Pedram Argani

The phosphatidylinositol 3-kinases (PI3Ks) are known regulators of cellular growth and proliferation. It has recently been reported that somatic mutations within the PI3K subunit p110alpha (PIK3CA) are present in human colorectal and other cancers. Here we show that thirteen of fifty-three breast cancers (25%) contain somatic mutations in PIK3CA, with the majority of mutations located in the kinase domain. These results demonstrate that PIK3CA is the most mutated oncogene in breast cancer and support a role for PIK3CA in epithelial carcinogenesis.

Infiltrating adenocarcinomas of the pancreas are believed to arise from histologically identifiable intraductal precursors [pancreatic intraepithelial neoplasias (PanINs)] that undergo a series of architectural, cytological, and genetic changes. The role of DPC4 tumor suppressor gene inactivation in this progression has not been defined. Immunohistochemistry for the Dpc4 protein in formalin-fixed, paraffin-embedded tissue is a sensitive and specific marker for DPC4 gene status, providing a tool to examine DPC4 status in these putative precursor lesions. A total of 188 PanINs were identified in 40 pancreata, 38 (95%) of which also contained an infiltrating adenocarcinoma. Sections containing these 188 duct lesions were labeled with a monoclonal antibody to Dpc4. All 82 flat (PanIN-1A), all 54 papillary (PanIN-1B), and all 23 atypical papillary (PanIN-2) intraductal lesions expressed Dpc4. In contrast, 9 of 29 (31%) severely atypical lesions (PanIN-3 lesions, carcinomas in situ) did not. The difference in Dpc4 expression between histologically low-grade (PanIN-1 and -2) and histologically high-grade (PanIN-3) duct lesions was statistically significant (P < 0.0001). In three cases, the pattern of Dpc4 expression in the PanIN-3 lesions did not match the pattern of expression in the associated infiltrating carcinomas, indicating that these high-grade lesions did not simply represent infiltrating carcinoma growing along benign ducts. Loss of Dpc4 expression occurs biologically late in the neoplastic progression that leads to the development of infiltrating pancreatic cancer, at the stage of histologically recognizable carcinoma.

Michael C. Haffner 1 , Alcides Chaux 2 , Alan K. Meeker 1,2,3 , David M. Esopi 1 , Jonathan Gerber 4 , Laxmi G. Pellakuru 2 , Antoun Toubaji 2 , Pedram Argani 1,2 , Christine Iacobuzio-Donahue 1,2 , William G. Nelson 1,2,3 , George J. Netto 1,2,3 , Angelo M. De Marzo 1,2,3 , Srinivasan Yegnasubramanian 1 1 Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, Maryland, USA 2 Department of Pathology, Johns Hopkins University, Baltimore, Maryland, USA 3 Brady Urological Institute, Johns Hopkins University, Baltimore, Maryland, USA 4 Department of Medicine, Division of Hematology, School of Medicine, Johns Hopkins University, Baltimore, Maryland, USA Received: September 1, 2011; Accepted: September 1, 2011; Published: September 2, 2011; Keywords: 5-hydroxymethylcytosine, 5hmC, DNA methylation, differentiation, cancer, tissue stem / progenitor cells Correspondence: Srinvasan Yegnasubramanian, email: // // Abstract DNA methylation at the 5-position of cytosines (5mC) represents an important epigenetic modification involved in tissue differentiation and is frequently altered in cancer. Recent evidence suggests that 5mC can be converted to 5-hydroxymethylcytosine (5hmC) in an enzymatic process involving members of the TET protein family. Such 5hmC modifications are known to be prevalent in DNA of embryonic stem cells and in the brain, but the distribution of 5hmC in the majority of embryonic and adult tissues has not been rigorously explored. Here, we describe an immunohistochemical detection method for 5hmC and the application of this technique to study the distribution of 5hmC in a large set of mouse and human tissues. We found that 5hmC was abundant in the majority of embryonic and adult tissues. Additionally, the level of 5hmC closely tracked with the differentiation state of cells in hierarchically organized tissues. The highest 5hmC levels were observed in terminally differentiated cells, while less differentiated tissue stem/progenitor cell compartments had very low 5hmC levels. Furthermore, 5hmC levels were profoundly reduced in carcinoma of the prostate, breast and colon compared to normal tissues. Our findings suggest a distinct role for 5hmC in tissue differentiation, and provide evidence for its large-scale loss in cancers.