Hematopoietic stem cell (HSC) homing is believed to rely heavily on adhesion interactions between stem cells and stroma. An in vitro assay was developed for adhesion of engraftable HSCs in bone marrow suspensions to pre-established Dextertype long-term bone marrow culture stromal layers. The cell numbers in the adherent layer and supernatant were examined, along with the engraftment capability of adherent layer cells to indicate the number of HSCs that homed to in vitro stroma. The cell number in the supernatant declined over the 24-hour period. The number of test cells adhering to the stromal layer increased during the first hour and then fell at 6 and 24 hours. The number of test HSCs adhering to the stromal layer was substantial at 20 minutes, increased during the first hour, and then remained constant at 1, 6, and 24 hours of adhesion. These data indicate that adhesion of engraftable HSCs occurs quickly and increases during the first hour of contact with pre-established stroma, that adhesion plateaus within 1 hour of contact, and that HSCs maintain their engraftment capability for at least 24 hours of stromal adhesion. Long-term engraftment from test cells at more than 1 hour of adhesion represents 70.7% of the predicted engraftment from equivalent numbers of unmanipulated marrow cells, indicating that 2 of 3 test engraftable HSCs adhered. These findings demonstrate the usefulness of this model system for studying stemstromal adhesion, allowing further dissection of the mechanism of HSC homing and exploration of possible manipulations of the process. IntroductionHematopoietic stem cell (HSC) homing is the process by which HSCs, infused intravenously in the transplantation setting, specifically extravasate in the bone marrow to engraft and proliferate there. Homing has been studied extensively both in vivo and in vitro and is believed to rely on adhesion molecule interactions between stromata, which consist of stromal cells and extracellular matrix, and stem cells. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] In vivo homing studies typically rely on infusion of a labeled or detectable HSC population and subsequent detection at various times after the transplantation. 16,19 In this approach, the recipients must be examined early enough (approximately 24 hours or earlier) that only infused cells, and not their progeny, are detected. However, testing this early can make it difficult to ascertain that the cells are truly homed and not migratory. Also, to dissect the mechanisms of homing, it would be desirable to conduct various manipulations, such as adding an adhesion receptor blocking antibody, and this can be cumbersome or even impossible in vivo. On the other hand, in vitro systems are relatively easy to manipulate, but the assay result can be difficult to interpret. Most in vitro homing studies examine adhesion of a hematopoietic cell population or cell line to a test substrate, such as purified extracellular matrix molecule coatings or stromal cell lines, under various conditions. 20-29 ...

The toxic effects of sulfur mustard have been attributed to DNA modification with the formation of 7-hydroxyethylthioethyl guanine, 3-hydroxyethylthioethyl adenine and the cross-link, di-(2-guanin-7-yl-ethyl)sulfide. To investigate the action of bacterial 3-methyladenine DNA glycosylase II (Gly II) on these adducts, calf thymus DNA was modified with [14C]sulfur mustard and used as a substrate for Gly II. Gly II releases both 3-hydroxyethylthioethyl adenine and 7-hydroxyethylthioethyl guanine from this substrate. In comparison with the activity of Gly II towards methylated DNA, 3-hydroxyethylthioethyl adenine is released somewhat more slowly than 3-methyladenine, while 7-hydroxyethylthioethyl guanine is released much more readily than 7-methylguanine. Glycosylase action may play a role in protecting cells from the toxic effects of sulfur mustard.

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6064 Background: Juvenile granulosa cell tumors (JGCT) are rare sex cord-stromal tumors which occur primarily in children and adolescents. Methods: All individuals or proxy caregivers provided informed consent/assent for participation in the International OTST Registry. Clinical data was collected. When available, pathology was centrally reviewed. Staging was evaluated using the International Federation of Gynecology and Obstetrics (FIGO) classification. Kaplan-Meier survival analyses and exact permutation tests were performed. Results: Forty-two individuals with ovarian JGCT were enrolled. Median age at diagnosis was 9 years (range 0-27). Most individuals had Stage I disease (Stage Ia=16; Stage Ib=1; Stage Ic=16). Seven individuals presented with higher stage (Stage II=2; Stage III=5). Stage was unknown for 2 individuals. Three-year overall survival (OS) was 88% (CI 77%, 100%) and event-free survival (EFS) was 69% (CI 54%, 88%). At median follow-up time of 25 months (range 0-416), 9 patients (Stage Ia=1, Stage Ic=5, Stage III=3) had recurrent disease. Use of post-operative adjuvant chemotherapy varied by stage and timing of rupture. Of those with Stage Ic JGCT, 2/7 with preoperative rupture and 3/9 with intraoperative rupture recurred. Among individuals with recurrence, median time to recurrence was 11.5 months (range 3-19). Four of 9 individuals with recurrence survived (no evidence of disease n=2; alive with disease n=2). All individuals who died presented with extrapelvic recurrence. Median time from recurrence to death was 10 months (range 2-53). In individuals with recurrence, advanced stage at diagnosis (HR 5.1; p-value 0.087) and recurrence outside the tumor bed (HR Infinity; p-value 0.048) were associated with inferior OS. Three-year OS for individuals with recurrence was 57% (CI 30%, 100%). Conclusions: Low stage JGCT is associated with a favorable prognosis, however, recurrence is associated with lower survival rate. Within this series, recurrences presented within 2 years of diagnosis. Novel strategies are needed to address recurrent and extrapelvic disease.