Bronchioalveolar carcinoma (BAC) is a distinct subtype of non-small cell lung cancer (NSCLC), the latter the most common form of lung cancer. Its incidence has been the subject of much debate with some studies arguing BAC is the rise and may now comprise up to 20% of all lung cancers. This controversy may reflect the decision by the WHO in 1999 to restrict the diagnosis of BAC to non invasive lung cancers growing along the alveolar walls of the lung in a lepidic growth pattern. Pure BAC is rare, comprising 3 4% of lung cancers, as contrasted with the vast majority of BACs seen in the clinic, which are mixed tumors exhibiting varying degrees of invasiveness.

While BAC is primarily a tobacco-related disease, it occurs disproportionately in non smokers and women, raising intriguing questions about its tumor biology. Tumors of non smokers lack the genetic mutations induced by tobacco carcinogens, and therefore make for a more simplified model for studying BAC. BAC is typically diagnosed at an advanced stage when surgery is not an option and also appears chemo-insensitive. This underscores the urgent need to elucidate its tumor biology and to develop novel targeted therapies against the disease.

Wnt proteins comprise a family of highly conserved secreted signaling molecules regulating cell to-cell interactions. Wnt expression initiates pathways leading to transcription of cell proliferation signals through cytosolic pooling of ß-catenin and inhibition of apoptosis. Our group has previously demonstrated that Wnt 1, Wnt-2, and Wnt 16 genes are overexpressed in lung adenocarcinoma and that Wnt signaling is overactivated downstream in the pathway. Our preliminary data showed marked overexpression, compared with normal lung, of Wnt-1 and Wnt-2 genes in a set of BAC tumor specimens. When treated with Wnt-1 and Wnt-2 monoclonal antibodies, and RNAi, we observed decreased cell proliferation and induction of apoptosis in both lung cancer and BAC cell lines.

We propose to analyze expression patterns of Wnt signaling in human BAC tumor specimens and to identify candidate genes as putative therapeutic targets. We will isolate tumor RNA through laser capture microdissection from more than 100 snap frozen samples of surgically-resected BAC currently stored in the Thoracic Oncology Tumor Bank at UCSF. We will then amplify RNA from tumor and matched normal lung using sense RNA amplification technology, and perform an analysis with Wnt microarrays consisting of Wnt 1-19 isoforms, and downstream signals including Wif, Dvl, ß-catenin, and Survivin. We expect to confirm the presence of aberrant Wnt signaling in BAC. We anticipate that a subset of Wnt pathway genes, most notably Wnt-1, Wnt-2 will be abnormally expressed, confirming our preliminary data. We propose to identify genes that are consistently overexpressed in BAC and validate them using RT-PCR and Western blotting techniques. We will then develop monoclonal antibodies and siRNA, testing them for efficacy in vitro in BAC cell lines. Finally, we will develop expression profiles correlated with BAC histology and match them to our clinical database based on patient characteristics and clinical course.