Familial pancreatic cancer: genetic advances

Beset by poor prognosis, pancreatic ductal adenocarcinoma is classified as familial or sporadic. This review elaborates on the known genetic syndromes that underlie familial pancreatic cancer, where there are opportunities for genetic counseling and testing as well as clinical monitoring of at-risk patients. Such subsets of familial pancreatic cancer involve germline cationic trypsinogen or PRSS1 mutations (hereditary pancreatitis), BRCA2 mutations (usually in association with hereditary breast–ovarian cancer syndrome), CDKN2 mutations (familial atypical mole and multiple melanoma), or DNA repair gene mutations (e.g., ATM and PALB2, apart from those in BRCA2). However, the vast majority of familial pancreatic cancer cases have yet to have their genetic underpinnings elucidated, waiting in part for the results of deep sequencing efforts.     

Myeloperoxidase G-463A polymorphism and lung cancer: a HuGE genetic susceptibility to environmental carcinogens pooled analysis.

Myeloperoxidase is a phase I metabolic enzyme that converts the metabolites of benzo[a]pyrene from tobacco smoke into highly reactive epoxides. A polymorphism in the promoter region of myeloperoxidase (463G-->A) has been found to be inversely associated with lung cancer; differences in the association with age and gender have been suggested. We conducted a pooled analysis of individual data from 10 studies (3688 cases and 3874 controls) from the Genetic Susceptibility to Environmental Carcinogens database. The odds ratio for lung cancer was 0.88 (95% confidence interval: 0.80-0.97) for the AG variant of myeloperoxidase G-463A polymorphism, and 0.71 (95% confidence interval: 0.57-0.88) for the AA variant after adjusting for smoking, age, gender, and ethnicity. The inverse association between lung cancer and myeloperoxidase G-463A polymorphism was equally found in males and females (odds ratio for the AA genotype 0.73 [95% confidence interval: 0.56-0.96] and 0.67 [95% confidence interval: 0.46-0.98], respectively), without differences in the association according to age in the two genders. The myeloperoxidase G-463A polymorphism was significantly protective in "ever" smokers but not in "never" smokers. Myeloperoxidase is a key enzyme in tobacco-induced carcinogenesis.     

胰腺癌基因诊断研究进展

目的 探讨对胰腺癌诊断有意义的基因指标。方法 复习国外有关胰腺癌基因诊断方面的文献。结果 K-ras、p53、DPC和端粒酶基因可用于胰腺癌临床诊断。结论 胰腺癌相关基因的检测可用于胰腺癌的早期诊断。     

Extensive genetic alterations in prostate cancer revealed by dual PCR and FISH analysis

The genetic alterations that underlie prostate tumorigenesis are assumed to comprise gain or loss of specific chromosomal regions, whole chromosomes, or sequence-specific mutations. Existing data have not demonstrated clear specificity of whole chromosome or regional chromosomal gain or loss that characterizes entire individual malignant lesions, or all malignant lesions, within a cancerous prostate. We have analyzed tissues from 13 patients for target sequences by using PCR and FISH techniques on paired malignant or prostatic intraepithelial neoplastic (PIN) and benign samples (usually from different areas of the same paraffin section). We exercised stringent histologic control over these samples by examining small ( < 5 mm²), discrete regions of sectioned benign, malignant, and PIN tissue. The same histologic region was examined on serial sections by FISH and PCR analysis. The tissues were examined for numerical aberrations involving chromosomes 4 (as a control), 7, 8, 10, and the Y by FISH analysis, and for gain or loss of chromosome 7 and chromosomal arms 8p, 10q, and Yp by PCR analysis. The concurrent application of PCR and FISH to microdissected prostatic tissues yielded evidence of higher frequencies of genetic aberration in prostate cancers than those found with either method alone or by other approaches. These results indicate the power of simultaneous genetic assays that are closely linked to specific tumor histology. © 1993 Wiley-Liss, Inc.     

A murine tumor progression model for pancreatic cancer recapitulating the genetic alterations of the human disease

This study describes a tumor progression model for ductal pancreatic cancer in mice overexpressing TGF-alpha. Activation of Ras and Erk causes induction of cyclin D1-Cdk4 without increase of cyclin E or PCNA in ductal lesions. Thus, TGF-alpha is able to promote progression throughout G1, but not S phase. Crossbreeding with p53 null mice accelerates tumor development in TGF-alpha transgenic mice dramatically. In tumors developing in these mice, biallelic deletion of Ink4a/Arf or LOH of the Smad4 locus is found suggesting that loci in addition to p53 are involved in antitumor activities. We conclude that these genetic events are critical for pancreatic tumor formation in mice. This model recapitulates pathomorphological features and genetic alterations of the human disease.     

An approach to definition of genetic alterations in prostate cancer.

Growth patterns in prostatic cancer can reduce detectability of genetic alterations. Tumors show histologic grade heterogeneity, multifocality, interdigitation of benign and malignant glands, and varying amounts of stroma. These characteristics introduce sampling errors when one uses traditional methods for genetic analysis that depend on disaggregated cells [metaphase or interphase chromosome studies] or on tissue extracts [Southern blotting or polymerase chain reaction (PCR)] to detect molecular events. To circumvent these problems, we used two approaches to study paraffin-embedded tumors, which permit focused analysis of critical tissue components. Serial 4- to 5-microns sections are applied to slides in groups of three. Every second slide is hematoxylin and eosin stained to visualize areas of carcinoma, dysplasia, hyperplasia, and stroma; tumor-rich areas are circled with ink and used as templates to examine or excise the same areas from adjacent nonstained sections. PCR methods for quantitative and qualitative gene assay are effective in evaluating samples when alteration at a particular locus is suspected. Fluorescence in situ hybridization with chromosome-specific paracentromeric probes for detection of copy number of the relevant chromosome is applied to the adjacent section. Normal chromosome controls for both methods were demonstrated. This protocol enables us to correlate genetic alterations precisely with tumor extent and morphology.     

Detection of genetic alterations in advanced prostate cancer by comparative genomic hybridization

In this study, we examined nine cases of advanced Japanese prostate cancer by comparative genomic hybridization (CGH) to detect chromosomal imbalances across the entire genome and to identify several new regions likely to contain genes important to the development and progression of this disease. These cases had been previously examined for numerical chromosomal aberrations by fluorescence in situ hybridization (FISH). By CGH, the following regions were found to be over-represented (gains), with fluorescence ratio values higher than the threshold: 4p, 6p, 8q, 11q, 12q, 15q, 16p, 17q, 20, and 21 (>4 cases); underrepresentation (losses) involved: 1q, 4q, 5q, 6q, 13q, 14q, and 22 (>4 cases). The shortest regions of overlap (SRO) of gains were noted at 8q24.1 through q24.3, 12q23, and 17q23 through q24 (>5 cases). The SRO of losses were seen at 5q14 through q21, 6q16.1 through q21, 13q21.3 through q22, and 14q21 (>5 cases). Notably, the gain of chromosomes 8 and 12 by CGH was in agreement with the FISH data, suggesting that the gain of chromosomes 8 and 12 may play an important role in prostate carcinogenesis. The genes on the SRO regions were also discussed in relation to oncogenes and bone metastases.     

Cytogenetic alterations in nonmelanoma skin cancer: a review

Since the advent of cytogenetic analysis, knowledge about fundamental aspects of cancer biology has increased, allowing the processes of cancer development and progression to be more fully understood and appreciated. Classical cytogenetic analysis of solid tumors had been considered difficult, but new advances in culturing techniques and the addition of new cytogenetic technologies have enabled a more comprehensive analysis of chromosomal aberrations associated with solid tumors. Our purpose in this review is to discuss the cytogenetic findings on a number of nonmelanoma skin cancers, including squamous- and basal cell carcinomas, keratoacanthoma, squamous cell carcinoma in situ (Bowen's disease), and solar keratosis. Through classical cytogenetic techniques, as well as fluorescence-based techniques such as fluorescence in situ hybridization and comparative genomic hybridization, numerous chromosomal alterations have been identified. These aberrations may aid in further defining the stages and classifications of nonmelanoma skin cancer and also may implicate chromosomal regions involved in progression and metastatic potential. This information, along with the development of newer technologies (including laser capture microdissection and comparative genomic hybridization arrays) that allow for more refined analysis, will continue to increase our knowledge about the role of chromosomal events at all stages of cancer development and progression and, more specifically, about how they are associated with nonmelanoma skin cancer.     

Single-cell sequencing defines genetic heterogeneity in pancreatic cancer precursor lesions

Intraductal papillary mucinous neoplasms (IPMNs) are precursors to pancreatic cancer; however, little is known about genetic heterogeneity in these lesions. The objective of this study was to characterize genetic heterogeneity in IPMNs at the single-cell level. We isolated single cells from fresh tissue from ten IPMNs, followed by whole genome amplification and targeted next-generation sequencing of pancreatic driver genes. We then determined single-cell genotypes using a novel multi-sample mutation calling algorithm. Our analyses revealed that different mutations in the same driver gene frequently occur in the same IPMN. Two IPMNs had multiple mutations in the initiating driver gene KRAS that occurred in unique tumor clones, suggesting the possibility of polyclonal origin or an unidentified initiating event preceding this critical mutation. Multiple mutations in later-occurring driver genes were also common and were frequently localized to unique tumor clones, raising the possibility of convergent evolution of these genetic events in pancreatic tumorigenesis. Single-cell sequencing of IPMNs demonstrated genetic heterogeneity with respect to early and late occurring driver gene mutations, suggesting a more complex pattern of tumor evolution than previously appreciated in these lesions. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Analysis of genetic and epigenetic alterations of the PTEN gene in gastric cancer

The PTEN tumor suppressor gene on 10q23.3, responsible for the Cowden and Bannayan-Zonana syndromes, encodes a dual-specificity phosphatase able to dephosphorylate both tyrosine phosphate and serine/threonine phosphate residues. Mutational inactivation of PTEN has been reported in various malignancies, including endometrial cancers, ovarian cancers, and glioblastomas. In this study, we investigated PTEN gene mutations in 10 gastric cancer cell lines and 58 primary gastric cancers by polymerase chain reaction single strand conformation polymorphism (PCR-SSCP). Hypermethylation of promoter region CpG islands, an alternative mechanism of gene inactivation to coding region mutations, was also evaluated by methylation specific PCR (MSP). Only one (1.7%) of the 58 primary tumors carried a somatic 5-bp deletion in intron 7 of PTEN, which did not alter the mRNA sequence, and no mutations were detected in any of the cell lines. Similar levels of PTEN mRNA expression were observed in all cell lines and primary tumors studied by RT-PCR, and PTEN promoter CpG islands remained unmethylated. Therefore, we conclude that PTEN does not participate in gastric carcinogenesis as a tumor suppressor gene.     

Analysis of genomic DNA alterations and mRNA expression patterns in a panel of human pancreatic cancer cell lines

Genomic alterations influencing the expression and/or activity of tumor suppressors or oncogenes such as KRAS2, CDKN2A, TP53, and DPC4 have been directly implicated in the initiation and progression of human pancreatic adenocarcinoma. In an effort further to systematically characterize the genomic alterations that occur in this disease, we conducted a genome wide analysis of alterations in gene copy number using array-based comparative genomic hybridization (CGH). For this analysis, we utilized a panel of 25 human pancreatic cancer cell lines derived from either primary or metastatic tumors. This panel also included a metastatic progression series of cell lines derived from COLO 357 cells. Array CGH permitted the identification of alterations in the copy number of genes that might participate in the aberrant behavior of pancreatic cancer cells. In addition, the acquisition of invasive and metastatic potential by derivatives of COLO 357 cells was accompanied by additional focal genomic alterations including point mutations and amplification of KRAS2. To complement the array CGH analysis, we also conducted an analysis of mRNA expression patterns in a subset of these cells using cDNA microarrays. By this means, we identified a set of candidate genes, including those regulated by RAS signaling, that may contribute to the process of cancer cell invasion and metastasis. Supplementary material for this article can be found on the Genes, Chromosomes, and Cancer website at http://www.interscience.wiley.com/jpages/1045-2257/suppmat/index.html.     

Heterogeneity of genetic alterations in prostate cancer: evidence of the complex nature of the disease.

Prostate cancer is a complex, multifactorial disease with genetic and environmental factors involved in its etiology. The search for genetic determinants involved in the disease has proven to be challenging, in part because such complex diseases are often not amenable to characterization by linkage analysis and positional cloning as is the case for diseases with simple Mendelian genetic inheritance. Prostate cancer susceptibility loci that have been reported so far include HPC1 (1q24-q25), PCAP (1q42-q43), HPCX (Xq27-q28), CAPB (1p36), HPC20 (20q13), HPC2/ELAC2 (17p11) and 16q23. Prostate cancer aggressiveness loci have also been reported (5q31-q33, 7q32 and 19q12). Further complicating the process is the existence of polymorphisms in several genes associated with prostate cancer including, AR, PSA, SRD5A2, VDR and CYP isoforms. These polymorphisms, however, are not thought to be highly penetrant alleles in families at high risk for prostate cancer. It is clear that prostate cancer etiology involves several genetic loci with no major gene accounting for a large proportion of susceptibility to the disease.     

A pooled analysis of adjuvant chemotherapy for resected colon cancer in elderly patients

BACKGROUND: Adjuvant chemotherapy is standard treatment for patients with resected colon cancer who are at high risk for recurrence, but the efficacy and toxicity of such treatment in patients more than 70 years of age are controversial. METHODS: We performed a pooled analysis, based on the intention to treat, of individual patient data from seven phase 3 randomized trials (involving 3351 patients) in which the effects of postoperative fluorouracil plus leucovorin (five trials) or fluorouracil plus levamisole (two trials) were compared with the effects of surgery alone in patients with stage II or III colon cancer. The patients were grouped into four age categories of equal size, and analyses were repeated with 10-year age ranges (< or =50, 51 to 60, 61 to 70, and >70 years), with the same conclusions. The toxic effects measured in all trials were nausea or vomiting, diarrhea, stomatitis, and leukopenia. Patients in the fluorouracil-plus-leucovorin and fluorouracil-plus-levamisole groups were combined for the efficacy analysis but kept separate for toxicity analyses. RESULTS: Adjuvant treatment had a significant positive effect on both overall survival and time to tumor recurrence (P<0.001 for each, with hazard ratios of death and recurrence of 0.76 [95 percent confidence interval, 0.68 to 0.85] and 0.68 [95 percent confidence interval, 0.60 to 0.76], respectively). The five-year overall survival was 71 percent for those who received adjuvant therapy, as compared with 64 percent for those untreated. No significant interaction was observed between age and the efficacy of treatment. The incidence of toxic effects was not increased among the elderly (age >70 years), except for leukopenia in one study. CONCLUSIONS: Selected elderly patients with colon cancer can receive the same benefit from fluorouracil-based adjuvant therapy as their younger counterparts, without a significant increase in toxic effects.     

Prevalence of CDKN2A mutations in pancreatic cancer patients: implications for genetic counseling

Germline mutations in CDKN2A have been reported in pancreatic cancer families, but genetic counseling for pancreatic cancer risk has been limited by lack of information on CDKN2A mutation carriers outside of selected pancreatic or melanoma kindreds. Lymphocyte DNA from consecutive, unselected white non-Hispanic patients with pancreatic adenocarcinoma was used to sequence CDKN2A. Frequencies of mutations that alter the coding of p16INK4 or p14ARF were quantified overall and in subgroups. Penetrance and likelihood of carrying mutations by family history were estimated. Among 1537 cases, 9 (0.6%) carried germline mutations in CDKN2A, including three previously unreported mutations. CDKN2A mutation carriers were more likely to have a family history of pancreatic cancer (P=0.003) or melanoma (P=0.03), and a personal history of melanoma (P=0.01). Among cases who reported having a first-degree relative with pancreatic cancer or melanoma, the carrier proportions were 3.3 and 5.3%, respectively. Penetrance for mutation carriers by age 80 was calculated to be 58% for pancreatic cancer (95% confidence interval (CI) 8–86%), and 39% for melanoma (95% CI 0–80). Among cases who ever smoked cigarettes, the risk for pancreatic cancer was higher for carriers compared with non-carriers (HR 25.8, P=2.1 × 10⁻¹³), but among nonsmokers, this comparison did not reach statistical significance. Germline mutations in CDKN2A among unselected pancreatic cancer patients are uncommon, although notably penetrant, especially among smokers. Carriers of germline mutations of CDKN2A should be counseled to avoid tobacco use to decrease risk of pancreatic cancer in addition to taking measures to decrease melanoma risk.