NRP1 knockdown inhibits the invasion and migration of rhabdoid tumor of the kidney cells.

PURPOSE: The aim of this study was to detect candidate oncogenes of rhabdoid tumor of the kidney (RTK) and evaluate their roles in RTK in vitro. METHODS: An integrated analysis of messenger RNA (mRNA) and microRNA (miRNA) sequencing was performed to determine the expression profile of exosome-derived miRNAs and mRNAs in human RTK-derived cell lines and a human embryonic renal cell line. A Gene Ontology enrichment analysis was performed to analyze the functional characteristics of differentially expressed mRNAs in RTK cells. Matrigel invasion and wound-healing assays were performed to evaluate the cell invasion and migration abilities. RESULTS: Forty mRNAs were highly expressed in RTK cells targeted by exosomal miRNAs, the expression of which was lower in RTK cells than in the controls. These mRNAs were primarily related to cell adhesion. Of these mRNAs, we selected neuropilin 1 (NRP1) as a candidate oncogene because its upregulated expression is associated with a poor prognosis of several types of tumors. RTK cells in which NRP1 had been knocked down exhibited decreased invasive and migratory abilities. CONCLUSION: Our study indicates that NRP1 acts as an oncogene by promoting the invasion and migration of RTK cells and that it could serve as a therapeutic target.

Current practice of diagnosis and treatment for rectourethral fistula in male patients with anorectal malformation: a multicenter questionnaire survey in Japan.

PURPOSE: Surgical procedures for anorectoplasty for anorectal malformations (ARMs), particularly rectourethral fistula (RUF), depend on the institution. We investigated the diagnosis and treatment of RUF in male patients with ARMs in Japan using a questionnaire survey. METHODS: An online survey inquiring about the diagnosis and treatment (diagnostic modalities, surgical approaches, fistula dissection devices, and fistula closure techniques) of each type of ARM in male patients was conducted among institutional members of the Japanese Study Group of Anorectal Anomalies. Fisher's exact test was used to compare surgical methods between posterior sagittal anorectoplasty (PSARP) and laparoscopy-assisted anorectoplasty (LAARP). RESULTS: Sixty-one institutions (100%) completed the survey. LAARP was the preferred approach for high-type ARM (75.4%). PSARP was preferred for intermediate-type ARM (59.0%). Monopolar devices were most commonly used (72.1%) for RUF dissection. Blunt dissection was more frequent in the PSARP group (PSARP vs. LAARP: 55.6 vs. 20.0%, p < 0.005). Cystoscopy/urethroscopy to confirm the extent of dissection was used more frequently in the LAARP group (70.0% vs. 25.0%, p < 0.005). Clips and staplers were used more frequently in the LAARP group (p < 0.05). CONCLUSION: Distinct fistula management strategies for PSARP and LAARP were revealed. Further studies are needed to investigate the postoperative outcomes associated with these practices.

Knockdown of TFAP2E results in rapid G2/M transition in oral squamous cell carcinoma cells.

TFAP2E is a member of the activator protein-2 transcription factor family and acts as a tumor suppressor in several types of cancer. Downregulation of TFAP2E expression is significantly associated with a shorter overall survival period in patients with oral squamous cell carcinoma (OSCC). To evaluate the molecular mechanisms by which TFAP2E suppresses the development or progression of OSCC, the present study investigated the effects of TFAP2E downregulation on OSCC-derived Ca9-22 and HSC-4 cells. The present study demonstrated that small interfering RNA mediated-knockdown of TFAP2E accelerated the proliferation of these OSCC cell lines compared with that in the control group, as determined by the standard water-soluble tetrazolium salt-8 assay. To analyze the cell cycle progression rate, the cell cycle distribution patterns of TFAP2E-knockdown and control cells cultured in the presence of nocodazole, which prevents the completion of mitosis, were analyzed by fluorescence-activated cell sorting at different time points. When analyzing cellular DNA contents, no major differences in cell cycle profiles were observed; however, the rate of increase in cells positive for histone H3 Serine 28 phosphorylation, a standard molecular marker of early M phase, was significantly higher in TFAP2E-knockdown cells than in the control cells. Collectively, these results suggested that TFAP2E may attenuate the proliferation of OSCC cells by regulating G2/M transition.

Does Congenital Biliary Dilatation Todani Type II (Diverticular Type) Really Exist?

AIM OF THE STUDY: The aim of the study is to clarify the clinicopathological and biliary morphological characteristics in reported cases of diverticular congenital biliary dilatation (CBD). METHOD: Using PubMed and the Japan Medical Abstracts Society, articles on possible diverticular CBD were extracted and the clinical pictures examined. We also sought evidence for definitions of diverticular CBD and the associated condition of pancreaticobiliary maljunction (PBM) using the original articles by Alonso-Lej and Todani. The characteristic biliary morphologies of cases with images were also investigated. RESULTS: Analyses of 211 possible cases superficially demonstrated multiple diverticula in 12 (12%) and single diverticulum in 89 (88%), with diverticula located in the upper (n = 38, 38%), middle (n = 32, 32%), or lower (n = 26, 26%) biliary tract in and presence of intra-diverticular stones, PBM, and biliary carcinoma in 23% (n = 18), 39% (n = 25), and 11% (n = 14), respectively. However, evidence defining diverticular CBD or justifying the lack of associated PBM was not demonstrated even in the original articles. Scrutiny of the biliary anatomy in 59 cases with images showed incorrect inclusions of types I or IV-A with an irregular biliary duct wall or dilated cystic duct, periampullary choledochal diverticula, or even solitary biliary cysts. Authentic diverticular CBD, representing the diverticulum connected to the middle of the common bile duct via a thin, patent stalk was seen in only 6 cases. CONCLUSION: Real diverticular CBD appears extremely rare. The lack of an objective definition allows wide interpretations of clinical pictures, creating inconsistencies in the diagnosis and treatment of CBD and raising questions regarding the utility of conventional classifications. LEVEL OF EVIDENCE: Level III.

Emergence of Phytobacter diazotrophicus carrying an IncA/C2 plasmid harboring bla NDM-1 in Tokyo, Japan.

Phytobacter diazotrophicus is an Enterobacterales species that was originally identified as a plant growth-promoting, Gram-negative bacterium. Recently, this species has been recognized as relevant to opportunistic human and nosocomial infections in clinical settings. Its frequent misidentification as other Enterobacterales species from clinical examination occasionally causes a delay in the identification of nosocomial outbreaks. Here, we report the emergence of New Delhi metallo-ß-lactamase (NDM)-producing P. diazotrophicus isolated from hospitalized pediatric patients and hospital environments in Tokyo, Japan. In our case, these isolates were found during an investigation of carbapenem-resistant Enterobacterales in relation to nosocomial infections. Whole-genome sequencing is useful for overcoming the difficulty of species identification. Furthermore, we found that bla NDM-1 was carried by an IncA/C2 plasmid (approximately 170 kbp), which was transferrable from the clinical isolates to the recipient strain Escherichia coli J53. Our study demonstrated that P. diazotrophicus behaves as a carrier of bla NDM-harboring plasmids, potentially disseminating resistance to carbapenems among Enterobacterales. IMPORTANCE Early detection of nosocomial outbreaks is important to minimize the spread of bacteria. When an outbreak is caused by multidrug-resistant bacteria such as carbapenem-resistant Enterobacterales, a delay in findings makes it difficult to control it because such bacteria often spread not only among human patients but also in hospital environments. Phytobacter diazotrophicus, an Enterobacterales species that has recently been found to be relevant to clinical settings, is often misidentified as other bacteria in clinical laboratories. Here, we found NDM-producing P. diazotrophicus in hospitalized pediatric patients and their environment in Tokyo, Japan. Given that the isolates carried bla NDM-1-harboring transferrable plasmids, the influence of such bacteria could be greater with the mediation of horizontal transfer of carbapenem resistance. Our findings suggest that P. diazotrophicus should be recognized as an NDM-carrier, for which more attention should be paid in clinical settings.

Usefulness of Thin-Slice Contrast-Enhanced Computed Tomography in Detecting Perforation Site in Congenital Biliary Dilatation: A Case Report.

The site of perforation is difficult to identify preoperatively in many cases with spontaneous perforation of congenital biliary dilatation (CBD). We report a case of spontaneous perforation of CBD in which the perforation site was identified preoperatively using thin-slice contrast-enhanced computed tomography (CT). The patient was a girl aged 1 year and 4 months. She was admitted to our hospital because of vomiting and diarrhea that had continued for 3 days prior to admission. Abdominal contrast CT on admission showed dilated common bile duct, thickening of the gall bladder wall, and marked ascites. In addition, an area of low density with a diameter of 1 cm was detected near the neck of the gallbladder. We evaluated the area via thin-slice contrast-enhanced CT and detected a defect in the wall of the bile duct. Cholangiography revealed abnormal confluence of the pancreaticobiliary duct and a protein plug in the common duct. A diagnosis of CBD with perforation of the bile duct was made, and surgery was performed. The intraoperative findings matched that seen on the enhanced CT. There are some reports of pseudocysts and fluid retention around the perforation site; however, no reports are found in which the perforation site was confirmed by preoperative CT. If localized fluid retention is observed in cases with biliary perforation, confirmation with thin-slice contrast-enhanced CT might be useful for identifying the perforation site.

Effects of dedifferentiated fat cells on neurogenic differentiation and cell proliferation in neuroblastoma cells.

PURPOSE: Mesenchymal stem cells (MSCs) can induce differentiation of neuroblastoma (NB) cells. Properties of dedifferentiated fat cells (DFATs) are similar to those of MSCs. Here, we investigated whether DFATs can induce NB cell differentiation and suppress cell proliferation. METHODS: DFATs were obtained from mature adipocytes isolated from adipose tissue from a ceiling culture. NB cells were cultured in a medium with or without DFATs and, subsequently, cultured in a DFAT-conditioned medium (CM) with or without phosphatidylinositol 3-kinase (PI3K) inhibitor. The neurite lengths were measured, and mRNA expression levels of the neurofilament (NF) and tubulin beta III (TUBß3) were assessed using quantitative real-time RT-PCR. Cell viability was assessed using the WST-1 assay. RESULTS: NB cells cultured with DFATs caused elongation of the neurites and upregulated the expression of NF and Tubß3. NB cells cultured in DFAT-CM demonstrated increased cell viability. NB cells cultured with DFAT-CM and PI3K inhibitors suppressed cell viability. NB cells cultured with DFAT-CM and PI3K inhibitor demonstrated increased neurite length and expression, and upregulation of Tubß3. CONCLUSION: The combined use of DFAT-CM and PI3K inhibitors suppresses the proliferation of NB cells and induces their differentiation. Thus, DFAT may offer new insights into therapeutic approaches in neuroblastoma.

Visceral Fat Area Measured by Abdominal Bioelectrical Impedance Analysis in School-Aged Japanese Children.

Abdominal bioelectrical impedance analysis (aBIA) has been in use to measure visceral fat area (VFA) in adults. Accurately measuring visceral fat using aBIA in children is challenging. Forty-six school-aged Japanese children aged 6-17 years (25 boys and 21 girls) were included in this study. All were measured, and their VFA obtained using aBIA (VFA-aBIA) and abdominal computed tomography (CT) (VFA-CT) were compared. VFA-aBIA was corrected using the Passing-Bablok method (corrected VFA-aBIA). The relationships between corrected VFA-aBIA and obesity-related clinical factors were analyzed, including non-alcoholic fatty liver disease (NAFLD) and serum leptin and adiponectin levels. Boys had higher VFA-CT than girls (p = 0.042), although no significant differences were found in their waist circumference, waist-to-height ratio, and body mass index. The corrected VFA-aBIA using y = 9.600 + 0.3825x (boys) and y = 7.607 + 0.3661x (girls) correlated with VFA-CT in both boys and girls. The corrected VFA-aBIA in patients with NAFLD was higher than that in those without NAFLD. Serum leptin and adiponectin levels were positively and negatively correlated with corrected VFA-aBIA, respectively. In conclusion, corrected VFA-aBIA was clearly correlated with VFA-CT and was related to NAFLD and serum leptin and adiponectin levels in school-aged Japanese children.

A phase III clinical trial evaluating efficacy and safety of minimal residual disease-based risk stratification for children with acute myeloid leukemia, incorporating a randomized study of gemtuzumab ozogamicin in combination with post-induction chemotherapy for non-low-risk patients (JPLSG-AML-20).

The purpose of this study is to establish a treatment with appropriate intensity for children (<16 years old at diagnosis) with de novo acute myeloid leukemia (excluding acute promyelocytic leukemia and myeloid leukemia associated with Down syndrome) according to a risk stratification based on recurrent leukemic cytogenetic abnormalities and flow-cytometric minimal residual disease at end of initial induction chemotherapy and to validate the safety and efficacy of gemtuzumab ozogamicin (GO)-combined post-induction chemotherapy for the non-low-risk (non-LR) patients. The primary endpoint of this phase III study is three-year disease-free survival rate, which will be compared between the GO and non-GO arms of the non-LR (intermediate-risk and high-risk [HR]) patients. All HR patients will be allocated to allogeneic hematopoietic stem cell transplantation in first remission. This trial has been registered at the Japan Registry of Clinical Trials (jRCTs041210015).

Oral benzo[a]pyrene administration attenuates dextran sulfate sodium-induced colitis in mice.

Benzo[a]pyrene (BaP) is an environmental pollutant produced by combustion processes and is present in grilled foods as well as in tobacco smoke. BaP acts as an agonist for the aryl hydrocarbon receptor (AHR), and is metabolized by AHR-inducing enzymes. BaP metabolism can result in either detoxification or metabolic activation, the latter leads to an increased risk of disease, particularly lung cancer and cardiovascular disease, in a context-dependent manner. Although AHR activation has been thought to protect against inflammatory bowel disease, it remains unknown whether BaP exerts a protective or deleterious effect on colitis. In this study, we examined the effect of oral BaP administration on colitis induced by dextran sulfate sodium (DSS) in mice, an animal model of inflammatory bowel disease. BaP administration attenuated weight loss, shortening of the colon, disease activity index scores, and histological damage in DSS-induced colitis mice. BaP also suppressed colonic expression of inflammation-associated genes and plasma interleukin-6 secretion induced by DSS treatment. BaP-DNA adduct formation, a marker of BaP metabolic activation, was not enhanced in the colon after DSS treatment. Thus, oral BaP exerts an anti-inflammatory effect on DSS-induced colitis, without the toxicity associated with metabolic activation. The results provide insights into the disease-specific roles of BaP.

FGFR2 loss sensitizes MYCN-amplified neuroblastoma CHP134 cells to CHK1 inhibitor-induced apoptosis.

Checkpoint kinase 1 (CHK1) plays a key role in genome surveillance and integrity throughout the cell cycle. Selective inhibitors of CHK1 (CHK1i) are undergoing clinical evaluation for various human malignancies, including neuroblastoma. In this study, one CHK1i-sensitive neuroblastoma cell line, CHP134, was investigated, which characteristically carries MYCN amplification and a chromosome deletion within the 10q region. Among several cancer-related genes in the chromosome 10q region, mRNA expression of fibroblast growth factor receptor 2 (FGFR2) was altered in CHP134 cells and associated with an unfavorable prognosis of patients with neuroblastoma. Induced expression of FGFR2 in CHP134 cells reactivated downstream MEK/ERK signaling and resulted in cells resistant to CHK1i-mediated cell growth inhibition. Consistently, the MEK1/2 inhibitor, trametinib, potentiated CHK1 inhibitor-mediated cell death in these cells. These results suggested that FGFR2 loss might be prone to highly effective CHK1i treatment. In conclusion, extreme cellular dependency of ERK activation may imply a possible application for the MEK1/2 inhibitor, either as a single inhibitor or in combination with CHK1i in MYCN-amplified neuroblastomas.

Laparoscopic approach for abdominal neuroblastoma in Japan: results from nationwide multicenter survey.

BACKGROUND: Some neuroblastoma (NB) cases are suitable for minimally invasive surgery (MIS), but indication and technical issue are unclear. We assessed the current status of MIS for abdominal NB after mass screening period in Japan. METHODS: Preliminary questionnaires requesting the numbers of NB cases that underwent MIS from 2004 to 2016 were sent to 159 Japanese institutes of pediatric surgery. The secondary questionnaires were then sent to the institutions that reported MIS cases of NB in order to collect detailed data. RESULTS: One hundred and thirty-four (84.2%) institutions responded to the preliminary questionnaires, and 83 (52.2%) reported managing operative cases. The total number of operative cases was 1496. MIS was performed for 175 (11.6%) cases, of which the completed forms of 140 patients were returned, including 100 abdominal NB cases. The male/female ratio was 51/49. Forty-seven cases underwent a laparoscopic biopsy, and 2 (4.3%) cases were converted to laparotomy due to bleeding. Sixty-five cases underwent MIS for radical resection, and 7 (10.8%) were converted to laparotomy. The reasons for open conversion were bleeding and severe adhesion. Regarding open conversion, there were no significant relationships between conversion and neo-adjuvant chemotherapy, biopsies, stage, size, or MYCN amplification. We found no relationship between resectability and vascular encasement in this study. There was relationship between the resected tumor size and the patients' height, which was expressed using the following formula: [Formula: see text] (x, patients height, y, tumor size; p = 0.004219, SE: 1.55566). Postoperative complications after radical resection were recognized in 7 (10.8%) cases. CONCLUSIONS: MIS was performed in limited cases of abdominal NB. A laparoscopic biopsy with careful attention to bleeding is feasible. The resected tumor size was shown to correlate with the patients' height. Tumor size within 6 cm of maximum diameter can be resected safely.

Ileal Dieulafoy lesion arose 15 years after partial small bowel resection for meconium obstruction of the neonate: a case report.

BACKGROUND: Anastomotic or perianastomotic ulcers present with symptoms such as chronic anaemia and occult bleeding as long-term complications of bowel resection performed in infancy. CASE PRESENTATION: Herein, we describe a 15-year-old girl with a history of surgery for meconium obstruction without mucoviscidosis in infancy who was hospitalized with chief complaints of presyncope and convulsions. Seven hours after admission, she developed melena and went into shock. An emergency laparotomy was performed, and a Dieulafoy lesion was detected near the site of ileal anastomosis from the surgery that had been performed during infancy. CONCLUSIONS: Although overt massive lower gastrointestinal bleeding necessitating emergency care is rare in the long term after infant bowel resection, Dieulafoy lesions can cause serious bleeding, requiring rapid life-saving haemostatic procedures.

Exosomal miR-214-3p as a potential novel biomarker for rhabdoid tumor of the kidney.

PURPOSE: Rhabdoid tumor of the kidney (RTK) is a rare, highly aggressive pediatric renal tumor. No specific biomarkers are available for detection of RTK, and the initial differential diagnosis from other pediatric abdominal tumors, including neuroblastoma (NB), is difficult. Exosomal miRNAs are novel cancer biomarkers that can be detected in biological fluids. We explored candidate RTK-specific exosomal miRNAs as novel biomarkers of RTK. METHODS: Exosomal miRNAs were collected from conditioned media of human RTK-derived cell lines, a human embryonic renal cell line, and human NB-derived cell lines. miRNA sequencing (miRNA-Seq) was performed to detect candidate RTK-specific exosomal miRNAs. The exosomal miRNA expression in conditioned media of tumor cell lines and serum from RTK xenograft-bearing mice was analyzed by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). RESULTS: The expression of exosomal miR-214-3p detected by miRNA-Seq was highest in RTK-derived cell lines. Exosomal miR-214-3p expression level determined by qRT-PCR was significantly higher in RTK-derived cell lines than in the human embryonic renal cell line or NB-derived cell lines. Furthermore, the serum exosomal miR-214-3p expression level was significantly higher in RTK xenograft mice than controls. CONCLUSION: Our data indicated that exosomal miR-214-3p has potential as a novel biomarker of RTK.

Current thoracoscopic approach for mediastinal neuroblastoma in Japan-results from nationwide multicenter survey.

BACKGROUND: Minimally invasive surgery (MIS) is appropriate for the treatment of some neuroblastomas (NBs); however, the indications and technical issues are unclear. This study aimed to clarify the current status of MIS for mediastinal NB in Japan. METHODS: Preliminary questionnaires requesting the numbers of neuroblastoma cases in which MIS was performed from 2004 to 2016 were sent to 159 Japanese institutes of pediatric surgery. Secondary questionnaires were sent to institutions with MIS cases to collect detailed data. RESULTS: One hundred thirty-four (84.2%) institutions returned the preliminary questionnaire and 83 institutions (52.2%) reported a total of 1496 operative cases. MIS was performed for 175 (11.6%) cases. Among the 175 cases, completed forms of 140 patients were returned and 40 (male, n = 28; female, n = 12) cases had mediastinal NB. Fourteen patients received thoracoscopic biopsy, none were converted to thoracotomy. Twenty-eight patients received MIS for radical resection, none were converted to thoracotomy. Perioperative complications (Horner's syndrome) were recognized after radical resection in one (2.5%) case. CONCLUSIONS: MIS was performed in a limited number of mediastinal NB cases. A thoracoscopic approach would be feasible for mediastinal NB.

[Prediction of Prognosis in Breast Carcinoma Using Klotho Immunohistochemistry].

Klotho is one of the known anti-aging genes, and functions as an inhibitor of the insulin-like growth factor 1(IGF-1) pathway. However, the clinical significance of Klotho expression in cancer tissues have not been elucidated yet. In this study, we aimed to investigate the clinical significance of Klotho expression in breast cancer patients. We evaluated Klotho expression through immunohistochemical analysis and evaluating Ki-67 positive cell index in 142 patients who underwent surgery for breast cancer in our hospital. There was no significant correlation between age, menopausal state, historical type, hormone status, HER2 status, and distant metastases. High expression of Klotho was observed in the non-invasive compared to the invasive ductal carcinomas. The number of metastatic lymph nodes, clinical stage, and tumor size were correlated to Klotho expression level in the cancer tissues. The Klotho positive group exhibited low score for Ki-67 positive cell index than the Klotho negative group. No significant correlation in cumulative survival rates between Klotho positive and Klotho negative groups was observed. The Klotho negative group exhibited good prognosis than the Klotho positive group for the disease- free survival after the operation. These results suggest that the analysis Klotho expression in the breast cancer tissues using immunohistochemistry is a useful tool to assess the disease-free survival for breast cancer patients.

Comparative analysis of the clinical characteristics and outcomes of patients with Wilms tumor in the United Kingdom and Japan.

BACKGROUND: Wilms tumor (WT) demonstrates epidemiological differences by world region and ethnicity. To enhance understanding of these differences, we retrospectively analyzed clinical trial data sets from the UK and Japan over a 20-year period. PROCEDURE: We used data from three consecutive clinical trials in the UK and a single study in Japan that enrolled patients diagnosed during 1996-2015, to compare clinical characteristics and outcomes between countries. RESULTS: During 1996-2015, 1395 patients in the UK and 537 in Japan were included. Japanese patients have a significantly younger median age at diagnosis than those in the UK (28 months vs 39 months). The proportion of patients with stage IV, large tumors, and anaplastic histology appears to be higher in the UK than in Japan (18% vs 11%, 62% vs 49%, 8% vs 3%, respectively). During 2005-2015, 77 hospitals treated WT in Japan compared with only 20 hospitals in the UK. Five-year overall survival of patients with WT was over 90% in both countries, but five-year event-free survival of patients with stage IV was significantly lower in Japan than in the UK (50.0% vs 76.2%, P = 0.001). CONCLUSIONS: Differences in age of onset, tumor size at diagnosis, and histology may reflect differences in the genetic background of patients with WT between countries, but population-based phenotype-genotype data are lacking. The difference in survival probability for stage IV patients may be due to different diagnostic criteria or different treatment strategies. Prospective, international clinical studies including genomic analyses are needed to confirm these findings and improve clinical practice.

Frequent breakpoints of focal deletion and uniparental disomy in 22q11.1 or 11.2 segmental duplication region reveal distinct tumorigenesis in rhabdoid tumor of the kidney.

SMARCB1 is mutated in most rhabdoid tumors (RTs) developing in the kidney (RTK) and various other organs. Focal deletions found in patients with 22q11.2 deletion syndrome show breakpoints within clusters of segmental duplications (SDs), and those in some RTs show breakpoints in the 22q11-q12 region. SDs are known to cause focal deletion mediated by non-allelic homologous recombination. The present study identified SMARCB1 alterations in all 30 RTKs, using SNP array CGH, MLPA, and sequence analyses. Twenty-eight tumors had a total of 51 breakpoints forming focal 22q deletion and/or uniparental disomy (22qUPD), and the other two had compound mutation with no breakpoints in 22q. Twenty-four (47.1%) of the 51 breakpoints were within SDs, and occurred in 16 (53.3%) of the 30 tumors. The association of breakpoints with SDs was found not only in focal deletion, but also in 22qUPD, indicating that SDs mediate the first and second hits (focal deletion) and the second hit (22qUPD) of SMARCB1 alteration. Of the 51 breakpoints, 14 were recurrent, and 10 of the 14 were within SDs, suggesting the presence of hotspots in the 22q11.2 region. One recurrent breakpoint outside SDs resided in SMARCB1, suggesting inactivation of the gene by out-of-frame fusion. The association between SDs and focal deletion has been reported in two other types of cancer. RTKs may be the third example of SD-associated tumors. Thus, the present study indicated that RTKs exploit genomic instability in the 22q11.1-11.2 SDs region, and 22qUPD caused by mitotic recombination may also be mediated by SDs.