Biomedical subjects

R Przygodzki

Publications and source records attributed to R Przygodzki.

4 recordsLinked to original sources

PubMed1999

Loss of heterozygosity at 1p36 predicts poor prognosis in gastrointestinal stromal/smooth muscle tumors.

Gastrointestinal stromal/smooth muscle tumors are uncommon neoplasms for which current criteria for diagnosing malignancy (size and mitotic index) sometimes fail to predict outcome. Cytogenetic studies reveal frequent chromosome 1 abnormalities in these tumors, but significant underlying molecular changes have not been elucidated, and their significance is unknown. DNA was obtained from the formalin-fixed, paraffin-embedded tissue of 80 gastrointestinal stromal/smooth muscle tumors. Tumors were topographically microdissected from surrounding normal tissue; microsatellite markers from tumor and normal tissue were amplified by PCR in the regions of chromosome 1p36 (D1S199, D1S228, D1S450, D1S214, D1S243), 1p12 (D1S418),1p13 (D1S252, D1S514), and 1q32(D1S103). The presence or absence of heterozygosity for each case was mapped at each informative marker. Relationships among loss of heterozygosity (LOH), tumor size, mitotic index, and survival were investigated using correlation analysis, Kaplan-Meier plots, and the Cox model. LOH at 1p36 was found in 24 of 80 cases, suggesting the possibility of a tumor suppressor gene at 1 p36 near the site of a suspected neuroblastoma tumor suppressor gene. Patients whose tumors demonstrated LOH at 1 p36 had significantly shorter survival (p = 0.017) than those whose tumors did not. LOH at 1 p36 retained independent prognostic significance in a multivariate model that included KIT mutation status and tumor size; the mitotic index, however, did not retain independent significance in such a model. LOH was observed at 1 p12-1p13 (most frequently at 1p13.3) in 19 of 80 cases, but loss of heterozygosity at this site did not influence survival. No LOH was observed near 1q32. These findings provide strong evidence for a prognostically significant tumor suppressor gene in the region of chromosome 1p36.3.

Base Sequence↗

PubMed1998

Microdissection-Based p53 Genotyping: Concepts for Molecular Testing.

p53 is the most commonly altered tumor-suppressor gene in humans, involved in the development and progression of many diverse forms of human cancer. Although much remains to be learned about the biology of this important growth regulatory gene, sufficient experience has been accumulated with respect to the occurrence and pattern of p53 mutational change to justify molecular diagnostic testing for specific objectives. The authors outline specific concepts for testing with particular emphasis for solid tumor molecular diagnostics. This article focuses on microdissection-based fixed tissue molecular analysis, introducing new considerations related to quality control appropriate for this type of methodology. Given the rapidly evolving nature of molecular genetics, the suggestions provided here should be viewed as flexible. Nevertheless, the concepts are intended to serve as a model for other oncogene/tumor suppressor-gene assays to be developed with the overall purpose of establishing informative integrated histopathologic/genetic molecular diagnostic testing to complement standard microscopic analysis.

Journal Article↗

PubMed1996

Prediction of Biologic Aggressiveness in Colorectal Cancer by p53/K-ras-2 Topographic Genotyping.

Background: Topographic genotyping is a system of solid tissue molecular analysis designed to correlate microscopic alterations with specific forms of gene damage. In this system, microscopic targets are selected on the basis of cellular and immunohistochemical features. Minute tissue samples corresponding to these targets are precisely removed and analyzed for the presence and specific type of oncogene/tumor suppressor gene damage by means of polymerase chain reaction (PCR) followed by DNA sequencing. In this study, topographic genotyping was used to investigate the prognostic value of p53 and K-ras-2 mutational damage in 204 patients with colorectal cancer from two tertiary care centers. Methods and Results: The intensity and distribution of p53 immunohistochemical staining were correlated with the presence and specific type of mutational change, which resulted in a better understanding of the highly variable nature of p53 immunostaining patterns. Molecular genotype was correlated with the depth and extent of colorectal cancer spread (Dukes B and C) and with survival for follow-up periods of up to 10 years. An algorithm for p53/K-ras-2 genotyping was formulated to include p53 immunohistochemistry and DNA sequencing both of p53 exons 5-8 and of K-ras-2 exons 1 and 2. By using this algorithm, survival was shown to be significantly better in those patients whose tumors manifested normal p53 and K-ras-2 genes (P >.01). Patients with p53-mutated tumors composed a poor prognostic group, characterized by a high rate of intra-abdominal recurrence in the form of peritoneal seeding. Patients with K-ras-2-mutated tumors also composed a poor prognostic group, marked by a tendency for distant hematogenous metastasis involving lung, bone, and brain. Conclusions: Topographic genotyping's molecular diagnostic approach to colorectal cancer combines immunohistochemistry, PCR, and DNA sequencing. It is informative, cost-effective, timely, and yet fully integrated with standard histopathology. The use of this approach by pathologists as a model system for molecular diagnosis of colorectal cancer and other forms of solid tumor malignancy is recommended. As new prognostic molecular lesions are documented for tumor progression and metastasis, topographic genotyping will be well suited to facilitate their clinical application.

Journal Article↗

PubMed1994

K-ras-2 topographic genotyping of pancreatic adenocarcinoma.

OBJECTIVE: To determine the frequency distribution of K-ras-2 point mutation genotypes in pancreatic adenocarcinoma and to evaluate the effectiveness of K-ras-2 genotyping as a means to predict localized disease and potential long-term survival. DESIGN: Topographic genotyping from archival formalin-fixed, paraffin-embedded large- and biopsy-sized tissue specimens as well as cytologic fluid using polymerase chain reaction products and direct sequencing together with clinicopathologic and statistical analysis. SETTING: Tertiary care medical center with molecular diagnostics pathology laboratory. PATIENTS: Patients treated between 1988 and 1993 at Rhode Island Hospital, Providence, yielding 55 primary and 56 metastatic specimens of pancreatic adenocarcinoma. RESULTS: Each primary pancreatic adenocarcinoma was found to contain one of eight specific genotypes that was maintained in all metastatic deposits of that individual tumor. Primary adenocarcinomas confined to the pancreatic bed at diagnosis were predominantly of a normal genotype (56% [14/25]). Pancreatic adenocarcinomas progressing to distant hematogenous metastasis were almost exclusively mutated (88% [7/8]; P < .005). Patients undergoing pancreatic resection (Whipple's operation) and having a normal K-ras-2-genotype (58% [11/19]) had a significantly longer survival (21.3 months) than similar patients with mutated tumors (8.2 months). CONCLUSIONS: The findings support the feasibility of K-ras-2 topographic genotyping to identify potentially indolent disease and suggest a potentially useful role in the preoperative evaluation of pancreatic adenocarcinoma.

Adenocarcinoma↗