Viji Shridhar Ph.D.

Recipient of the Felice Lipit Jentis Memorial/Joan’s Legacy Research Grant. Funded equally by Joan's Legacy and The Felice Lipit Jentis Memorial BAC Research Trust.

Lay Description

Lung cancer is the leading cause of cancer deaths in the United States. Bronchioalveolar carcinoma (BAC) is a type of lung cancer that is more likely to strike patients who are young, female and non-smokers. As seen in other cancers, BAC is characterized by the overactivity of multiple growth factor signaling cascades. Growth factors interact with receptors on or in the cell, changing the activity of several cellular proteins that then affect cellular structure and physiology. Several of these factors depend on the structure of the extracellular matrix (ECM), a complex mixture of proteins and glycoproteins that surround cells. Far from just holding cells together, the ECM modifies the activity of a number of growth factor signaling cascades. One modification mechanism depends on the sulfation state of ECM proteins. The sulfation state is, in turn, dependent on the expression of a protein called HSulf-1. HSulf-1 removes specific sulfates from the ECM, thereby reducing the signaling of several growth factor cascades. Loss of HSulf-1, on the other hand, promotes growth factor signaling leading to tumor growth, invasion and resistance to chemotherapy. The epidermal growth factor (EGF) signaling cascade is frequently overactive in BAC. Therapy with the new tyrosine kinase inhibitor (TKI) drugs erlotinib and gefitinib, which target the EGF pathway, has proven dramatically successful in some patients with BAC. Specific mutations within the EGF receptor are usually found in patients that respond to TKI’s, although the correlation is not 100%. The role of HSulf-1 in BAC is not known although two of two BAC cell lines have lost HSulf-1 expression. In addition to tumorigenesis, loss of HSulf-1 has been correlated with invasion in head and neck squamous cell carcinomas and resistance to chemotherapy in ovarian and breast carcinomas. The main objectives of this proposal are to 1) Determine the mechanism of loss of HSulf-1 in 150 BACs, 2) Determine whether HSulf-1 expression correlates with the clinical behavior of BACs in these 150 tumors, with particular attention to tumor spread, recurrence and response to TKIs and finally, 3) Determine if HSulf-1 expression is a predictive marker for TKI response. Understanding the role of HSulf-1 in BAC biology will better define potential mechanisms of drug resistance and invasion in BAC and assess methods to overcome them.

Scientific Abstract

Bronchioalveolar carcinoma (BAC) is a subset of lung adenocarcinoma with unique biology in that it more often occurs in young, female and non-smoking patients than other types of lung cancer. BAC has a histologic spectrum from pure BAC (PBAC) to BAC with focal invasion (BWFI) and adenocarcinoma with BAC features (AWBF). The epidermal growth factor receptor (EGFR) is over-expressed or mutated in most cases of lung cancer including BAC. The EGFR plays a pivotal role in lung cancer development and progression, influencing cell proliferation, regulation of apoptotic cell death, angiogenesis and metastasis. This growth factor signaling pathway is the target of small molecule tyrosine kinase inhibitors (TKI) erlotinib and gefitinib. In addition to EGFR, other genes are aberrantly expressed in lung adenocarcinomas. Our recent analysis indicates that 16 of 19 (84%) lung adenocarcinoma cell lines have reduced or lost HSulf-1 expression, including complete loss in two of two BAC cell lines. HSulf-1 expression is silenced by promoter methylation and histone deacetylation as treatment of H358 and H650 BAC cell lines with 5-aza-cytidine and LBH-598 (Novartis) resulted in re-induction of HSulf-1 transcription. HSulf1 is an arylsulfatase that selectively removes the 6-O-sulfate from heparan sulfate proteoglycans. Loss of HSulf-1 results in increased signaling by heparin-binding growth factors (HB-GF) such as heparin-binding epidermal growth factor (HB-EGF). In addition to modulating EGFR signaling, HSulf-1 modulates signaling by other HB-GFs such as Fibroblast Growth Factor, Hepatocyte Growth Factor (HGF) and Vascular Endothelial Growth Factor-A, thereby attenuating downstream Erk activation. In vitro, HSulf-1 transfected cells proliferate slower and are more sensitive to cisplatin and taxol than their HSulf-1-deficient counterparts in ovarian, breast and hepatocellular cell lines. Our data in squamous cell carcinoma of the head and neck indicated that loss of HSulf-1 is also involved in promoting HGF-mediated invasion and migration of cancer cells. Thus, HSulf-1 could be a marker of risk for developing other BAC nodules in the same or the contra-lateral lung. Furthermore, modulation of EGFR signaling by HSulf-1 may render these tumors sensitive to EGFR inhibition. In a recent study it was reported that only 23% of the patients with BAC responded to erlotinib. High level of phosphorylated Mitogen-Activated Protein Kinase (MAPK), part of the MAPK/Erk pathway, was the only parameter that was predictive of poor survival. The main objectives of this proposal are to 1) Determine the mechanism of loss of HSulf-1 in 150 primary BACs consisting of a) 50 PBAC, b) 50 BWFI and c) 50 AWBF, 2) Determine whether HSulf-1 expression correlates with clinical behavior of BACs in these 150 tumors. HSulf-1 expression will also be correlated with sulfation state of HSPGs with 10E4 staining, a sulfation specific anti HSPG antibody, 3) Determine whether HSulf-1 expression is a predictive marker for TKI response. Using BAC cell lines with and without HSulf-1 expression, we will determine whether a) the presence of HSulf-1 confers sensitivity to cisplatin and taxol induced cytotoxicity b) Evaluate the cytotoxicity of TKI as single agents when applied to parental vs. HSulf-1 transfected clones in vitro. C) Evaluate the effects of TKIs in combination with cisplatin, paclitaxel, topotecan and gemcitabine in vitro.