No abstract

The breast cancer tumor-suppressor gene, BRCA1, encodes a protein with a BRCT domain-a motif that is found in many proteins that are implicated in DNA damage response and in genome stability. Phosphorylation of BRCA1 by the DNA damage-response proteins ATM, ATR and hCds1/Chk2 changes in response to DNA damage and at replication-block checkpoints. Although cells that lack BRCA1 have an abnormal response to DNA damage, the exact role of BRCA1 in this process has remained unclear. Here we show that BRCA1 is essential for activating the Chk1 kinase that regulates DNA damage-induced G2/M arrest. Thus, BRCA1 controls the expression, phosphorylation and cellular localization of Cdc25C and Cdc2/cyclin B kinase-proteins that are crucial for the G2/M transition. We show that BRCA1 regulates the expression of both Wee1 kinase, an inhibitor of Cdc2/cyclin B kinase, and the 14-3-3 family of proteins that sequesters phosphorylated Cdc25C and Cdc2/cyclin B kinase in the cytoplasm. We conclude that BRCA1 regulates key effectors that control the G2/M checkpoint and is therefore involved in regulating the onset of mitosis.

In the management of stage I and II breast cancer, breast conservation with lumpectomy and radiation offers results at 10 years that are equivalent to those with mastectomy.

No abstract

Cyclophosphamide (Cy) is a potent immunosuppressive agent that is selectively toxic to lymphocytes proliferating in response to recent antigen stimulation. In animal models, both graft rejection and GVHD after histoincompatible BMT can be inhibited by the posttransplantation administration of high-dose Cy. Therefore, a phase I clinical trial was undertaken to determine the minimal conditioning, including posttransplantation Cy, that permits the stable engraftment of partially HLA-mismatched marrow (up to 3 HLA antigens) from first-degree relatives. Thirteen patients (median age, 53 years) with high-risk hematologic malignancies received conditioning with fludarabine, 30 mg/m2 per day from days -6 to -2, and TBI, 2 Gy on day -1. All patients received Cy, 50 mg/kg on day 3, mycophenolate mofetil from day 4 to day 35, and tacrolimus from day 4 to day > or = 50. Three patients in cohort 1 received no additional conditioning, and 2 experienced graft rejection. Ten patients in cohort 2 received identical conditioning with the addition of Cy 14.5 mg/kg on days -6 and -5. Sustained donor cell engraftment occurred in 8 of these patients, with a median time to absolute neutrophil count > 500/microL of 15 days (range, 13-16 days) and to unsupported platelet count > 20,000/microL of 14 days (range, 0-26 days). All patients with engraftment achieved > or = 95% donor chimerism within 60 days of transplantation. Two patients with myelodysplastic syndrome rejected their grafts but experienced autologous neutrophil recovery at 24 and 44 days. Histologic acute GVHD developed in 6 patients (grade II in 3 patients, grade III in 3 patients) at a median of 99 days (range, 38-143 days) after transplantation and was fatal in 1 patient. At a median follow-up of 191 days (range, 124-423 days), 6 of 10 patients in cohort 2 were alive, and 5 were in complete remission of their disease, including both patients with graft rejection. These data demonstrate that partially HLA-mismatched bone marrow can engraft rapidly and stably after nonmyeloablative conditioning that includes posttransplantation Cy. Clinically significant antitumor responses occur, even among patients who reject their donor grafts.

The breast and ovarian cancer susceptibility gene product BRCA1 has been reported to be expressed in a cell cycle-dependent manner; possess transcriptional activity; associate with several proteins, including the p53 tumor suppressor; and play an integral role in certain types of DNA repair. We show here that ectopic expression of BRCA1 using an adenovirus vector (Ad-BRCA1) leads to dephosphorylation of the retinoblastoma protein accompanied by a decrease in cyclin-dependent kinase activity. Flow cytometric analysis on Ad-BRCA1-infected cells revealed a G 1 or G 2 phase accumulation. High density cDNA array screening of colon, lung, and breast cancer cells identified several genes affected by BRCA1 expression in a p53-independent manner, including DNA damage response genes and genes involved in cell cycle control. Notable changes included induction of the GADD45 and GADD153 genes and a reduction in cyclin B1 expression. Therefore, BRCA1 has the potential to modulate the expression of genes and function of proteins involved in cell cycle control and DNA damage response pathways.

R115777 is bioavailable after oral administration and has an acceptable toxicity profile. Based upon pharmacokinetic data, the recommended dose for phase II trials is 500 mg orally bid (total daily dose, 1, 000 mg) for 5 consecutive days followed by 9 days of rest. Studies of continuous dosing and studies of R115777 in combination with chemotherapy are ongoing.

No abstract