Cristina Oliani

Microsatellite Instability and Colorectal Cancer Prognosis

Purpose: Many studies have evaluated the role of high levels of microsatellite instability (MSI) as a prognostic marker and predictor of the response to chemotherapy in colorectal cancer (CRC); however, the results are not conclusive. The aim of this study was to analyze the prognostic significance of high levels of MSI (MSI-H) in CRC patients in relation to fluorouracil-based chemotherapy. Experimental Design: In three different institutions, 1,263 patients with CRC were tested for the presence of MSI, and CRC-specific survival was then analyzed in relation to MSI status, chemotherapy, and other clinical and pathologic variables. Results: Two hundred and fifty-six tumors were MSI-H (20.3%): these were more frequently at a less advanced stage, right-sided, poorly differentiated, with mucinous phenotype, and expansive growth pattern than microsatellite stable carcinomas. Univariate and multivariate analyses of 5-year–specific survival revealed stage, tumor location, grade of differentiation, MSI, gender, and age as significant prognostic factors. The prognostic advantage of MSI tumors was particularly evident in stages II and III in which chemotherapy did not significantly affect the survival of MSI-H patients. Finally, we analyzed survival in MSI-H patients in relation to the presence of mismatch repair gene mutations. MSI-H patients with hereditary non–polyposis colorectal cancer showed a better prognosis as compared with sporadic MSI-H; however, in multivariate analysis, this difference disappeared. Conclusions: The type of genomic instability could influence the prognosis of CRC, in particular in stages II and III. Fluorouracil-based chemotherapy does not seem to improve survival among MSI-H patients. The survival benefit for patients with hereditary non–polyposis colorectal cancer is mainly determined by younger age and less advanced stage as compared with sporadic MSI-H counterpart.

Molecular characterization of the spectrum of genomic deletions in the mismatch repair genes MSH2, MLH1, MSH6, and PMS2 responsible for hereditary nonpolyposis colorectal cancer (HNPCC).

A systematic search by Southern blot analysis in a cohort of 439 hereditary nonpolyposis colorectal cancer (HNPCC) families for genomic rearrangements in the main mismatch repair (MMR) genes, namely, MSH2, MLH1, MSH6, and PMS2, identified 48 genomic rearrangements causative of this inherited predisposition to colorectal cancer in 68 unrelated kindreds. Twenty‐nine of the 48 rearrangements were found in MSH2, 13 in MLH1, 2 in MSH6, and 4 in PMS2. The vast majority were deletions, although one previously described large inversion, an intronic insertion, and a more complex rearrangement also were found. Twenty‐four deletion breakpoints have been identified and sequenced in order to determine the underlying recombination mechanisms. Most fall within repetitive sequences, mainly Alu repeats, in agreement with the differential distribution of deletions between the MSH2 and MLH1 genes: the higher number and density of Alu repeats in MSH2 corresponded with a higher incidence of genomic rearrangement at this disease locus when compared with other MMR genes. Long interspersed nuclear element (LINE) repeats, relatively abundant in, for example, MLH1, did not seem to contribute to the genesis of the deletions, presumably because of their older evolutionary age and divergence among individual repeat units when compared with short interspersed nuclear element (SINE) repeats, including Alu repeats. Moreover, Southern blot analysis of the introns and the genomic regions flanking the MMR genes allowed us to detect 6 novel genomic rearrangements that left the coding region of the disease‐causing gene intact. These rearrangements comprised 4 deletions upstream of the coding region of MSH2 (3 cases) and MSH6 (1 case), a 2‐kb insertion in intron 7 of PMS2, and a small (459‐bp) deletion in intron 13 of MLH1. The characterization of these genomic rearrangements underlines the importance of genomic deletions in the etiology of HNPCC and will facilitate the development of PCR‐based tests for their detection in diagnostic laboratories.

The reliability of immunohistochemistry as a prescreening method for the diagnosis of hereditary nonpolyposis colorectal cancer (HNPCC) - Results of an international collaborative study

Hereditary nonpolyposis colorectal cancer syndrome (HNPCC) is an autosomal dominant condition accounting for 2–5% of all colorectal carcinomas as well as a small subset of endometrial, upper urinary tract and other gastrointestinal cancers. An assay to detect the underlying defect in HNPCC, inactivation of a DNA mismatch repair enzyme, would be useful in identifying HNPCC probands. Monoclonal antibodies against hMLH1 and hMSH2, two DNA mismatch repair proteins which account for most HNPCC cancers, are commercially available. This study sought to investigate the potential utility of these antibodies in determining the expression status of these proteins in paraffin-embedded formalin-fixed tissue and to identify key technical protocol components associated with successful staining. A set of 20 colorectal carcinoma cases of known hMLH1 and hMSH2 mutation and expression status underwent immunoperoxidase staining at multiple institutions, each of which used their own technical protocol. Staining for hMSH2 was successful in most laboratories while staining for hMLH1 proved problematic in multiple labs. However, a significant minority of laboratories demonstrated excellent results including high discriminatory power with both monoclonal antibodies. These laboratories appropriately identified hMLH1 or hMSH2 inactivation with high sensitivity and specificity. The key protocol point associated with successful staining was an antigen retrieval step involving heat treatment and either EDTA or citrate buffer. This study demonstrates the potential utility of immunohistochemistry in detecting HNPCC probands and identifies key technical components for successful staining.

Integrated analysis of unclassified variants in mismatch repair genes

Purpose: Lynch syndrome is a genetic disease that predisposes to colorectal tumors, caused by mutation in mismatch repair genes. The use of genetic tests to identify mutation carriers does not always give perfectly clear results, as happens when an unclassified variant is found. This study aimed to define the pathogenic role of 35 variants present in MSH2, MLH1, MSH6, and PMS2 genes identified in our 15-year case study.Methods: We collected clinical and molecular data of all carriers, and then we analyzed the variants pathogenic role with web tools and molecular analyses. Using a Bayesian approach, we derived a posterior probability of pathogenicity and classified each variant according to a standardized five-class system.Results: The MSH2 p.Pro349Arg, p.Met688Arg, the MLH1 p.Gly67Arg, p.Thr82Ala, p.Lys618Ala, the MSH6 p.Ala1236Pro, and the PMS2 p.Arg20Gln were classified as pathogenic, and the MSH2 p.Cys697Arg and the PMS2 p.Ser46Ile were classified as likely pathogenic. Seven variants were likely nonpathogenic, 3 were nonpathogenic, and 16 remained uncertain.Conclusion: Quantitative assessment of several parameters and their integration in a multifactorial likelihood model is the method of choice for classifying the variants. As such classifications can be associated with surveillance and testing recommendations, the results and the method developed in our study can be useful for helping laboratory geneticists in evaluation of genetic tests and clinicians in the management of carriers.

Spectrum of genetic alterations in Muir‐Torre syndrome is the same as in HNPCC

Muir-Torre Syndrome (MTS) is a cancer predisposing syndrome in which the development of cutaneous lesions are associated to tumors belonging to the spectrum of HNPCC (colorectum, endometrium, stomach, ovary, biliary tree). The cutaneous lesions include sebaceous adenomas, epitheliomas, and carcinomas as well as basaliomas. The initial and exclusive identification ofMSH2mutations [Kolodner et al., 1994] led to the hypothesis that the specific MTS phenotype was due to the involvement of this gene [Kruse et al., 1996]. The subsequent finding of a germline MLH1 point mutation inaMTS family byBapat et al. [1996] clarified that other mismatch repair genes responsible for HNPCC, may underly MTS. To date, the spectrum of germline MSH2 and MLH1 mutations in MTS families includes missense, nonsense, or frameshift mutations [Kolodner et al., 1994; Bapat et al., 1996; Suspiro et al., 1998; Godard et al., 1999]. Here we report the firstMTS family harboring a large deletion within the MSH2 gene. This finding confirms that the spectrum of genetic alterations in MTS is similar to that of HNPCC. The family is characterized by three affected individuals within two generations (Fig. 1). In particular, the father had two metachronous colon cancers starting at 53 years, a daughter who had a colon and ovarian cancer starting at age 42, a son affected by an adenoma with a focus of carcinoma at age 47. All three affected members also presented with cutaneous lesions characteristic of MTS. Two additional sons and a daughter were unaffected. All colon cancers were tested for the presence of microsatellite instability (MSI) using BAT25 and Fig. 1. VR1 pedigree.

A genetic model for determining MSH2 and MLH1 carrier probabilities based on family history and tumor microsatellite instability

Mutation‐predicting models can be useful when deciding on the genetic testing of individuals at risk and in determining the cost effectiveness of screening strategies at the population level. The aim of this study was to evaluate the performance of a newly developed genetic model that incorporates tumor microsatellite instability (MSI) information, called the AIFEG model, and in predicting the presence of mutations in MSH2 and MLH1 in probands with suspected hereditary non‐polyposis colorectal cancer. The AIFEG model is based on published estimates of mutation frequencies and cancer penetrances in carriers and non‐carriers and employs the program MLINK of the FASTLINK package to calculate the probands carrier probability. Model performance is evaluated in a series of 219 families screened for mutations in both MSH2 and MLH1, in which 68 disease‐causing mutations were identified. Predictions are first obtained using family history only and then converted into posterior probabilities using information on MSI. This improves predictions substantially. Using a probability threshold of 10% for mutation analysis, the AIFEG model applied to our series has 100% sensitivity and 71% specificity.

Carcinoid crisis induced by receptor radionuclide therapy with 90Y-DOTATOC in a case of liver metastases from bronchial neuroendocrine tumor (atypical carcinoid)

SS receptors are overexpressed in many tumors, mainly of neuroendocrine origin, thus enabling the treatment with SS analogs. The clinical experience of receptor radionuclide therapy with the new analog [90Y-DOTA0-Tyr3]-octreotide [90Y-DOTATOC] has been developed over the last decade and is gaining a pivotal role in the therapeutic workout of these tumors. It is well known that some procedures performed in diagnostic and therapeutic management of endocrine tumors, such as agobiopsy and hepatic chemoembolization, can be associated with the occurrence of symptoms related to the release of vasoactive amines and/or hormonal peptides from tumor cell lysis. This is the first report of a severe carcinoid crisis developed after receptor radionuclide therapy with 90Y-DOTATOC administered in a patient affected by liver metastases from bronchial neuroendocrine tumor (atypical carcinoid). Despite protection with H1 receptor antagonists, octreotide and corticosteroids, few days after the therapy the patient complained of persistent flushing of the face and upper trunk, severe labial and periocular oedema, diarrhoea and loss of appetite. These symptoms increased and required new hospitalisation. The patient received iv infusion of octreotide associated with H1 and H2 receptor antagonists and corticosteroid therapy, which induced symptom remission within few days. The case here reported confirms that radionuclide therapy is highly effective in determining early rupture of metastatic tissue and also suggests that pre-medication should be implemented before the radiopeptide administration associated with a close monitoring of the patient in the following days.

Performance of BOADICEA and BRCAPRO genetic models and of empirical criteria based on cancer family history for predicting BRCA mutation carrier probabilities: A retrospective study in a sample of Italian cancer genetics clinics

PURPOSE To evaluate in current practice the performance of BOADICEA and BRCAPRO risk models and empirical criteria based on cancer family history for the selection of individuals for BRCA genetic testing. PATIENTS AND METHODS The probability of BRCA mutation according to the three tools was retrospectively estimated in 918 index cases consecutively undergone BRCA testing at 15 Italian cancer genetics clinics between 2006 and 2008. RESULTS 179 of 918 cases (19.5%) carried BRCA mutations. With the strict use of the criteria based on cancer family history 173 BRCA (21.9%) mutations would have been detected in 789 individuals. At the commonly used 10% threshold of BRCA mutation carrier probability, the genetic models showed a similar performance [PPV (38% and 37%), sensitivity (76% and 77%) and specificity (70% and 69%)]. Their strict use would have avoided around 60% of the tests but would have missed approximately 1 every 4 carriers. CONCLUSION Our data highlight the complexity of BRCA testing referral in routine practice and question the strict use of genetic models for BRCA risk assessment.

Multidisciplinary approach including receptor radionuclide therapy with 90Y-DOTATOC ([90Y-DOTA0, Tyr3]-octreotide) and 177Lu-DOTATATE ([177Lu-DOTA0, Tyr3]-octreotate) in ectopic cushing syndrome from a metastatic gastrinoma: a promising proposal.

OBJECTIVE To present a case of a young woman with Cushing syndrome caused by ectopic production of adrenocorticotropic hormone from a metastatic pancreatic gastrin-secreting endocrine carcinoma, who had a good response to combination peptide receptor radionuclide therapy. METHODS We review the history, physical examination, laboratory investigations, and radiographic findings in this unusual patient. Moreover, the multimodal interventions are described and discussed. RESULTS In a 38-year-old woman with typical signs of cortisol excess, laboratory studies revealed diabetes mellitus, hypokalemia, and high levels of adrenocorticotropic hormone, plasma cortisol, and urinary cortisol. Abdominal computed tomography showed a 4-cm pancreatic mass and multiple metastatic lesions in the liver, and ectopic Cushing syndrome was diagnosed. Treatment consisted of surgical debulking of the tumor, ketoconazole, somatostatin analogues, chemoembolization of the liver metastatic lesions, and peptide receptor radionuclide therapy with the radiolabeled somatostatin analogues 90Y-DOTATOC ([90Y-DOTA0, Tyr3]-octreotide) and 177Lu-DOTATATE ([177Lu-DOTA0, Tyr3]-octreotate). The 5 1/2-year follow-up showed positive results, which included complete regression of all clinical and hormonal evidence of the tumor and substantial decrease in the size and number of hepatic metastatic lesions. The patient achieved and still maintains an optimal quality of life. CONCLUSION To the best of our knowledge, this is the first report of a multidisciplinary approach including peptide receptor radionuclide therapy with 90Y-DOTATOC and 177Lu-DOTATATE, which proved to be effective in improving clinical outcome in a case of metastatic endocrine carcinoma of the pancreas in conjunction with ectopic Cushing syndrome. In this unusual case, the patient has one of the longest durations of survival in this setting described in the literature.

MUTYH c.933+3A > C, associated with a severely impaired gene expression, is the first Italian founder mutation in MUTYH-Associated Polyposis

MUTYH variants are differently distributed in geographical areas of the world. In MUTYH‐associated polyposis (MAP) patients from North‐Eastern Italy, c.933+3A>C (IVS10+3A>C), a transversion causing an aberrant splicing process, accounts for nearly 1/5 of all mutations. The aim of this study was to verify whether its high frequency in North‐Eastern Italy is due to a founder effect and to clarify its impact on MUTYH transcripts and protein. Haplotype analysis and age estimate performed on members of eleven Italian MAP families and cancer‐free controls provided evidence that c.933+3A>C is a founder mutation originated about 83 generations ago. In addition, the Italian haplotype associated with the c.933+3A>C was also found in German families segregating the same mutation, indicating it had a common origin in Western Europe. Altogether c.933+3A>C and the two common Caucasian mutations p.Tyr179Cys and p.Gly396Asp represent about 60% of MUTYH alterations in MAP patients from North‐Eastern Italy, suggesting the opportunity to perform targeted molecular screening for these variants in the diagnostic setting. Expression analyses performed on lymphoblastoid cell lines supported the notion that MUTYH c.933+3A>C alters splicing causing the synthesis of a non functional protein. However, some primary transcripts escape aberrant splicing, producing traces of full‐length transcript and wild‐type protein in a homozygote; this is in agreement with clinical findings that suggest a relatively mild phenotypic effect for this mutation. Overall, these data, that demonstrate a founder effect and further elucidate the splicing alterations caused by the MUTYH c.933+3A>C mutation, have important implications for genetic counseling and molecular diagnosis of MAP.