Clinical Significance of the Genetic Landscape of Pancreatic Cancer and Implications for Identification of Potential Long-term Survivors

Abstract

Purpose Genetic alterations of KRAS, CDKN2A, TP53 and SMAD4 are the most frequent events in pancreatic cancer. We determined the extent to which these four alterations are coexistent in the same carcinoma, and their impact on patient outcome. Experimental Design Pancreatic cancer patients who underwent an autopsy were studied (n=79). Matched primary and metastasis tissues were evaluated for intragenic mutations in KRAS, CDKN2A and TP53 and immunolabeled for CDKN2A, TP53 and SMAD4 protein products. The number of altered driver genes in each carcinoma was correlated to clinicopathologic features. Kaplan-Meier estimates were used to determine median disease free and overall survival, and a Cox proportional hazards model used to compare risk factors. Results The number of genetically altered driver genes in a carcinoma was variable, with only 29 patients (37%) having an alteration in all four genes analyzed. The number of altered driver genes was significantly correlated with disease free survival (p=0.008), overall survival (p=0.041) and metastatic burden at autopsy (p=0.002). On multivariate analysis, the number of driver gene alterations in a pancreatic carcinoma remained independently associated with overall survival (p=0.046). Carcinomas with only one to two driver alterations were enriched for those patients with the longest survival (median 23 months, range 1–53). Conclusions Determinations of the status of the four major driver genes in pancreatic cancer, and specifically the extent to which they are coexistent in an individual patients cancer, provides distinct information regarding disease progression and survival that is independent of clinical stage and treatment status.

Early diagnosis of pancreatic cancer: Current trends and concerns

“…These observations should support a genetic progression model of pancreatic carcinogenesis leading to invasive cancer 5, 6, 7, 8, 9, 10. Recently, the estimated lifetime of clonal evolution during PC development and progression based on a computational model using many autopsy cases has been reported 11, 12. This model suggested an average of 11.7 years from the initiating carcinogenesis until development of the parental clone, an average of 6.8 years to the development of metastatic subclones within the primary PC, and an average of 2.7 years until death of the case (Figure 1).…”

Development of bioluminescent chick chorioallantoic membrane (CAM) models from primary pancreatic cancer cells: A platform for drug testing

“…In particular, the genetic landscape of PDAC is notable for four frequently mutated genes, classifiable as "driver" genes, including K-RAS, TP53, CDKN2A/p16INK4a, and SMAD4/DPC4. These four genes are well recognized as contributing to the carcinogenesis and maintenance of PDAC, and the simultaneous determination of their status provides important information regarding disease progression and survival 16 . DNA extracted from frozen samples was successfully amplified in 100% of all the original human tumors and CAM tumors specimens, for each studied exon.…”

“…We used 20 ng of genomic DNA, as template in nested PCR reactions to amplify DNA fragments corresponding to exons 1 and 2 of K-RAS, TP53 exons 5-9, CDKN2A/p16INK4a exons 1 and 2, and DPC4/SMAD4 exons 0-11. The PCR protocol and the sets of primers have been described in detail previously 16,48 . PCR products were purified using a presequencing kit (Amersham Biosciences, Roosendaal, The Netherlands) and sequenced with both forward and reverse primers using the BigDyeTM Terminator v3.1 Cycle Sequencing Kit (Applied Biosystems, Foster City, CA), with the ABI PRISMTM 3100 Genetic analyzer (Applied Biosystems).…”

“…Additional IHC studies were performed using antibodies to Cdkn2A (clone E6H4, MTM Laboratories, Heidelberg, Germany), p53 (Bp-53-11, Ventana) and Smad4 (clone B8, Santa Cruz Biotechnology, Santa Cruz, CA) proteins, as reported previously 16 . Nuclear labeling of Cdkn2A was scored as intact (positive, indicating the presence of an intact gene) or lost (negative, indicating a deletion, inactivating mutation or promoter hypermethylation); p53 immunolabeling was considered abnormal when it showed nuclear accumulation of this protein in ≥ 30% of the neoplastic cells compared to adjacent normal cells, or if the neoplastic cells showed a virtual absence of immunolabeling compared to immediately adjacent normal cells suggesting the presence of an intragenic deletion, nonsense or frameshift mutation; nuclear labeling of Smad4 was scored as intact (positive, indicating the presence of an intact gene) or lost (negative, indicating a deletion or inactivating mutation of the gene has occurred).…”

Improving Survival of Pancreatic Cancer. What Have We Learnt?

“…Yachida et al [111] demonstrated that among patients with stage I/II disease who had two driver gene alterations, the median disease-free and median overall survival was longer. Also, these patients were significantly more likely to develop oligometastatic failure.…”