Alison J. Whelan

DICER1 Mutations in Familial Pleuropulmonary Blastoma

A rare form of lung cancer in children is associated with mutational disruption of an enzyme that generates small noncoding RNAs. Pleuropulmonary blastoma (PPB) is a rare pediatric lung tumor that is often part of an inherited cancer syndrome. PPBs consist of mesenchymal cells that are susceptible to malignant transformation and cysts lined by epithelial cells. In a subset of patients, overgrowth of the cysts by mesenchymal cells leads to sarcoma formation. Here, we show that 11 multiplex PPB families harbor heterozygous germline mutations in DICER1, a gene encoding an endoribonuclease critical to the generation of small noncoding regulatory RNAs. Expression of DICER1 protein was undetectable in the epithelial component of PPB tumors but was retained in the malignant mesenchyme (sarcoma). We hypothesize that loss of DICER1 in the epithelium of the developing lung alters the regulation of diffusible factors that promote mesenchymal proliferation.

Penetrance and Expressivity of MSH6 Germline Mutations in Seven Kindreds Not Ascertained by Family History

Hereditary nonpolyposis colorectal cancer (HNPCC) is caused by inherited mutations in DNA mismatch-repair genes, most commonly MLH1 or MSH2. The role MSH6 plays in inherited cancer susceptibility is less well defined. The aim of this study was to investigate the penetrance and expressivity of MSH6 mutations in kindreds ascertained through endometrial cancer probands unselected for family history. Detailed pedigrees were constructed for six MSH6 mutation carriers. All reported cancers and precancers were confirmed, and tissues were obtained when available. Tumors were analyzed for microsatellite instability (MSI) and for expression of MSH2, MLH1, and MSH6. MSH6 mutation status was determined for 59 family members. Of these 59 individuals, 19 (32%) had confirmed cancers and precancers. There was an excess of mutation carriers among the 19 affected family members (11 [58%] of 19) compared with those among the 40 unaffecteds (8 [20%] of 40, P=.0065, odds ratio = 5.5, 95% CI = 1.66-18.19). In four of the seven tumors analyzed from mutation carriers other than the probands, MSI and/or MMR protein expression was consistent with the involvement of MSH6. Overall estimated penetrance of the MHS6 mutations was 57.7%. Of the tumors in mutation carriers, 78% were part of the extended HNPCC spectrum. This study demonstrates that MSH6 germline mutations are, indeed, associated with increased cancer risk and that the penetrance of mutations may be higher than appreciated elsewhere. A combination of MSI and immunohistochemistry analyses may be helpful in screening for MSH6 mutation carriers.

Mutations in the GGCX and ABCC6 Genes in a Family with Pseudoxanthoma Elasticum-Like Phenotypes

A characteristic feature of classic pseudoxanthoma elasticum (PXE), an autosomal recessive disorder caused by mutations in the ABCC6 gene, is aberrant mineralization of connective tissues, particularly the elastic fibers. Here, we report a family with PXE-like cutaneous features in association with multiple coagulation factor deficiency, an autosomal recessive disorder associated with GGCX mutations. The proband and her sister, both with severe skin findings with extensive mineralization, were compound heterozygotes for missense mutations in the GGCX gene, which were shown to result in reduced gamma-glutamyl carboxylase activity and in undercarboxylation of matrix gla protein. The probands mother and aunt, also manifesting with PXE-like skin changes, were heterozygous carriers of a missense mutation (p.V255M) in GGCX and a null mutation (p.R1141X) in the ABCC6 gene, suggesting digenic nature of their skin findings. Thus, reduced gamma-glutamyl carboxylase activity in individuals either compound heterozygous for a missense mutation in GGCX or with haploinsufficiency in GGCX in combination with heterozygosity for ABCC6 gene expression results in aberrant mineralization of skin leading to PXE-like phenotype. These findings expand the molecular basis of PXE-like phenotypes, and suggest a role for multiple genetic factors in pathologic tissue mineralization in general.

Mutations in MLH1 are more frequent than in MSH2 in sporadic colorectal cancers with microsatellite instability

The microsatellite instability that is a feature of tumors in patients with hereditary nonpolyposis colorectal cancer (HNPCC) is a consequence of defective DNA mismatch repair. Mutations in the DNA mismatch repair genes MSH2 and MLH1 may account for up to 90% of HNPCC kindreds. Microsatellite instability is also seen in 10–16% of sporadic colorectal cancers. A limited number of MSH2 and MLH1 mutations have been described for sporadic colorectal cancers. In this study, we screened 12 primary sporadic colorectal cancers with microsatellite instability for mutations in MSH2 and MLH1 by using reverse transcription‐polymerase chain reaction (RT‐PCR) and single‐strand‐conformation‐variant (SSCV) analysis. Eight mutations were identified in six tumors. One mutation in MLH1 was found to be present in the patients germline DNA. Four tumors had somatic mutations in MLH1, and, in two of these tumors, two different mutations were identified. A single tumor had a somatic MSH2 mutation. Our observations suggest that MLH1 is mutated more frequently than MSH2 in sporadic colorectal cancers with microsatellite instability. Genes Chromosom. Cancer 18:42–49, 1997.

MSI in endometrial carcinoma: Absence of MLH1 promoter methylation is associated with increased familial risk for cancers

Loss of DNA mismatch repair occurs in a variety of malignancies and is associated with genome‐wide instability of microsatellite repeats, a molecular phenotype referred to as microsatellite instability (MSI). MSI is a consistent feature of colorectal and endometrial tumors from patients with hereditary non‐polyposis colorectal cancer (HNPCC). Sporadic colorectal and endometrial cancers that exhibit MSI frequently have methylation of the MLH1 promoter. We undertook a detailed family and medical history study to compare family cancer risk for women with MSI‐positive and ‐negative endometrial cancers. The MLH1 promoter methylation status was determined for all cancers. Family histories were developed for 80 probands (40 with MSI‐positive and 40 with MSI‐negative tumors). The numbers of reported cancers in first‐ and second‐degree relatives of the 2 groups were similar. There was a modest increase in familial cancer clustering for MSI‐positive probands. When MSI‐positive tumors were subclassified according to MLH1 promoter methylation, a clear association between methylation status and familial cancer risk was evident. Women with MSI‐positive endometrial cancers in which the MLH1 promoter was unmethylated had a 7‐fold relative risk (RR) of demonstrating familial clustering of cancers [RR 7.07 (95% confidence interval 2.29–21.81)]. The women with MSI‐positive, MLH1‐unmethylated tumors were significantly younger than the rest of the study population (56.1 years vs. 65.4, p ≤ 0.01). Age of onset and tumor MSI not associated with MLH1 promoter methylation may point to women with a genetic susceptibility to malignancies.

The changing paradigm of contemporary U.S. allopathic medical school graduates' career paths: analysis of the 1997-2004 national AAMC Graduation Questionnaire database.

Purpose During the last 15 years, the proportion of U.S. allopathic medical graduates planning to pursue alternative careers (other than full-time clinical practice) has been increasing. The authors sought to identify factors associated with contemporary medical graduates’ career-setting plans. Method The authors obtained anonymous data from the 108,408 U.S. allopathic medical graduates who completed the 1997–2004 national Association of American Medical Colleges Graduation Questionnaire (GQ). Using multinomial logistic regression, responses to eight GQ items regarding graduates’ demographics, medical school characteristics, and specialty choice were tested in association with three career-setting plans (full-time university faculty; other, including government agencies, non-university-based research, or medical or health care administration; or undecided) compared with full-time (nonacademic) clinical practice. Results The sample included 94,101 (86.8% of 108,408) GQ respondents with complete data. From 1997 to 2004, the proportions of graduates planning full-time clinical practice careers decreased from 51.3% to 46.5%; the proportions selecting primary care and obstetrics–gynecology specialties also decreased. Graduates reporting Hispanic race/ethnicity or no response to race/ethnicity, lower debt, dual advanced degrees at graduation, and psychiatric-specialty choice were consistently more likely to plan to pursue alternative careers. Graduates selecting an obstetrics–gynecology specialty/ subspecialty were consistently less likely to plan to pursue alternative careers. Being female, Asian/Pacific Islander, Black or Native American/Alaskan, and selecting non-primary-care specialties were variably associated with alternative career plans. Conclusions As the medical student population becomes more demographically diverse, as graduates increasingly select non-primary-care specialties, and as dual-degree-program graduates and alternative career opportunities for physicians expand, the proportion of U.S. graduates planning full-time clinical practice careers likely will continue to decline.

A practical approach to familial and hereditary colorectal cancer

Recent genetic research has isolated the primary genetic defect underlying many of the hereditary colorectal cancer syndromes. Obtaining a detailed family history is the first step in identifying individuals at increased risk of developing colorectal cancer. Once identified, individuals and their families may benefit from earlier, more intensified surveillance, prophylactic surgery, cancer risk assessment and education, and genetic testing. Clinicians, especially those with many patients with colorectal cancer in their practice, must be able to address the complex issues associated with the familial and hereditary colorectal cancer syndromes. A well-integrated partnership among colorectal surgeons, gastroenterologists, oncologists, and medical geneticists is necessary to address these complex issues and provide comprehensive medical care.

What predicts USMLE Step 3 performance

Background Academic and other student-specific variables associated with United States Medical Licensing Examination (USMLE) Step 3 performance have not been fully defined. Method We analyzed Step 3 scores in association with medical school academic-performance measures, gender, residency specialty, and first postgraduate year (PGY-l) of training program-director performance evaluations. Results There were significant first-order associations between Step 3 scores and each of USMLE Step 1 and Step 2 scores, third-year clerkships’ grade point average (GPA), Alpha Omega Alpha election, Medical Scientist Training Program graduation, broad-based specialty residency training, and PGY-l performance evaluation score. In a multiple linear regression model accounting for over 50% of the total variance in Step 3 scores, Step 2 scores, broad-based-specialty residency training, and GPA independently predicted Step 3 scores. Conclusions Individualized Step 3 scores provide medical schools with additional means to externally validate their educational programs and to enhance the scope of outcomes assessments for their graduates.

Qualitative Evaluation of Medical Information Processing Needs of 60 Women Choosing Ovarian Cancer Surveillance or Prophylactic Oophorectomy

Thirty women who had prophylactic oophorectomy (PO) and thirty women undergoing ovarian cancer surveillance (OCS) completed a one-time in-depth telephone interview exploring information gathering and decision-making processes. There were close similarities between groups, including age, race, marital status, education, menopausal status, number undergoing genetic testing for BRCA mutations, and number of prophylactic mastectomies. The majority of participants indicated overall satisfaction with their final decision. However, many described the information gathering process as frustrating and anxiety provoking. Participants in both groups expressed a need to process medical information within the context of individual psychosocial needs and personal perceptions and experiences. There were recurrent themes with regard to informational and psychosocial needs and personal perceptions and experiences that impacted decision-making process for these women. The present paper is a companion paper to Swisher et al. (J Repr Med 2001, 46:87–94) with the focus of this paper to illustrate the medical informational processing needs identified by this group of women.

Epitope-positive truncating MLH1 mutation and loss of PMS2: implications for IHC-directed genetic testing for lynch syndrome

We assessed mismatch repair by immunohistochemistry (IHC) and microsatellite instability (MSI) analysis in an early onset endometrial cancer and a sister’s colon cancer. We demonstrated high-level MSI and normal expression for MLH1, MSH2 and MSH6. PMS2 failed to stain in both tumors, strongly implicating a PMS2 defect. This family did not meet clinical criteria for Lynch syndrome. However, early onset endometrial cancers in the proband and her sister, a metachronous colorectal cancer in the sister as well as MSI in endometrial and colonic tumors suggested a heritable mismatch repair defect. PCR-based direct exonic sequencing and multiplex ligation-dependent probe amplification (MLPA) were undertaken to search for PMS2 mutations in the germline DNA from the proband and her sister. No mutation was identified in the PMS2 gene. However, PMS2 exons 3, 4, 13, 14, 15 were not evaluated by MLPA and as such, rearrangements involving those exons cannot be excluded. Clinical testing for MLH1 and MSH2 mutation revealed a germline deletion of MLH1 exons 14 and 15. This MLH1 germline deletion leads to an immunodetectable stable C-terminal truncated MLH1 protein which based on the IHC staining must abrogate PMS2 stabilization. To the best of our knowledge, loss of PMS2 in MLH1 truncating mutation carriers that express MLH1 in their tumors has not been previously reported. This family points to a potential limitation of IHC-directed gene testing for suspected Lynch syndrome and the need to consider comprehensive MLH1 testing for individuals whose tumors lack PMS2 but for whom PMS2 mutations are not identified.