BRAF and FBXW7 (CDC4, FBW7, AGO, SEL10) mutations in distinct subsets of pancreatic cancer: potential therapeutic targets.

The recognition of biologically distinct tumor subsets is fundamental to understanding tumorigenesis. This study investigated the mutational status of the serine/threonine kinase BRAF and the cyclin E regulator FBXW7 (CDC4, FBW7, AGO, SEL10) related to two distinct pancreatic carcinoma subsets: the medullary KRAS2-wild-type and the cyclin E overexpressing tumors, respectively. Among KRAS2-wild-type carcinomas, 33% (3 of 9) contained BRAF V599E mutations; one of which was identified in the pancreatic cancer cell line COLO357. Among 74 KRAS2-mutant carcinomas, no BRAF mutations were identified. Among the KRAS2/BRAF wild-type carcinomas, no mutations within pathway members MEK1, MEK2, ERK1, ERK2, RAP1B, or BAD were found. Using pancreatic cancer microarrays and immunohistochemistry, we determined that 6% (4 of 46 and 5 of 100 in two independent panels) of pancreatic adenocarcinomas overexpress cyclin E. We identified two potential mechanisms for this overexpression including the amplification/gain of CCNE1 gene copies in the Panc-1 and Su86.86 cell lines and a novel somatic homozygous mutation (H460R, in one of 11 pancreatic cancer xenografts having allelic loss) in FBXW7, which was accompanied by cyclin E overexpression by immunohistochemistry. Both BRAF and FBXW7 mutations functionally activate kinase effectors important in pancreatic cancer and extend the potential options for therapeutic targeting of kinases in the treatment of phenotypically distinct pancreatic adenocarcinoma subsets.

Exploration of global gene expression patterns in pancreatic adenocarcinoma using cDNA microarrays.

Pancreatic cancer is the fifth leading cause of cancer death in the United States. We used cDNA microarrays to analyze global gene expression patterns in 14 pancreatic cancer cell lines, 17 resected infiltrating pancreatic cancer tissues, and 5 samples of normal pancreas to identify genes that are differentially expressed in pancreatic cancer. We found more than 400 cDNAs corresponding to genes that were differentially expressed in the pancreatic cancer tissues and cell lines as compared to normal pancreas. These genes that tended to be expressed at higher levels in pancreatic cancers were associated with a variety of processes, including cell-cell and cell-matrix interactions, cytoskeletal remodeling, proteolytic activity, and Ca(++) homeostasis. Two prominent clusters of genes were related to the high rates of cellular proliferation in pancreatic cancer cell lines and the host desmoplastic response in the resected pancreatic cancer tissues. Of 149 genes identified as more highly expressed in the pancreatic cancers compared with normal pancreas, 103 genes have not been previously reported in association with pancreatic cancer. The expression patterns of 14 of these highly expressed genes were validated by either immunohistochemistry or reverse transcriptase-polymerase chain reaction as being expressed in pancreatic cancer. The overexpression of one gene in particular, 14-3-3 sigma, was found to be associated with aberrant hypomethylation in the majority of pancreatic cancers analyzed. The genes and expressed sequence tags presented in this study provide clues to the pathobiology of pancreatic cancer and implicate a large number of potentially new molecular markers for the detection and treatment of pancreatic cancer.

The desmoplastic response to infiltrating breast carcinoma: gene expression at the site of primary invasion and implications for comparisons between tumor types.

The gene expression patterns of desmoplasia are becoming exposed through the application of global gene expression technologies such as cDNA microarrays or serial analysis of gene expression (SAGE). These patterns represent the sum of the many cellular components of the host stromal response to an infiltrating carcinoma. In studies of human neoplasms, it would be useful to identify those prototypical genes that characteristically indicate the recognizable forms of the responses to individual tumor types. Such genes may offer clues to better understand the process of invasion itself, the interactions between tumor and host cells, and tumor-specific differences in invasion. We used SAGE-defined genes and in situ transcript labeling to characterize the desmoplastic stroma induced by infiltrating ductal carcinomas of the breast. Principal component analysis identified 103 SAGE tags as specific for invasive breast carcinomas, in comparison with in situ duct carcinomas or normal breast epithelium. Of these, 68 tags corresponded to known genes. Six of the 68 genes from this breast cancer "invasion-specific" cluster were further characterized by in situ hybridization to breast cancer tissues. Results of in situ hybridization demonstrated that each gene was expressed within one of five distinct regions of the invasive tumors (neoplastic epithelium; angioendothelium; inflammatory, panstromal, and juxtatumoral stroma), reflecting a defined architectural structure to the transcriptome of invasive breast cancers. Two of these 6 genes were specifically expressed by the stromal cells within the invasive carcinoma; however, 1 (collagen 1alpha1) was expressed throughout the stromal response (panstromal expression), whereas the second (osteonectin) was specifically expressed within the juxtatumoral stromal cells, indicating a critical "regionality" of gene expression within the stromal response itself. A comparison of the gene expression profiles of the juxtatumoral stroma in breast and pancreatic carcinomas indicated important differences between the two, suggesting tumor-specific or organ-specific differences in the desmoplastic responses. Some of the genes presented are novel markers of the invasive process, imply communication at the host/tumor interface, and suggest potential therapeutic targets.

Relationships and differentially expressed genes among pancreatic cancers examined by large-scale serial analysis of gene expression.

Pancreatic adenocarcinoma is among the most fatal of cancers, in part because of late diagnosis and a lack of effective therapies. Comprehensive studies are needed to better understand and address the cellular mechanisms and pathways of tumorigenesis. Serial analysis of gene expression was used to analyze gene expression profiles of pancreatic cancer cell lines, short-term cultures of normal pancreatic ductal epithelium, and primary pancreatic cancer tissue. A total of 294,920 tags representing 77,746 genes in 10 serial analysis of gene expression libraries were analyzed. A pancreatic cancer cell line (Hs766T) that exhibited a "normoid" profile of gene expression was identified. Several genes that may be involved in the fundamental nature of malignant changes in pancreatic ductal epithelium were suggested from those differentially and highly expressed in pancreatic cancer cells as compared with normal epithelium. Some overexpressed genes, such as S100A4, prostate stem cell antigen, carcinoembryonic antigen-related cell adhesion molecule 6, and mesothelin, suggest potential use as diagnostic markers. Others suggest potential novel therapeutic targets.