Andres J.P. Klein-Szanto, MD, PhD
Office Phone: 215-728-3154
Overview of Research Interests
The major areas of research in this laboratory are:
- Identification of molecular mechanisms of tumor progression that are relevant to epithelial cancers
- Investigation of the molecular mechanisms of tobacco-related carcinogenesis in human and experimental malignancies
- Based on the basic molecular work, developing and applying new markers of tumor progression that can be used in clinical studies.
Role of the Pro-protein Convertases (PCs) PACE-4 and Furin During Tumor Progression
Over-expression of PCs correlates with an aggressive neoplastic phenotype both in mouse models and in human primary tumors. This has been demonstrated in our laboratory using tumor cells derived from lung, ovarian and oral malignant tumors. In addition, a transgenic model targeting the expression of PACE4 to squamous epithelia using the bovine keratin 5 promoter (K5-PACE4) (Figure: Diagram of PC functions ) was developed to study carcinogenesis and its inhibition. PCs can be blocked by using competitive inhibitors such as PDX, PC propeptides and chloro-methyl-ketone (CMK)(Figure: PDX inhibition of PC-mediated tumor invasion). The latter inhibitor decreases and even abolishes the invasive/malignant phenotype of tumor cells by inhibiting the activation of invasion and metastasis-associated gene products such as MT1-MMP, stromelysin 3, TGF-β and IGFR1.
CMK was also used in vivo by topical skin administration. This treatment results in decreased epidermal keratinocyte proliferation and a significant decrease in the number of chemically-induced mouse skin cancers (40%) as well as diminished tumor volumes (60%) in wild type and K5-PACE4 transgenic mice. This project also includes the use of other transgenic mice in which furin, PDX and PC propeptides are targeted to the epidermis using the bovine K5 promoter. These studies are aimed at evaluating the increase or decrease in UV-induced skin carcinogenesis in animals overexpressing either PCs or PC inhibitors, respectively.Top
Vsnl-1 (VILIP-1) Expression in Human and Rodent Malignancies
Vsnl-1 is a member of the neuronal Ca++ sensor protein family. Vsnl-1 is able to act as a tumor suppressor in mouse skin squamous carcinoma cells inhibiting cell proliferation, adhesion and invasion by modulating cAMP levels as well as inactivating MMP-9 and RhoA activity.
Since Vsnl-1 is expressed in the basal cells of murine and human bronchial epithelium and it is lost in most human lung cancer cell lines (Figure: Immunohistochemistry of Vsnl-1 in Lung), we are investigating its putative function as a tumor or invasion suppressor gene in human lung tumors. In addition, we are evaluating the mechanisms that regulate Vsnl-1 gene silencing in human non-small cell lung carcinomas (NSCLC). The central hypothesis is that Vsnl-1 expression modulates tumor growth, motility and/or invasiveness of human lung cancer cells. In addition, we are studying the epigenetic mechanisms that seem to be at work during Vsnl-1 gene silencing. The following experiments are underway I) Determine the biological/biochemical mechanisms whereby loss of Vsnl-1 expression may lead to increased malignancy. We are studying small GTPase activation and modulation of locomotion and invasiveness in human NSCLC cell systems in the context of Vsnl-1 regulation of cAMP. The epigenetic silencing of Vsnl-1 in primary lung cancer is also part of this project. This component of the study will ascertain whether tumors of different histological type, histopathological grade, clinical stage, and gender will exhibit different levels of epigenetic silencing. II) Characterization of trans- and cis-acting elements regulating Vsnl-1 expression in human lung cancer cells. We are focusing on the already identified binding sites for the NRF-1 transcription factor present in the Vsnl-1 promoter. The minimal promoter and interactions between transcription factors (NRF-1 and others) and their binding sites on Vsnl-1 promoter will be studied. III) Since preliminary data indicate that histone deacetylase inhibitors (HDACi) induced Vsnl-1 protein expression, we will determine whether HDACi have an effect on tumor cell proliferation and invasiveness and whether this requires the NRF-1 binding site to be intact by using site-specific mutagenesis and dominant negative NRF-1 with and without Vsnl-1 siRNA transfections.Top