Federico Innocenti Ph.D.

With funding from the Sandra Phillips Britt Fund for Lung Cancer Research.

Lay Description

The treatment of patients with bronchioalveolar carcinoma (BAC) is far from optimal and new strategies to improve the survival of these patients are needed. One way to increase the chance of response in BAC patients is to understand the mechanisms behind the uncontrolled growth of cancer cells. In adenocarcinomas, one of those mechanisms has been studies in details, leading to the successful approval of drugs inhibiting this mechanism.

This mechanism is called “angiogenesis”, such as the formation of new blood vessels that bring “food” to the growing tumors. The role of angiogenesis in BACs remains to be investigated. One of the key proteins driving the growth of new blood vessels in tumors is the vascular endothelial growth factor receptor 2 (VEGFR-2). In this application, we aim to study the biology of VEGFR-2 to see how the activity and level of this protein varies in different BACs. More importantly, we will evaluate whether there is a genetic basis for the differences in VEGFR-2 levels observed in patients with BACs.

We have previously discovered that the VEGFR-2 gene is highly variable in the general population, and we hypothesize that these genetic variations might affect the level and function of VEGFR-2 in BACs. For testing these hypotheses, we will evaluate the effect of the variation in VEGFR-2 gene on the expression of the VEGFR-2 protein in BACs. We will also test their effect on the amount of angiogenesis in these tumors. In addition, we will use cell line models in vitro to further establish the role of the VEGFR-2 gene variants at a cellular level.

The ultimate aim of this proposal is to use this information to improve the cure of BAC patients by identifying those patients that might benefit from angiogenesis inhibitors according to their genetic make up of the VEGFR-2 gene.

Scientific Abstract

BAC is a subtype of adenocarcinoma with a pure bronchioalveolar growth pattern and no evidence of stromal, vascular, or pleural invasion. The biology of EGFR has been studied intensively in BACs, but the role of angiogenesis in this subtype is not well understood. In solid tumor angiogenesis, VEGF and VEGFR-2 are regarded as the most critical endothelial cell ligand and receptor, respectively. The role of angiogenesis in tumor progression of NSCLC adenocarcinomas is well established, and a clear correlation exists between VEGF and VEGFR-2 overexpression, microvessel density (MVD) and impaired prognosis in NSCLC. VEGFR-2 is the most important receptor of VEGF; it stimulates endothelial cell proliferation and migration via its tyrosine kinase activity and mediates all endothelial cell responses to VEGF to establish a tumor’s neovasculature.

We have generated preliminary data on the genetic variation of the VEGFGR-2 gene. According to our data, a promoter variant (-271G>A) dramatically reduces the luciferase activity of VEGFR-2. Out of the nonsynonymous variants changing the amino acid sequence, 4 have been predicted to have a deleterious effect of the VEGFR-2 function. These variants have been found both in germline and NSCLC DNA (no tumor somatic variants have been found). Hence, we hypothesize that 1) the variability in VEGFR-2 expression in BACs might be, in part, genetically determined, and 2) nonsynonymous variants might alter the VEGF-mediated activation of VEGFR-2, ultimately resulting in differences in MVD in BACs and in differences in VEGFR-2 phosphorylation at cellular level. For testing these hypotheses, we will use 70 pure BAC and BAC with adenocarcinoma features (1:1 ratio) chosen from our tissue bank. Samples will be stained for VEGFR-2 and tissue microarrays will be prepared for MVD staining. Then the association between the presence of the promoter variant and differences in VEGFR-2 staining and MVD will be evaluated in the BAC samples. The association between the 4 nonsynonuymous variants and MVD will be also tested in the same BAC samples. In addition, we will also use the NIH-3T3 cell line to investigate the effect of 4 the nonsynonymous variants of VEGFR-2 phosphorylation.

The identification of molecular markers of response to select therapies in cancer patients remains an unsolved issue for most of the common tumor types. VEGFR-2 might play an important role in the biology of BACs, and this study provides the scientific foundation for testing role of VEGFR-2 gene variants in BAC patients. Specifically, such variants might be prognostic and/or predictive of response. Hence, ultimately, such variants might be used to select those BAC patients who might benefit from the treatment with anti-angiogenesis inhibitors.