Division of Pathology and Laboratory Medicine, Department of Pathology, Unit 085, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.Molecular oncology (Impact Factor: 5.33). 03/2012; 6(2):177-81. DOI: 10.1016/j.molonc.2012.02.007
Molecular pathology as applied to neoplasia is a rapidly expanding component of the discipline of pathology that uses molecular biology tools in addition to conventional morphologic, immunohistochemical and chemical analyses of abnormalities in tissues and cells to understand the etiology and pathogenesis of tumors, establish their diagnosis, and contribute to prognostication and therapeutic decisions for cancer patient care. Biomarkers are a fundamental component of personalized cancer care, and the discipline of molecular pathology therefore contributes throughout the continuum from biomarker research to use in standard-of-care personalized cancer therapy. This brief review addresses some of the specific roles of molecular pathology in that continuum.
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ABSTRACT: The Tn antigen is a tumor-associated carbohydrate antigen that is not normally expressed in peripheral tissues or blood cells. Expression of this antigen, which is found in a majority of human carcinomas of all types, arises from a blockage in the normal O-glycosylation pathway in which glycans are extended from the common precursor GalNAcα1-O-Ser/Thr (Tn antigen). This precursor is generated in the Golgi apparatus on newly synthesized glycoproteins by a family of polypeptide α-N-acetylgalactosaminyltransferases (ppGalNAcTs) and then extended to the common core 1 O-glycan Galβ1-3GalNAcα1-O-Ser/Thr (T antigen) by a single enzyme termed the T-synthase (core 1 β3-galactosyltransferase or C1GalT). Formation of the active form of the T-synthase requires a unique molecular chaperone termed Cosmc, encoded by Cosmc on the X-chromosome (Xq24 in humans, Xc3 in mice). Cosmc resides in the endoplasmic reticulum (ER) and prevents misfolding, aggregation, and proteasome-dependent degradation of newly synthesized T-synthase. Loss of expression of active T-synthase or Cosmc can lead to expression of the Tn antigen, along with its sialylated version Sialyl Tn antigen as observed in several cancers. Both genetic and epigenetic pathways, in addition to potential metabolic regulation, can result in abnormal expression of the Tn antigen. Engineered expression of the Tn antigen by disruption of either C1GalT (T-syn) or Cosmc in mice is associated with a tremendous range of pathologies and engineered expression of the Tn antigen in mouse embryos leads to embryonic death. Studies indicate that many membrane glycoproteins expressing the Tn antigen and/or truncated O-glycans may be dysfunctional, due to degradation and/or misfolding. Thus, expression of normal O-glycans is associated with health and homeostasis whereas truncation of O-glycans, e.g. the Tn and/or Sialyl Tn antigens is associated with cancer and other pathologies.
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ABSTRACT: Background/Aim: Many patients with osteosarcoma (OS) will succumb to distant metastasis, often involving the lungs. Effective therapies for treating lung metastases depend on the availability of a clinically relevant pre-clinical model. Mice were surgically implanted with OS tumor fragments. The time course of primary tumor growth and subsequent spread to the lung were determined. Following development of a lytic and proliferative primary bone lesion, tumor metastasized to the lung in the majority of mice. There was no evidence of tumor at three weeks, but 10 out of 11 mice ultimately developed secondary OS in the lung within 12 weeks. Implantation of OS tumor fragments leads to the development of primary bone tumors and secondary lung metastases, recapitulating the clinical behavior of OS. This model offers an advantage over cell suspension injection models by precluding initial seeding of the lung with tumor cells.