Pediatr Blood Cancer 2012;58:1006–1007 LETTER TO THE EDITOR Mutations of PTCH1, MLL2, and MLL3 Are Not Frequent Events in Hepatoblastoma To the Editor: Hepatoblastoma (HB), the most common ma- lignant liver tumor in children, is a biologically and clinically heterogeneous embryonal malignancy. Dysregulation of core de- velopmental pathways, including Wnt/wingless, is thought to be critical to HB development [1–5]. A recent genomic analysis of medulloblastoma, another embryonal tumor of childhood, revealed frequent mutation of the CTNNB1 (Wnt/wingless path- way), PTCH1 (Sonic Hedgehog pathway), and MLL2/MLL3 (chromatin remodeling) genes [6], prompting us to evaluate these genes for somatic mutations in a cohort of histopathologically confirmed HB samples in order to assess whether these genes are also commonly mutated in HB. DNA and RNA were extracted from a cohort of 18 clinically annotated HB samples and patient-matched normal tissues as previously described [1]. The histopathologic diagnosis of HB was confirmed for each case and basic clinical data obtained for each patient (Table I). Family or prior medical history was signif- icant for three patients: an 11-year-old male with familial adeno- matous polyposis (FAP) and Gilbert’s syndrome, a 6-year-old male with a sibling who died of hepatocellular carcinoma (HCC) at 10 years of age, and a 15 month old male with Beckwith–Wiedemann syn- drome (BWS). Polymerase chain reaction primers for MLL2, MLL3, PTCH1, and CTNNB1 were used to amplify and bidirectionally Sanger sequence all coding exons of these genes using DNA extracted from HB tumor samples and matched normal samples [6]. The resulting data were analyzed for somatic mutations using Muta- tion Surveyor version 3.97 (SoftGenetics LLC, State College, PA). In order to identify larger deletions of CTNNB1, cDNA- based sequencing of the CTNNB1 gene was also performed [1]. In tumors where more than one CTNNB1 mutation was found, RT-PCR products were subjected to TOPO cloning (Invitrogen, Carlsbad, CA) and sequencing in order to determine whether the mutations were on the same or different chromosomes. Our data confirm the previously reported high frequency of somatic alterations targeting the Wnt/Wingless pathway gene CTNNB1 in HB, with point mutations or deletions identified in 12 of 18 tumors analyzed (67%) [1–4]. All CTNNB1 point muta- tions identified had previously been reported in HB except for p.Tyr30Ser. Somatic CTNNB1 alterations were not detected in the three tumors obtained from patients with a known inherited cancer predisposition syndrome (FAP, BWS) or a family history of childhood cancer (HCC); in contrast, 12 of 15 tumors (80%) obtained from patients without such a history contained CTNNB1 alterations. No somatic mutations were identified in the PTCH1, MLL2, and MLL3 genes in our cohort of HB samples. Although these results do not rule out the possibility that these genes may be mutated in a small fraction of HBs, they do suggest that mutations of these genes are not frequent events. It is possible that the PTCH1, MLL2, and MLL3 genes may be altered through alterna- tive genetic mechanisms or that these developmental pathways are disrupted through mutation of other pathway members not ana- lyzed in the current study. Comprehensive integrated genomic analysis of these tumors will be required for a more thorough understanding of the genetic landscape of HB. ACKNOWLEDGMENT This work was supported by the Sidney Kimmel Foundation for Cancer Research. DWP is a Graham Cancer Research Scholar at Texas Children’s Cancer Center. RSC is a St. Baldrick’s Foun- dation Fellow for Childhood Cancer Research. Rishikesh S. Chavan, MD Department of Pediatrics Kayuri U. Patel, BSc Angshumoy Roy, MD, PhD Department of Pathology and Immunology Patrick A. Thompson, MD Murali Chintagumpala, MD Department of Pediatrics John A. Goss, MD Jed G. Nuchtern, MD Michael E. DeBakey Department of Surgery Milton J. Finegold, MD Department of Pathology and Immunology D. Williams Parsons, MD, PhD* Department of Pediatrics Dolores H. Lo ´pez-Terrada, MD, PhD** Department of Pathology and Immunology Liver Tumor Center Texas Children’s Cancer Center Baylor College of Medicine Houston, Texas *Correspondence to: D. Williams Parsons, MD, PhD, Department of Pediatrics, Section of Hematology-Oncology, Baylor College of Medicine, 1102 Bates Ave., Suite 1030.15, Houston TX 77030. E-mail: dwparson@txch.org **Correspondence to: Dolores H. Lo ´pez-Terrada, MD, PhD, Division of Molecular Pathology, Department of Pathology, Texas Children’s Hospital, MC 1-2261, 6621 Fannin St., Houston, TX 77030. E-mail: dhterrad@texaschildrens.org Received 13 November 2011; Accepted 18 November 2011 ß 2011 Wiley Periodicals, Inc. DOI 10.1002/pbc.24045 Published online 19 December 2011 in Wiley Online Library (wileyonlinelibrary.com).