Comparison of variants in TPMT and NUDT15 between sequencing and genotyping methods in a multistate pediatric institution.

The risk of severe adverse events related to thiopurine therapy can be reduced by personalizing dosing based on TPMT and NUDT15 genetic polymorphisms. However, the optimal genetic testing platform has not yet been established. In this study, we report on the TPMT and NUDT15 genotypes and phenotypes generated from 320 patients from a multicenter pediatric healthcare system using both Sanger sequencing and polymerase chain reaction genotyping (hereafter: genotyping) methods to determine the appropriateness of genotyping in our patient population. Sanger sequencing identified variant TPMT alleles including *3A (8, 3.2% of alleles), *3C (4, 1.6%), and *2 (1, 0.4%), and NUDT15 alleles including *2 (5, 3.6%) and *3 (1, 0.7%). For genotyped patients, variants identified in TPMT included *3A (12, 3.1%), *3C (4, 1%), *2 (2, 0.5%), and *8 (1, 0.25%), whereas NUDT15 included *4 (2, 1.9%) and *2 or *3 (1, 1%). Between Sanger sequencing and genotyping, no significant difference in allele, genotype, or phenotype frequency was identified for either TPMT or NUDT15. All patients who were tested using Sanger sequencing would have been accurately phenotyped for either TPMT (124/124), NUDT15 (69/69), or both genes (68/68) if they were assayed using the genotyping method. Considering 193 total TPMT and NUDT15 Sanger Sequencing tests reviewed, all tests would have resulted in an appropriate clinical recommendation if the test had instead been conducted using the comparison genotyping platforms. These results suggest that, in this study population, genotyping would be sufficient to provide accurate phenotype calls and clinical recommendations.

The morbidity of open tumor biopsy for intraabdominal neoplasms in pediatric patients.

PURPOSE: Tumor biopsy is often essential for diagnosis and management of intraabdominal neoplasms found in children. Open surgical biopsy is the traditional approach used to obtain an adequate tissue sample to guide further therapy, but image-guided percutaneous core-needle biopsy is being used more often due to concerns about the morbidity of open biopsy. We used a national database to evaluate the morbidity associated with open intraabdominal tumor biopsy. METHODS: We identified all patients undergoing laparotomy with tumor biopsy in the National Surgical Quality Improvement Project-Pediatric (NSQIP-P) database from 2012 to 2018 and measured the frequency of complications in the 30 days postoperatively. We tested associations between patient characteristics and outcomes to identify risk factors for complications. RESULTS: We identified 454 patients undergoing laparotomy for biopsy of an intraabdominal neoplasm. Median postoperative hospital stay was 7 days (IQR 4-12) and operative time was 117 min (IQR 84-172). The overall complication rate was 12.1%, with post-operative infection (6%) and bleeding (4.2%) being the most common complications. Several patient characteristics were associated with bleeding, but the only significant association on multivariable analysis was underlying hematologic disorder. CONCLUSION: Open abdominal surgery for pediatric intraabdominal tumor biopsy is accompanied by significant morbidity. Postoperative infection was the most common complication, which can delay initiation of further therapy, especially chemotherapy. These findings support the need to prospectively compare percutaneous image-guided core-needle biopsy to open biopsy as a way to minimize risk and optimize outcomes for this vulnerable population.

Vorinostat Enhances Cytotoxicity of SN-38 and Temozolomide in Ewing Sarcoma Cells and Activates STAT3/AKT/MAPK Pathways.

Histone deacetylase inhibitors (HDACi) have been evaluated in patients with Ewing sarcoma (EWS) but demonstrated limited activity. To better understand the potential for HDACi in EWS, we evaluated the combination of the HDACi vorinostat, with DNA damaging agents SN-38 (the active metabolite of irinotecan and topoisomerase 1 inhibitor) plus the alkylating agent temozolomide (ST). Drugs were evaluated in sequential and simultaneous combinations in two EWS cell lines. Results demonstrate that cell viability, DNA damage and reactive oxygen species (ROS) production are dependent on the sequence of drug administration. Enhanced cytotoxicity is exhibited in vitro in EWS cell lines treated with ST administered before vorinostat, which was modestly higher than concomitant treatment and superior to vorinostat administered before ST. Drug combinations downregulate cyclin D1 to induce G0/G1 arrest and promote apoptosis by cleavage of caspase-3 and PARP. When ST is administered before or concomitantly with vorinostat there is activation of STAT3, MAPK and the p53 pathway. In contrast, when vorinostat is administered before ST, there is DNA repair, increased AKT phosphorylation and reduced H2B acetylation. Inhibition of AKT using the small molecule inhibitor MK-2206 did not restore H2B acetylation. Combining ST with the dual ALK and IGF-1R inhibitor, AZD3463 simultaneously inhibited STAT3 and AKT to enhance the cytotoxic effects of ST and further reduce cell growth suggesting that STAT3 and AKT activation were in part mediated by ALK and IGF-1R signaling. In summary, potent antiproliferative and proapoptotic activity were demonstrated for ST induced DNA damage before or simultaneous with HDAC inhibition and cell death was mediated through the p53 pathway. These observations may aid in designing new protocols for treating pediatric patients with high-risk EWS.