A rare case of esophageal metastasis from signet-ring cell carcinoma of the cecum.

BACKGROUND: Metastatic esophageal cancer is rare. Its common primary lesions include lung cancer and breast cancer. Metastatic esophageal cancer originating from colorectal cancer is rarer. CASE PRESENTATION: A 79-year-old woman visited our hospital because of lower abdominal discomfort. She was endoscopically diagnosed with type 0-IIa + IIc cancer of the cecum, and biopsy of the lesion showed signet-ring cell carcinoma. With a preoperative clinical staging of cStage I (cT2, cN0, cM0), the patient underwent laparoscopic ileocecal resection with D3 lymphadenectomy. Histopathological examination of the resected specimens revealed signet-ring cell carcinoma [type 4, pT4a, pN3 (No. 203), M0, pRM1, stage IIIc, R1]. Despite radial margin positivity, the patient refused resection of the residual tumor and received oral tegafur and uracil. KRAS mutation test showed KRAS wild-type colon cancer, but she refused anti-epidermal growth factor receptor therapy. One year after surgery, her blood carcinoembryonic antigen concentration elevated. Colonoscopy showed anastomotic recurrence and biopsy of the lesion showed signet-ring cell carcinoma. Upper gastrointestinal endoscopy showed multiple longitudinal submucosal tumors with erosions on their surfaces in the esophagus. Tumor biopsy revealed signet-ring cell carcinoma. Immunohistochemistry showed that the histological type of the esophageal tumors was the same as that of the primary colon cancer. Based on these findings, the esophageal tumors were diagnosed with metastasis from signet-ring cell carcinoma of the cecum. The oral chemotherapy was replaced with FOLFOX plus bevacizumab. However, the patient's condition required treatment discontinuation, and she died of cancer progression 1 year and 5 months after surgery. CONCLUSIONS: To our knowledge, this is the first case report on metastatic esophageal cancer from signet-ring cell carcinoma of the cecum. Esophagoscopy showed multiple longitudinal submucosal tumors, which is similar to an endoscopic finding of intramural metastasis from primary esophageal cancer. We consider that the multiple longitudinal submucosal tumors are a notable feature of our case. When metastatic esophageal cancer is suspected, clinicians, endoscopists, and pathologists should consider signet-ring cell carcinoma of the colon as one of potential primary lesions. This consideration could lead the specialists to appropriate examinations and treatments, thereby improving clinical outcomes in patients with the metastasis.

Validation of a genotyping technique for a surrogate marker of HLA-B∗58:01 for allopurinol-induced Stevens-Johnson syndrome and toxic epidermal necrolysis in the Japanese population.

Stevens-Johnson syndrome and toxic epidermal necrolysis (SJS/TEN) are rare but severe cutaneous adverse drug reactions. Certain human leukocyte antigen (HLA) types have been associated with SJS/TEN onset, e.g., HLA-B∗58:01 with allopurinol-induced SJS/TEN, but HLA typing is time-consuming and expensive; thus, it is not commonly used in clinical situations. In the previous work, we demonstrated that the single-nucleotide polymorphisms (SNP) rs9263726 was in absolute linkage disequilibrium with HLA-B∗58:01 in the Japanese population, and can be used as a surrogate marker for the HLA. Here, we developed a new genotyping method for the surrogate SNP using the single-stranded tag hybridization chromatographic printed-array strip (STH-PAS) technique and performed an analytical validation. The results of genotyping rs9263726 using STH-PAS correlated well with those obtained using the TaqMan SNP Genotyping Assay for 15 HLA-B∗58:01-positive and 13 HLA-B∗58:01-negative patients (analytical sensitivity and specificity were both 100%). Additionally, at least 1.11 ng of genomic DNA was sufficient to digitally and manually detect positive signals on the strip. Robustness studies showed that the annealing temperature (66 °C) was the most important condition related to reliable results. Collectively, we developed an STH-PAS method that can rapidly and easily detect rs9263726 for predicting SJS/TEN onset.

CRISPR/Cas9-Mediated Induction of Relapse-Specific NT5C2 and PRPS1 Mutations Confers Thiopurine Resistance as a Relapsed Lymphoid Leukemia Model.

6-Mercaptopurine (6-MP) is a key component in maintenance therapy for childhood acute lymphoblastic leukemia (ALL). Recent next-generation sequencing analysis of childhood ALL clarified the emergence of the relapse-specific mutations of the NT5C2 and PRPS1 genes, which are involved in thiopurine metabolism. In this scenario, minor clones of leukemia cells could acquire the 6-MP-resistant phenotype as a result of the NT5C2 or PRPS1 mutation during chemotherapy (including 6-MP treatment) and confer disease relapse after selective expansion. Thus, to establish new therapeutic modalities overcoming 6-MP resistance in relapsed ALL, human leukemia models with NT5C2 and PRPS1 mutations in the intrinsic genes are urgently required. Here, mimicking the initiation process of the above clinical course, we sought to induce two relapse-specific hotspot mutations (R39Q mutation of the NT5C2 gene and S103N mutation of the PRPS1 gene) into a human lymphoid leukemia cell line by homologous recombination (HR) using the CRISPR/Cas9 system. After 6-MP selection of the cells transfected with Cas9 combined with single-guide RNA and donor DNA templates specific for either of those two mutations, we obtained the sublines with the intended NT5C2-R39Q and PRPS1-S103N mutation as a result of HR. Moreover, diverse in-frame small insertion/deletions were also confirmed in the 6-MP-resistant sublines at the target sites of the NT5C2 and PRPS1 genes as a result of nonhomologous end joining. These sublines are useful for molecular pharmacological evaluation of the NT5C2 and PRPS1 gene mutations in the 6-MP sensitivity and development of therapy overcoming the thiopurine resistance of leukemia cells. SIGNIFICANCE STATEMENT: Mimicking the initiation process of relapse-specific mutations of the NT5C2 and PRPS1 genes in childhood acute lymphoblastic leukemia treated with 6-mercaptopurine (6-MP), this study sought to introduce NT5C2-R39Q and PRPS1-S103N mutations into a human lymphoid leukemia cell line by homologous recombination using the CRISPR/Cas9 system. In the resultant 6-MP-resistant sublines, the intended mutations and diverse in-frame small insertions/deletions were confirmed, indicating that the obtained sublines are useful for molecular pharmacological evaluation of the NT5C2 and PRPS1 gene mutations.

The Impact of Pretreatment Esophageal Stenosis on Survival of Esophageal Cancer Patients.

BACKGROUND: Little is known about the survival impacts of pretreatment cancerous stenosis on patients with esophageal carcinoma (EC). METHODS: The clinicopathologic characteristics of patients who underwent surgery for EC between January 2010 and December 2018 were retrospectively reviewed. Esophageal stenosis was defined as present when a thin endoscope could not be passed through the tumor site. The impacts of stenosis on overall survival (OS) and cancer-specific survival (CSS) were evaluated using Cox hazards analysis. RESULTS: Of the 496 EC patients in this study, 51 (10.3 %) had pretreatment esophageal stenosis. Stenosis was associated with lower body mass index (P < 0.001) and higher pStage (P < 0.001). The 3-year OS rate for the patients with stenosis was significantly poorer than for the patients without stenosis (40.2 % vs 69.6 %; hazard ratio [HR], 2.19; P < 0.001). The survival outcomes, especially CSS, for the patients with stenosis were significantly poorer than for the patients without stenosis for both pStage II-III (P = 0.009) and pStage IV (P = 0.006) disease. The OS and CSS curves were well stratified by the presence of stenosis even in early-stage (pStage II) patients (P = 0.04 and P < 0.01, respectively). Multivariable analysis showed esophageal stenosis, pStage III-IV disease, and non-curative resection to be independently associated with poor OS (HR, 1.61; P = 0.02) and poor CSS (HR,1.67; P = 0.02). Higher pStage was an independent predictor of poor CSS for patients without stenosis, but not for those with stenosis. CONCLUSIONS: Esophageal carcinoma patients with pretreatment stenosis had significantly poorer survival outcomes, especially poorer CSS, than those without stenosis in both early- and advanced-stage diseases.

[Pharmacogenomics in hematological malignancy].

Therapeutic response and drug-induced toxicity have been reported to be associated with genetic variants of drug-metabolizing enzymes and transporters. Recently, new causative variants associated with drug response have been reported by genome-wide association studies (GWASs). Additionally, therapeutic response has been predicted using a model of multiple single-nucleotide polymorphisms. In acute lymphoblastic leukemia (ALL), the genetic variants of NUDT15 associated with therapeutic response to 6-mercaptopurine (6-MP) have been reported by GWASs, and the frequency of NUDT15 variants was higher in Asians. Then, several reports on NUDT15 genetic variants associated with 6-MP-induced toxicities and the tolerable doses and outcomes of 6-MP therapy for ALL have been published in Asian countries. The drugs used in treating hematological malignancies have reported new genetic variants associated with its therapeutic response. However, the association between these genetic variants has not been validated in other populations. Here, we reviewed recent reports on the association between the genetic variants and response to drugs used in treating hematological malignancies, such as 6-MP, cytarabine, methotrexate, and vincristine.

Long-term outcome of metachronous, multiple, early Epstein-Barr virus-associated gastric carcinoma: a case report.

Background: Epstein-Barr virus is associated with various malignancies. Epstein-Barr virus-associated gastric carcinoma (EBVaGC) was reported in 1990. While gastric carcinoma with lymphoid stroma (GCLS) is a rare gastric cancer, 80% to 90% of these tumors are associated with Epstein-Barr virus infection. Case Description: The patient was a 67-year-old male in 2004, when he underwent laparoscopy-assisted distal gastrectomy with Billroth I reconstruction to treat early stage 0-IIc gastric cancer; the pathological diagnosis was moderately differentiated adenocarcinoma, pT1b, pN0, stage IA with a negative margin. In 2009, endoscopic submucosal dissection (ESD) was performed on reoccurring stage 0-IIc gastric cancer; pathology results identified well-differentiated adenocarcinoma, pT1b, Ly0, V0, pHM0, pVM0. Although further gastric resection was recommended, the patient declined the procedure and opted to receive only follow-up evaluation. During the follow-up period, upper gastrointestinal (GI) endoscopy revealed a protruding mass on the remaining gastric fundus; biopsy indicated a poorly differentiated adenocarcinoma. Approximately 15 years after the initial treatment, the patient underwent total resection of the remnant stomach and Roux-en-Y reconstruction. The histopathological diagnosis was gastric cancer, pT1b, N0, no lymphatic and venous invasion, stage IA with lymphoid stroma and lymphocyte infiltration associated with formation of lymphoid follicles. Immunohistochemistry with EBV-encoded RNA in situ hybridization (EBER-ISH) was positive, resulting in diagnosis of EBVaGC. Retrospective EBER-ISH performed on resected specimens from the 2 prior surgeries yielded similar results. Furthermore, immunohistochemistry using anti-programmed death ligand 1 (PD-L1) antibody demonstrated an increase in the combined positive score (CPS) over time. Conclusions: This report describes the rare case of a patient who experienced 3 occurrences of EBVaGC at different times and locations over 15 years and discusses the clinical relevance in the context of a literature review. It aims to increase awareness among clinicians and pathologists of the necessity of considering EBVaGC when deciding on the treatment strategy after reoccurrence of gastric cancer.

Prominence of NUDT15 genetic variation associated with 6-mercaptopurine tolerance in a genome-wide association study of Japanese children with acute lymphoblastic leukaemia.

Inherited genetic variation is associated with 6-mercaptopurine (6-MP) dose reduction and frequent toxicities induced by 6-MP. However, the tolerable dose for 6-MP is not fully predicted by the known variation in NUDT15 and TPMT among Asian children with acute lymphoblastic leukaemia (ALL). We performed a genome-wide association study (GWAS) related to 6-MP dose among Japanese children with ALL. This GWAS comprised 224 patients previously enrolled in Tokyo Children's Cancer Study Group clinical studies with replication attempted in 55 patients. Genome-wide single nucleotide polymorphism (SNP) genotypes were evaluated for association with average 6-MP dose during the initial 168 days of maintenance therapy. Possible associations were observed across five gene-coding regions, among which only variants at 13q14.2 were significant and replicated genome-wide (rs116855232, NUDT15, ß = -10.99, p = 3.7 × 10-13 ). Notable findings were observed for variants in AFF3 (rs75364948, p = 2.05 × 10-6 ) and CHST11 (rs1148407, p = 2.09 × 10-6 ), but were not replicated possibly due to small numbers. A previously reported candidate SNP in MTHFR was associated with higher average 6-MP dose (rs1801133, p = 0.045), and FOLH1 (rs12574928) was associated in an evaluation of candidate regions (padjust  = 0.013). This study provides strong evidence that rs116855232 in NUDT15 is the genetic factor predominantly associated with 6-MP tolerable dose in children in Japan.

NUDT15 polymorphism and NT5C2 and PRPS1 mutations influence thiopurine sensitivity in acute lymphoblastic leukaemia cells.

In chemotherapy for childhood acute lymphoblastic leukaemia (ALL), maintenance therapy consisting of oral daily mercaptopurine and weekly methotrexate is important. NUDT15 variant genotype is reportedly highly associated with severe myelosuppression during maintenance therapy, particularly in Asian and Hispanic populations. It has also been demonstrated that acquired somatic mutations of the NT5C2 and PRPS1 genes, which are involved in thiopurine metabolism, are detectable in a portion of relapsed childhood ALL. To directly confirm the significance of the NUDT15 variant genotype and NT5C2 and PRPS1 mutations in thiopurine sensitivity of leukaemia cells in the intrinsic genes, we investigated 84 B-cell precursor-ALL (BCP-ALL) cell lines. Three and 14 cell lines had homozygous and heterozygous variant diplotypes of the NUDT15 gene, respectively, while 4 and 2 cell lines that were exclusively established from the samples at relapse had the NT5C2 and PRPS1 mutations, respectively. Both NUDT15 variant genotype and NT5C2 and PRPS1 mutations were significantly associated with DNA-incorporated thioguanine levels after exposure to thioguanine at therapeutic concentration. Considering the continuous exposure during the maintenance therapy, we evaluated in vitro mercaptopurine sensitivity after 7-day exposure. Mercaptopurine concentrations lethal to 50% of the leukaemia cells were comparable to therapeutic serum concentration of mercaptopurine. Both NUDT15 variant genotype and NT5C2 and PRPS1 mutations were significantly associated with mercaptopurine sensitivity in 83 BCP-ALL and 23 T-ALL cell lines. The present study provides direct evidence to support the general principle showing that both inherited genotype and somatically acquired mutation are crucially implicated in the drug sensitivity of leukaemia cells.

Importance of NUDT15 Polymorphisms in Thiopurine Treatments.

Thiopurines, mercaptopurine, and azathioprine are used as immunosuppressants in the treatments of inflammatory bowel disease, rheumatoid arthritis, and organ transplantation and as chemotherapeutic drugs for the treatment of acute leukemia and chronic myeloid leukemia. This drug class sometimes causes severe adverse reactions, including bone marrow suppression and hair loss. Genetic polymorphisms of the metabolizing enzyme thiopurine S-methyltransferase have been used for predicting these reactions in Caucasians, but these allele frequencies are less frequently observed in Asian populations. Recently, nudix hydrolase 15 (NUDT15) polymorphisms have been shown to play an important role in thiopurine-induced adverse reactions in Asians. In this review, we summarize the NUDT15 studies, mainly in Asian countries, and their implementation in several countries.

Heterochronous Suture Line Recurrences in the Jejunal Pouch following Total Gastrectomy for Stage II Gastric Cancer: A Case Report and Literature Review.

We report the case of a 65-year-old male who developed heterochronous local recurrences of gastric cancer in the jejunal pouch (J-pouch) four times after total gastrectomy. He underwent total gastrectomy, J-pouch, and Roux-en-Y reconstruction for stage II gastric cancer in 2005. Four local recurrences appeared on the esophago-jejunal anastomosis, the suture line within the pouch, the esophago-jejunal anastomosis, and the anastomosis between the jejunum and Y-loop, which were resected by partial excision or endoscopic submucosal dissection. Suture line recurrence of gastric cancer is rare. The common features for each recurrence included the surgically negative resection margins, observation of the same histopathological subtype, absence of remote metastasis or peritoneal seeding, and the recurrence on the anastomotic suture line, suggesting that the cause of recurrence was the implantation of exfoliated cancer cells probably in the suture line. However, there is no established procedure for preventing implantation recurrence currently, the effectiveness of lumen lavage is suggested.

Successful combination of endoscopic and laparoscopic removal of multiple ingested needles: A case report.

RATIONALE: Foreign body (FB) ingestion is a relatively common clinical situation in the emergency department. However, multiple sharply pointed foreign bodies located in different organs are rare conditions and no definite treatment guidelines has been established. PATIENT CONCERNS: A 31-year-old amateur magician visited the outpatient clinic with a chief complaint of epigastric discomfort. He might have accidentally swallowed some needles while practicing a magic trick 2 days before. DIAGNOSIS: Imaging tests revealed 1 needle was stuck in the left liver lobe through the stomach wall, 1 was in the third portion of the duodenum, 3 were in the ascending colon, and 2 were in the transverse colon. INTERVENTIONS: A needle in the duodenum and 5 in the colon were removed by endoscopy. The needle stuck in the liver from the stomach was not visible inside the stomach and was successfully removed by laparoscopy a few days later. OUTCOMES: The patient was able to tolerate an oral diet and was discharged on postoperative day 4 without any complications. LESSONS: Developing a treatment plan in cases of multiple sharp FB may be difficult. A multidisciplinary team of endoscopists and surgeons is needed to determine the best possible treatment plan. This experience illustrates the importance of the planning of the sequence and method of removal of multiple foreign bodies from the gastrointestinal tract.

Anomalies of the right vertebral vein increasing the difficulty of lymph-node dissection along the right recurrent laryngeal nerve: a single-institution, retrospective study.

BACKGROUND: Radical lymph-node dissection along the recurrent laryngeal nerves (RLN) improves the prognosis of patients with esophageal cancer. The RLN is a landmark for achieving adequate lymph-node dissection. However, the right RLN is sometimes covered by the right vertebral veins (VVs), making it undetectable. We investigated the relationship between this anomaly of the right VVs and the challenges of performing lymphadenectomy along the right RLN. METHODS: Patients with esophageal cancer, who underwent thoracoscopic esophagectomy with radical lymph-node dissection, were registered. The patterns of the right VVs were evaluated by preoperative computed tomography. The time required for identifying the right RLN or completing the lymphadenectomy was determined by reviewing surgical videos. RESULTS: In total, 178 patients were enrolled. Eighty patients (45%) had right VVs passing dorsal to the right subclavian artery (Dorsal group). More time was required to detect the right RLN in these cases (11 vs 9.5 min for the other cases, p = 0.034). In the Dorsal group, there were 15 patients who had specific VV patterns: The right VV converged on the lower portion of the right brachiocephalic vein (BCV), or passed through to the more medial side of the mediastinum. These patients required more time for detecting the right RLN (25 vs 9 min, p < 0.0001) and for completing the lymphadenectomy (41 vs 32 min, p = 0.048) than the other cases. CONCLUSION: The right VVs behind the subclavian artery, joining the lower part of the BCV or passing through the medial side, made it difficult to identify the right RLN and complete the lymphadenectomy.

Tolerability of Erythrocyte Ribavirin Triphosphate Concentrations Depends on the ITPA Genotype.

BACKGROUND: Ribavirin (RBV) is an antiviral drug that is part of the current standard therapy for chronic hepatitis C (CHC). It is enzymatically converted to ribavirin triphosphate (RTP) that inhibits the activity of viral RNA polymerase, thereby preventing viral replication. However, one of its adverse effects includes hemolytic anemia that limits its application. The variant of ITPA (inosine triphosphatase), which dephosphorylates inosine triphosphate to inosine monophosphate, is a protective factor for RBV-induced anemia. RTP is an important metabolite required for ribavirin action. This study evaluated the time-dependent association of RTP concentrations in erythrocytes, RBV-induced toxicity, and virological response to RBV treatment for hepatitis C. METHODS: A total of 28 Japanese patients with CHC were treated with RBV/peg-interferon/simeprevir or RBV/sofosbuvir and were genotyped for ITPA variants (rs1127354 and rs7270101). We measured RTP concentrations in erythrocytes in a total of 76 samples collected at 4, 8, and 12 weeks from the initiation of treatment. RESULTS: The ITPA rs1127354 variant was found in 7 patients. This was associated with significantly higher RTP concentrations in erythrocytes than in the wild-type patients (P < 0.001). Moreover, a significant correlation was observed between RTP concentrations and decline in hemoglobin (Hb) levels from baseline values in ITPA wild type and rs1127354 variant 12 weeks after treatment initiation (P < 0.01; r = -0.618 and -0.967, respectively). Multiple regression analysis revealed that ITPA genotype and erythrocyte RTP concentrations were major factors associated with reduced Hb levels in RBV therapy for CHC. However, we did not find any association between erythrocyte concentrations and virological response. CONCLUSIONS: The increased tolerability to RTP concentrations in erythrocytes in the ITPA variant rs1127354 plays a role in preventing RBV-induced severe anemia in this ITPA variant.

Phase II feasibility study of preoperative concurrent chemoradiotherapy with cisplatin plus 5-fluorouracil and elective lymph node irradiation for clinical stage II/III esophageal squamous cell carcinoma.

BACKGROUND: Preoperative chemoradiotherapy (CRT) is a standard treatment for stage II/III esophageal cancer. Preoperative chemotherapy is also considered a standard treatment for stage II/III esophageal squamous cell carcinoma (ESCC) in patients who undergo radical lymph node dissection. We conducted a feasibility study of preoperative CRT with cisplatin plus 5-fluorouracil (CF) and elective lymph node irradiation followed by esophagectomy with radical lymph node dissection in patients with stage II/III ESCC. METHODS: Patients with clinical stage II/III, excluding T4, ESCC (International Union Against Cancer TNM classification system, 6th edition) were eligible. Chemotherapy comprised two courses of CF infusion repeated after 4-weeks. Radiation therapy was concurrently administered to the primary tumor, metastatic lymph nodes, and regional lymph nodes at a dose of 41.4 Gy. After the completion of CRT, transthoracic esophagectomy with 2-3 fields lymphadenectomy was performed. The primary endpoint was the completion rate of protocol treatment with R0 resection. RESULTS: Thirty-one eligible patients were enrolled. During CRT, the most common grade 3 or 4 toxicities were leukopenia (65%), neutropenia (65%), anemia (13%), thrombocytopenia (13%), febrile neutropenia (13%), anorexia (16%), esophagitis (16%) and hyponatremia (16%). Thirty patients (96.8%) underwent surgery. One patient received palliative chemotherapy because of appearance of lung metastasis during CRT. The completion rate of protocol treatment was 93.5% (29/31). There was one treatment-related death after surgery. Pathological complete response was achieved in 42% (13/30). CONCLUSION: Preoperative CRT with CF and elective lymph node irradiation showed an acceptable toxicity and promising activity especially in ESCC.

Detection of KK-LC-1 Protein, a Cancer/Testis Antigen, in Patients with Breast Cancer.

BACKGROUND: Kita-Kyushu lung cancer antigen-1 (KK-LC-1) is a cancer/testis antigen and predominant target for cancer immunotherapy. Its detection is only established based on gene expression. In this study, we established a monoclonal antibody against KK-LC-1 to detect its protein expression in formalin-fixed samples. MATERIALS AND METHODS: The monoclonal antibody against KK-LC-1 was evaluated and the detection of KK-LC-1 between gene expression and protein expression was compared in patients with breast cancer. The monoclonal antibody clone 34B3, which we established, stained testicular germ cells positively. RESULTS: The rates of detection of KK-LC-1 gene and protein expression were 11.8% and 52.9%, respectively. Protein expression was detected in all triple-negative breast cancer cases studied (n=8). Furthermore, KK-LC-1 was detected in all tumours without oestrogen receptor expression. CONCLUSION: This study indicated that KK-LC-1 expression was detected in breast cancer, especially in oestrogen receptor-negative subtypes.

Clofarabine exerts antileukemic activity against cytarabine-resistant B-cell precursor acute lymphoblastic leukemia with low deoxycytidine kinase expression.

Cytosine arabinoside (Ara-C) is one of the key drugs for the treatment of acute myeloid leukemia. It is also used for consolidation therapy of acute lymphoblastic leukemia (ALL). Ara-C is a deoxyadenosine analog and is phosphorylated to form cytosine arabinoside triphosphate (Ara-CTP) as an active form. In the first step of the metabolic pathway, Ara-C is phosphorylated to Ara-CMP by deoxycytidine kinase (DCK). However, the current cumulative evidence in the association of the Ara-C sensitivity in ALL appears inconclusive. We analyzed various cell lines for the possible involvement of DCK in the sensitivities of B-cell precursor ALL (BCP-ALL) to Ara-C. Higher DCK expression was associated with higher Ara-C sensitivity. DCK knockout by genome editing with a CRISPR-Cas9 system in an Ara-C-sensitive-ALL cell line induced marked resistance to Ara-C, but not to vincristine and daunorubicin, indicating the involvement of DCK expression in the Ara-C sensitivity of BCP-ALL. DCK gene silencing due to the hypermethylation of a CpG island and reduced DCK activity due to a nonsynonymous variant allele were not associated with Ara-C sensitivity. Clofarabine is a second-generation deoxyadenosine analog rationally synthesized to improve stability and reduce toxicity. The IC50 of clofarabine in 79 BCP-ALL cell lines was approximately 20 times lower than that of Ara-C. In contrast to Ara-C, although the knockout of DCK induced marked resistance to clofarabine, sensitivity to clofarabine was only marginally associated with DCK gene expression level, suggesting a possible efficacy of clofarabine for BCP-ALL that shows relative Ara-C resistance due to low DCK expression.

Regional evaluation of childhood acute lymphoblastic leukemia genetic susceptibility loci among Japanese.

Genome-wide association studies (GWAS) performed mostly in populations of European and Hispanic ancestry have confirmed an inherited genetic basis for childhood acute lymphoblastic leukemia (ALL), but these associations are less clear in other races/ethnicities. DNA samples from ALL patients (aged 0-19 years) previously enrolled onto a Tokyo Children's Cancer Study Group trial were collected during 2013-2015, and underwent single nucleotide polymorphism (SNP) microarray genotyping resulting in 527 B-cell ALL for analysis. Cases and control data for 3,882 samples from the Nagahama Study Group and Aichi Cancer Center Study were combined, and association analyses across 10 previous GWAS-identified regions were performed after targeted SNP imputation. Linkage disequilibrium (LD) patterns in Japanese and other populations were evaluated using the varLD score based on 1000 Genomes data. Risk associations for ARID5B (rs10821936, OR = 1.84, P = 6 × 10-17) and PIP4K2A (rs7088318, OR = 0.76, P = 2 × 10-4) directly transferred to Japanese, and the IKZF1 association was detected by an alternate SNP (rs1451367, OR = 1.52, P = 2 × 10-6). Marked regional LD differences between Japanese and Europeans was observed for most of the remaining loci for which associations did not transfer, including CEBPE, CDKN2A, CDKN2B, and ELK3. This study represents a first step towards characterizing the role of genetic susceptibility in childhood ALL risk in Japanese.