Ka Yin Kwong

Bio: Ka Yin Kwong is an academic researcher from University of Texas MD Anderson Cancer Center. The author has contributed to research in topics: Cell growth & Genetic enhancement. The author has an hindex of 8, co-authored 8 publications receiving 2171 citations.

Nuclear localization of EGF receptor and its potential new role as a transcription factor

Abstract: Epidermal growth factor receptor (EGFR) has been detected in the nucleus in many tissues and cell lines. However, the potential functions of nuclear EGFR have largely been overlooked. Here we demonstrate that nuclear EGFR is strongly correlated with highly proliferating activities of tissues. When EGFR was fused to the GAL4 DNA-binding domain, we found that the carboxy terminus of EGFR contained a strong transactivation domain. Moreover, the receptor complex bound and activated AT-rich consensus-sequence-dependent transcription, including the consensus site in cyclin D1 promoter. By using chromatin immunoprecipitation assays, we further demonstrated that nuclear EGFR associated with promoter region of cyclin D1 in vivo. EGFR might therefore function as a transcription factor to activate genes required for highly proliferating activities.

β-Catenin, a novel prognostic marker for breast cancer: Its roles in cyclin D1 expression and cancer progression

Abstract: β-Catenin can function as an oncogene when it is translocated to the nucleus, binds to T cell factor or lymphoid enhancer factor family members, and transactivates its target genes. In this study, we demonstrate that cyclin D1 is one of the targets of β-catenin in breast cancer cells. Transactivation of β-catenin correlated significantly with cyclin D1 expression both in eight breast cell lines in vitro and in 123 patient samples. More importantly, we found that high β-catenin activity significantly correlated with poor prognosis of the patients and was a strong and independent prognostic factor in breast cancer. Our studies, therefore, indicated that β-catenin can be involved in breast cancer formation and/or progression and may serve as a target for breast cancer therapy.

The Ets protein PEA3 suppresses HER-2/neu overexpression and inhibits tumorigenesis

Abstract: Because HER-2/neu overexpression is important in cancer development, we looked for a method of suppressing the cell transformation mediated by HER-2/neu overexpression. We have identified that the DNA-binding protein PEA3, which is encoded by a previously isolated gene of the ets family, specifically targeted a DNA sequence on the HER-2/neu promoter and downregulated the promoter activity. Expression of PEA3 resulted in preferential inhibition of cell growth and tumor development of HER-2/neu-overexpressing cancer cells. This is a new approach to targeting HER-2/neu overexpression and also provides a rationale to the design for repressors of diseases caused by overexpression of pathogenic genes.

A novel splice variant of her2 with increased transformation activity

Abstract: The HER2 proto-oncogene (also known as neu or c-erbB-2) belongs to the epidermal growth factor receptor family. HER2 is frequently amplified in human carcinomas. Gene amplification or overexpression of HER2 has been correlated with poor prognosis in several human cancers. Point mutation in the rat HER2 homolog, neu, is involved in the formation of rat neuroblastomas. However, no similar mutation in HER2 has been found in human cancers. Here we report the identification of a novel alternative splicing form of HER2 (ΔHER2) in human cell lines. An exon 16 amino acids long in the extracellular domain was deleted in ΔHER2. Deletion mutations in the corresponding region were shown previously to be involved in the formation of mammary carcinomas in transgenic mice. In the focus-formation assay, ΔHER2 showed much stronger transformation activity than did wild-type HER2. This result suggests that the deleted 16–amino acid exon may play a regulatory role in HER2 transformation activity. Mol. Carcinog. 23:62–68, 1998. © 1998 Wiley-Liss, Inc.

Nuclear translocation of the pro‐apoptotic Bcl‐2 family member Bok induces apoptosis

Abstract: The anti-apoptotic members of the Bcl-2 family, such as Bcl-2 and Bcl-XL, play a central role in preventing the induction of apoptosis via the intrinsic apoptotic pathway. It has been previously shown that induction of apoptosis by the pro-apoptotic Bcl-2 family member Bok is not antagonized by either Bcl-2 or Bcl-xL, suggesting that Bok might have a unique role in the apoptotic cascade. We showed here that human Bok is the only member of the Bcl-2 family to have a leucine-rich sequence indicative of a nuclear export signal within its BH3 domain. Western blot analysis of nuclear and cytoplasmic fractions identified Bok in both the nucleus and the cytoplasm of HEK 293T cells, HeLa cells, and breast cancer cells, and its nuclear concentration increased after treatment of those cells with leptomycin B, an inhibitor of the exportin Crm1. Immunocytochemistry of flag-tagged Bok confirmed its nuclear localization. Mutating the nuclear export signal of Bok by site-directed mutagenesis resulted in an increase in its nuclear localization and apoptotic activity. We also found that Crm1 interacted with wild-type Bok but not with the mutated form. These results suggest that nuclear export of Bok is a regulated process mediated by Crm1, and constitutes the first report of a link between the apoptotic activity and nuclear localization of a pro-apoptotic member of the Bcl-2 family. © 2005 Wiley-Liss, Inc.

Fatty acid synthase and the lipogenic phenotype in cancer pathogenesis

Abstract: Fatty acid synthase (FASN) catalyses the synthesis of fatty acids, and this synthetic pathway is upregulated in many tumours. How might FASN and increased lipogenesis be involved in cancer, and is FASN a valid therapeutic target? There is a renewed interest in the ultimate role of fatty acid synthase (FASN) — a key lipogenic enzyme catalysing the terminal steps in the de novo biogenesis of fatty acids — in cancer pathogenesis. Tumour-associated FASN, by conferring growth and survival advantages rather than functioning as an anabolic energy-storage pathway, appears to necessarily accompany the natural history of most human cancers. A recent identification of cross-talk between FASN and well-established cancer-controlling networks begins to delineate the oncogenic nature of FASN-driven lipogenesis. FASN, a nearly-universal druggable target in many human carcinomas and their precursor lesions, offers new therapeutic opportunities for metabolically treating and preventing cancer.

The molecular biology of head and neck cancer

Abstract: Head and neck squamous cell carcinomas (HNSCCs) are caused by tobacco and alcohol consumption and by infection with high-risk types of human papillomavirus (HPV). Tumours often develop within preneoplastic fields of genetically altered cells. The persistence of these fields after treatment presents a major challenge, because it might lead to local recurrences and second primary tumours that are responsible for a large proportion of deaths. Aberrant signalling pathways have been identified in HNSCCs and inhibition of epidermal growth factor receptor (EGFR) has proved a successful therapeutic strategy. In this Review, we discuss the recent literature on tumour heterogeneity, field cancerization, molecular pathogenesis and the underlying causative cancer genes that can be exploited for novel and personalized treatments of patients with HNSCC.

WNT signalling pathways as therapeutic targets in cancer

Abstract: Since the initial discovery of the oncogenic activity of WNT1 in mouse mammary glands, our appreciation for the complex roles for WNT signalling pathways in cancer has increased dramatically. WNTs and their downstream effectors regulate various processes that are important for cancer progression, including tumour initiation, tumour growth, cell senescence, cell death, differentiation and metastasis. Although WNT signalling pathways have been difficult to target, improved drug-discovery platforms and new technologies have facilitated the discovery of agents that can alter WNT signalling in preclinical models, thus setting the stage for clinical trials in humans.

Wnt signaling in cancer.

Abstract: Wnt signaling is one of the key cascades regulating development and stemness, and has also been tightly associated with cancer. The role of Wnt signaling in carcinogenesis has most prominently been described for colorectal cancer, but aberrant Wnt signaling is observed in many more cancer entities. Here, we review current insights into novel components of Wnt pathways and describe their impact on cancer development. Furthermore, we highlight expanding functions of Wnt signaling for both solid and liquid tumors. We also describe current findings how Wnt signaling affects maintenance of cancer stem cells, metastasis and immune control. Finally, we provide an overview of current strategies to antagonize Wnt signaling in cancer and challenges that are associated with such approaches.