and invasive prostate carcinoma cells were procured by laser capture microdissection (LCM) from human radical prostatectomy specimens. From these cells, comparative DNA fingerprints were generated by a modified PCR‐based technique called scanning of microdissected archival lesion (SMAL)‐PCR. Recurrent polymorphic fingerprint fragments were used in tagging altered chromosomal regions. Altered regions were found at cytobands 1p31.3, 1q44, 2p23.1, 3p26.3, 3q22.3, 4q22.3, 4q35.2, 5q23.2, 8q22.3, 8q24.13, 9q21.3, 9q22.32, 10q11.21, 11p13, 12p12.1, 13q12.1, 16q12.2 and 18q21.31. Candidate genes in the surrounding area that may possibly harbor mutations that change normal prostatic cells to progress into their tumor stages were proposed. Of these fragments, a 420 bp alteration, absent in all 26 normal samples screened, was observed in 2 tumors. This fragment was cloned, sequenced and localized to chromosome 12p12.1. Within this region, candidate gene sex determining region Y‐box 5 (SOX5) was proposed. Further studies of SOX5 in cell lines, xenografts and human prostate specimens, at both the RNA and protein levels, found overexpression of the gene in tumors. This overexpression was then subsequently found by fluorescent in situ hybridization to be caused by amplification of the region. In conclusion, our results suggest LCM coupled with SMAL‐PCR DNA fingerprinting is a useful method for the screening and identification of chromosomal regions and genes associated with cancer development. Further, overexpression of SOX5 is associated with prostate tumor progression and early development of distant metastasis.

KIF7 attenuates prostate tumor growth through LKB1-mediated AKT inhibition

This study investigated kinesin family member 7 (KIF7) expression and function in prostate cancer (PCa). Our results showed that KIF7 was significantly downregulated in PCa, compared with normal, benign prostatic hyperplasia and prostate intraepithelial neoplasia tissues, partially through promoter hypermethylation. We further investigated the effects of KIF7 coiled coil (CC) domain and motor domain (MD) on PCa development in vitro and in vivo. Our results showed that KIF7-CC but not KIF7-MD significantly attenuated proliferation and colony formation, impeded migration and invasion, induced apoptosis and sensitized PCa cells to paclitaxel. Further analysis revealed that KIF7-CC enhanced LKB1 expression and phosphorylation at Ser428, which induced PTEN phosphorylation at Ser380/Thr382/383 and consequently blocked AKT phosphorylation at Ser473. Downregulation of LKB1 significantly attenuated the suppressive effects of KIF7-CC on cell proliferation, colony formation and AKT phosphorylation. Furthermore, our in vivo studies showed that KIF7-CC reduced prostate tumorigenesis in cell-derived xenografts. Downregulation of LKB1 abrogated the anti-tumor effects of KIF7-CC in these xenografts. Taken together, these findings provide the first evidence to support the role of KIF7 as a negative regulator that inhibits PCa development partially through LKB1-mediated AKT inhibition.This study investigated kinesin family member 7 (KIF7) expression and function in prostate cancer (PCa). Our results showed that KIF7 was significantly downregulated in PCa, compared with normal, benign prostatic hyperplasia and prostate intraepithelial neoplasia tissues, partially through promoter hypermethylation. We further investigated the effects of KIF7 coiled coil (CC) domain and motor domain (MD) on PCa development in vitro and in vivo. Our results showed that KIF7-CC but not KIF7-MD significantly attenuated proliferation and colony formation, impeded migration and invasion, induced apoptosis and sensitized PCa cells to paclitaxel. Further analysis revealed that KIF7-CC enhanced LKB1 expression and phosphorylation at Ser428, which induced PTEN phosphorylation at Ser380/Thr382/383 and consequently blocked AKT phosphorylation at Ser473. Downregulation of LKB1 significantly attenuated the suppressive effects of KIF7-CC on cell proliferation, colony formation and AKT phosphorylation. Furthermore, our in vivo studies showed that KIF7-CC reduced prostate tumorigenesis in cell-derived xenografts. Downregulation of LKB1 abrogated the anti-tumor effects of KIF7-CC in these xenografts. Taken together, these findings provide the first evidence to support the role of KIF7 as a negative regulator that inhibits PCa development partially through LKB1-mediated AKT inhibition.

Abstract 1548: Down-regulation of 4-hydroxyphenylpyruvate dioxygenate (HPD) contributes to the pathogenesis of hepatocellular carcinoma (HCC) through ERK / BCL-2 signalling activation

Hepatocellular carcinoma (HCC) is one of the most prevalent malignancies in the world. Metastasis, recurrence and therapy resistance remain major obstacles to the improvement of long-term survival and represent major causative factors contributing to the rising mortality rates and poor prognosis of HCC. Identification of key drivers important for clinical prognostic utility and elucidation of mechanisms involved in hepatocarcinogenesis is urgently needed to aid in the development of novel treatment modalities. To this end, we began our study with an analysis of a publicly gene expression dataset (GSE14520) comprising of transcriptomic profiles from a large cohort of human non-tumor liver and HCC clinical samples in hope to establish a prognostic gene signature associated with metastatic risk / recurrence status so to identify novel driver genes responsible for HCC development and progression. By this method, 4-hydroxyphenylpyruvate dioxygenase (HPD) was identified as a candidate tumor suppressor gene in HCC. HPD was found to be frequently down-regulated in primary HCC tumors as compared with peri-tumor liver tissues. Its expression negatively correlated with aggressive HCC pathological features, including tumor stage, metastasis, recurrence and survival. Notably, down-regulated HPD expression in HCC is in part a result of hypermethylation at the HPD promoter. The functional effect of HPD was then examined in HCC cells with or without HPD stably repressed or ectopically overexpressed. Upon knockdown of HPD, HCC cells displayed significantly enhanced abilities to form tumors, metastasize and confer sorafenib resistance in vitro and in vivo. Conversely, overexpression of HPD in HCC cells led to an opposing effect. Consistently, sorafenib-resistant HCC patient derived xenografts also displayed attenuated levels of HPD as compared with parental sorafenib-sensitive counterparts. Mechanistically, HPD down-regulation mediates aggressive cancer features in HCC through activation of an ERK and BCL-2 pro-survival signaling pathway, as evidenced by rescue experiments involving the ERK inhibitor U0126. Collectively, our findings suggest HPD down-regulation in HCC tumors to promote tumorigenicity, metastasis and sorafenib resistance through ERK / BCL-2 signaling activation and that HPD may represent a novel prognostic biomarker for HCC. Citation Format: Man Tong, Tin Lok Wong, Steve Tin-Chi Luk, Noelia Che, Kai Yau Wong, Tsun Ming Fung, Xin-Yuan Guan, Nikki P Lee, Yun-Fei Yuan, Terence K Lee, Stephanie Ma. Down-regulation of 4-hydroxyphenylpyruvate dioxygenate (HPD) contributes to the pathogenesis of hepatocellular carcinoma (HCC) through ERK / BCL-2 signalling activation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1548. doi:10.1158/1538-7445.AM2017-1548