Isolated Loss of PMS2 Expressionin Colorectal Cancers: Frequency, Patient Age, and Familial Aggregation Sharlene Gill, 1 Noralane M. Lindor, 2 LawrenceJ. Burgart, 3 Regenia Smalley, 3 Olga Leontovich, 3 AmyJ.French, 3 RichardM.Goldberg, 5 DanielJ.Sargent, 4 JeremyR.Jass, 6 JohnL.Hopper, 7 Mark A. Jenkins, 7 JoanneYoung, 8 Melissa A. Barker, 8 Michael D.Walsh, 8 Andrew R. Ruszkiewicz, 9 and Stephen N.Thibodeau 3 Abstract Purpose: Mostcolorectalcancersthathavehighlevelsofmicrosatelliteinstability(MSI-H)show lossofimmunohistochemicalexpressionofproteinsthatparticipateintheDNAmismatchrepair process, most ofteninvolving MLH1and MSH2. Less commonly, a third DNA mismatch repair protein, MSH6, may alsobe lost as the primary event. Rarely, tumors with MSI-H show normal expressionofthesethreeproteins.ThegeneticdeficiencyleadingtotheMSI-Hphenotypeinsuch casesisunknown.PMS2isanothermemberoftheDNAmismatchrepaircomplex.Itsexpression is generally lostin tumors with MLH1loss of expression. Rarely, there is selective loss of PMS2 expression.We sought to describe the frequency and clinical correlates of selective loss of expressionofPMS2withtheMSI-Htumorphenotype. Experimental Design: Two thousand sevenhundrednineteencolorectalcancers fromboth clinic- and research-based ascertainment were studied.Tumor MSItesting andimmuno- histochemistry for MLH1, MSH2, MSH6, and PMS2 were conducted. Medical records were abstractedforageatdiagnosis,gender,colorectalcancersite,andfamilyhistory. Results: Five hundred thirty-five of the 2,719 tumors were MSI-H. Of these, 93% showed loss of expressionof MLH1, MSH2, and/or MSH6.Thirty-eight showednormal expression for these proteins. PMS2 immunohistochemical staining was successful in 32 of 38 of these tumors. Of the 32, 23 showed selective loss of expression of PMS2.This was associated with young age of diagnosis and right-sided location but not with a striking family history of cancer. Conclusions: Overall,97%oftheMSI-Htumorsshowedlossofexpressionforoneormoreof thesefourmismatchrepairproteins.SelectivelossofexpressionofPMS2waspresentin72% ofcasesinwhichcolorectalcancershadanMSI-Hphenotypebutnoalterationofexpressionof MLH1, MSH2, and MSH6.The underlying mechanisminvolved cannot be determined from this study but couldinvolve point mutations in other DNA mismatch repair genes with retention of immunohistochemicalexpression,somaticinactivationof PMS2 ,orgermlinemutationof PMS2 . Tumor DNA microsatellite instability (MSI) is a consequence of defects in DNA mismatch repair. A high level of micro- satellite instability (MSI-H) is recognized in a subset of patients diagnosed with Hereditary Nonpolyposis Colorectal Cancer (HNPCC) by pedigree, and in 10% to 15% of all colorectal cancers in most unselected series (1–3). Both somatic and germ line mutations have been identified in several putative genes from the mutS (MSH2, MSH3 , and MSH6 ) and mutL (MLH1, MLH3, PMS1 , and PMS2 ) gene families in colon cancer with defective mismatch repair (4 – 7). Human Cancer Biology Authors’Affiliations: 1 British Columbia CancerAgency,Vancouver, British Columbia,Canada;Departmentsof 2 MedicalGenetics, 3 LaboratoryMedicineand Pathology, and 4 Health Sciences Research, Mayo Clinic College of Medicine, Rochester,Minnesota; 5 Universityof NorthCarolinaat Chapel Hill, Chapel Hill, NorthCarolina; 6 DepartmentofPathology,McGillUniversity,Montreal,Quebec, Canada; 7 CentreforGeneticEpidemiology,UniversityofMelbourne,Melbourne, Victoria, Australia; 8 Queensland Institute of Medical Research, Brisbane, Queensland,Australia;and 9 InstituteofMedicalandVeterinaryScience,Adelaide, South Australia, Australia Received3/24/05;revised5/16/05;accepted6/20/05. Grant support: National Cancer Institute, NIHunder RFA #CA-95-011, and through cooperative agreements with the members of the Colon Cancer Family Registryandprincipalinvestigators.The NCCTG study was supportedinpart by NationalCancerInstitutegrantsCA25224andCA60117. Collaborating centers include theAustralasia Colorectal Cancer Family Registry (UO1 CA097735), the USCFamilial Colorectal Neoplasia Collaborative Group (UO1 CA074799), Mayo Clinic Cooperative Family Registry for Colon Cancer Studies (UO1CA074800),OntarioRegistry forStudiesofFamilialColorectalCancer(UO1 CA074783), Seattle Colorectal Cancer Family Registry (UO1CA074794), University of Hawaii Colorectal Cancer Family Registry (UO1CA074806), and UniversityofCalifornia,IrvineInformaticsCenter(UO1CA078296). Thecontentofthismanuscriptdoesnotnecessarilyreflecttheviewsorpoliciesofthe NationalCancerInstituteoranyofthecollaboratingcentersintheCooperativeFamily Registries,nordoesmentionoftradenames,commercialproducts,ororganizations implyendorsementbytheUSGovernmentortheCooperativeFamilyRegistry. Thecostsofpublicationofthisarticleweredefrayedinpartbythepaymentofpage charges.Thisarticlemustthereforebeherebymarked advertisement inaccordance with18U.S.C.Section1734solelytoindicatethisfact. Requests for reprints: Stephen N.Thibodeau, DivisionofLaboratory Genetics, Mayo Clinic College of Medicine, 920 Hilton Building, 200 First Street Southwest, Rochester,MN55905.Phone: 507-284-4696;Fax: 507-284-0670;E-mail: sthibodeau@mayo.edu. F 2005AmericanAssociationforCancerResearch. doi:10.1158/1078-0432.CCR-05-0661 www.aacrjournals.org ClinCancerRes2005;11(18)September15,2005 6466 Downloaded from http://aacrjournals.org/clincancerres/article-pdf/11/18/6466/1960399/6466-6471.pdf by guest on 14 June 2022