No abstract

Desmoplastic small round cell tumor (DSRCT) is an extremely rare and aggressive neoplasm, which mainly affects young males and generally presents as a widely disseminated tumor within the peritoneal cavity. Due to the rarity of the tumor, its younger and overall healthier patient population (compared with other tumor types) and the fact that it lacks definitive histological and immunohistological features, the diagnosis of DSRCT may be frequently delayed or the tumor may be entirely misdiagnosed as a different type of abdominal sarcoma. The present study aimed to rectify the lack of models that exist for this rare neoplasm, through the development of several DSRCT tissue cultures and xenograft lines. Samples were received from surgeries and biopsies from patients worldwide and were immediately processed for xenograft development in nude mice. Tumor tissues were minced and fragments were injected into the dorsal flanks of nude mice. Of the 14 samples received, nine were established into xenograft lines and five into tissue culture lines. Xenografts displayed the microscopic histology of their parent tumors and demonstrated two different growth rates among the established xenograft lines. Overall, the establishment of these xenograft and tissue culture lines provides researchers with tools to evaluate DSRCT responses to chemotherapy and to investigate DSRCT-specific signaling pathways or mechanisms.

There are several indications of a possible physiological role for 4-hydroxyestradiol (4-OHE 2 ) in hormone-responsive tissues. To examine a hormonal activity of 4-OHE 2 , we have studied the binding of 3 H-labeled 4-OHE 2 to mouse uterine cytosolic protein. In uteri of 3-week-old mice, total binding was 319·4 13·9 fmol/mg protein. Binding in the presence of excess unlabeled 4-OHE 2 dropped to 82·1 1·7 fmol/mg protein, whereas 214·6 9·4 fmol/mg protein bound while incubating in an excess of unlabeled 17 -estradiol (E 2 ). The difference between the two binding values in the presence of excess steroid (132·5 11·1 fmol/mg protein) is taken as selective binding of 4-OHE 2 to a specific protein. In mice older than 4 weeks, the specific 4-OHE 2 binding declined: 32·0 4·0 fmol/mg protein at 8 weeks, 54·8 6·3 fmol/mg protein at 12 weeks and 54·6 5·2 fmol/mg protein at 9 months. Of other organs tested (liver, kidney, lung and whole brain) only lung showed significant selective binding of 4-OHE 2 . When E 2 -binding sites are blocked, 4-OHE 2 binding follows first-order kinetics, yielding a dissociation constant (K d ) value of 11·8 2·1 nM. The specific binding of 4-OHE 2 was not inhibited by any other steroids or estrogen metabolites that were tested, except for 2-hydroxyestradiol (2-OHE 2 ), which displayed competitive inhibition of 4-OHE 2 binding with an inhibition constant (K i ) value of 98·2 12·6 nM. These results lead us to conclude that 4-OHE 2 binds to a specific binding protein, distinct and different from binding to estrogen receptors (ER and ER ). The physiological role of this binding remains to be elucidated.

Desmoplastic small round cell tumor (DSRCT) is an extremely rare and aggressive neoplasm which mainly affects young males and generally presents as a widely disseminated tumor within the peritoneal cavity. Due to the rarity of the tumor, a younger and overall healthier patient population, and because it lacks definitive histologic and immunohistologic features, it is possible that DSRCT is frequently delayed in diagnosis or is entirely misdiagnosed as a different kind of abdominal sarcoma. This study seeks to rectify the dearth of models that exist for this rare neoplasm through the development of several DSRCT tissue culture and xenograft lines. Samples were received from surgeries and biopsies from patients around the world and were immediately processed for xenograft development in nude mice. Tumor tissues were minced and fragments were injected onto the dorsal flank of nude mice. Of the 15 samples received, 9 were established into xenograft lines and 6 of those into tissue culture lines. Xenografts displayed the microscopic histology of their parent tumors and two different growth rates among established xenograft lines. Chemosensitivity of tumors was assessed against a variety of chemotherapeutic agents and IC50 values established for each drug and cell line. Interestingly, the cell lines were split into two distinct groups in terms of morphology, growth rate and chemosensitivity. Overall, the establishment of these xenograft and tissue culture lines gives researchers tools to evaluate DSRCT response to chemotherapy and investigate DSRCT-specific signaling pathways or mechanisms. Citation Format: Constantine SA Markides, Dana M. Vardeman, Linh Luong, Douglas R. Coil, Anthony Kozielski, John Mendoza, Beppino C. Giovanella. DSRCT: Establishing xenograft and tissue culture cell lines and assessing chemosensitivity. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2769. doi:10.1158/1538-7445.AM2013-2769

2578 Background: CZ48, the 20-O-propionate ester of camptothecin (CPT), is a prodrug of CPT first described by Cao et al. in 1998. The side-chain is enzymatically cleaved in tissues. This gives rise to CPT, a potent inhibitor of topoisomerase I. Methods: An open-label, single-arm, dose-escalation Phase I study was performed to determine the maximum tolerated dose (MTD) of CZ48 in patients with advanced solid tumors. Initial dosing started qd po 80mg/m2, advancing to 2560mg/m2 for 21 consecutive days, followed by 7 days rest. Dosing was restarted in cohorts of 3 patients tid po at 18mg/m2 and escalated to 1g/m2on a 5 days on, 2 days off schedule for 28 days. Patients were prescreened by measuring CPT levels in plasma following a single pilot dose of CZ48. Dose was doubled until occurrence of at least Grade 2 adverse event, at which time 3+3 patient cohorts with a dose escalation of 33%-100% were implemented. DLT in 2/6 patients defined the MTD as the preceding DLT dose. PK parameters were measured prior to dosing, days 1-5, and day 28 of Cycle 1. Results: Poor absorption led to initial qd dosing reaching 2560mg/m2 with no signs of DLT. Subsequent tid dosing showed improved plasma levels and arrival at DLT. 34 patients were treated across 8 dose levels from 18 to 1000 mg/m2. The most frequent study-related adverse effects were cystitis, vomiting, diarrhea and fatigue. Grade IV toxicities observed were febrile neutropenia, anemia, and thrombocytopenia. Preliminary PK data in the qd dosing showed poor correlation between dose and Cmax or AUC, while PK in tid patients showed slightly improved correlation between dose and both CZ48 AUC (Pearson's correlation coefficient ϱ=0.476, p<0.01) and CZ48 Cmax(ϱ =0.51, p<0.01). Evidence of clinical activity with stable disease ≥ 6 months was observed in 2 heavily pre-treated colon and one breast cancer patient. Conclusions: The MTD of tid po CZ48 administered 5 days on, 2 days off of 28-day cycle is between 750 mg/m2 and 576 mg/m2. Overall toxicity is relatively mild, with DLT being cystitis and myelosuppression. Even with tid dosing, PK values correlate poorly to dose. A new formulation with 3-5 fold higher preclinical absorption values is being considered for introduction into the trial. Clinical trial information: NCT00947739.