Platinum-Based Compounds Induce Expression of p73 and Restores Drug- Sensitivity in p53 Dysfunctional Chronic Lymphocytic Leukemia (CLL) Cells.

Chronic lymphocytic leukemia (CLL) cells can lose function of P53 and acquire resistance to standard chemotherapy. We found that expression P73, a member of the P53 family, could be induced in CLL cells following CD40-ligation via a c-abl dependent pathway. Induced expression of P73 was associated with re-acquired sensitivity to drugs commonly used treat this disease, such as Fludarabine monophosphate. Similar effects also were noted for CLL cells transduced with an adenovirus vector encoding P731. Prior studies found that P73 also can be induced in breast and colon cancer cell lines following treatment with platinum-based compounds, potentially accounting for the activity of this class of drugs. We hypothesized that treatment of CLL cells with such compound also could induce P73 and that such induced expression also might be associated with re-acquired sensitivity of P53-deficient CLL cells to standard anti-cancer drugs. We studied the mechanisms and effects of platinum-based compounds on CLL cells lacking functional p53. Studies were done with both the p3 dysfunctional pro-lymphocytic celline MEC-1 and with primary CLL cells that lacked functional P53. Treatment of MEC-1 cells with cisplatinum or oxaliplatin induced nuclear translocation of c-Abl in several hours, which was subsequently followed by expression of P73, and then its putative target genes, encoding Bid, p21 and Fas (CD95). Platinum-induced expression of these P73-target genes could be inhibited by co-treatment of the cells with the c-Abl inhibitor imatinib. Cisplatinum treatment of MEC-1 cells resulted in cell cycle arrest. Furthermore, cis-platinum treatment of MEC-1 cells or P53-deficient CLL cells synergized with Fas-mediated apoptosis, and importantly resulted in acquired sensitivity to the drug fludarabine monophosphate in vitro, apparently via a c-Abl dependent pathway. Purified p53 dysfunctional CLL cells obtained before and after 24 and 48 hrs of in vivo cisplatinum treatment revealed de novo expression of both P73 and Bid, illustrating induction of P73 at therapeutic dosages of cisplatin. This study indicates that platinum treatment of CLL cells induces c-Abl dependent expression of P73, which can enhance the sensitivity of P53-deficient CLL cells to drugs such as fludarabine monophosphate. These results provide additional incentive to investigate the activity of platinum-based chemotherapy regimens in patients with refractory disease who have CLL cells lacking functional P53, which currently are ongoing in Europe and the United States.

An International Multicentric Trial with Fludarabine Plus Cyclosphosphamide in B-Cell Chronic Lymphocytic Leukemia (CLL) “Up Front”: Second Interim Analysis.

Introduction: On August 2002 an international multicentric trial on Fludarabine monophosphate (FAMP) plus Cyclophsphamyde (Cy) among previously untreated B-cell CLL, was activated. Our aim is to evaluate efficacy and toxicity of FAMP plus Cy in previously untreated B-cell CLL patients (pts). This is the second interim analysis after a fourth-year period. Material and Methods: Treatment consists in three consecutive days of oral FAMP 40 mg/m2 (n=84) or i.v. FAMP 25 mg/m2 (n=13) plus i.v. Cy 600 mg/m2 on day 1 or Cy 250 mg/m2 from day 1 to 3, every 28 days × 6 cycles. Responses were assessed according to the National Cancer Institute working group criteria after cycle 3 and again after cycle 6. Since August 2002 to March 2006, 109 CLL pts from Argentina (n=95), Perú (n=11) and Uruguay (n=3) were enrolled for this protocol; eighty-nine were evaluated for response and toxicity. Median age: 64 years old (range: 44–81); male = 47, female = 42; Binet staging: A=14, B=45, C=30; median beta-2 microglobuline = 4.00 mg/dL (range: 1.3–9.2); median LDH = 341 UI/L (range: 101–762); among patients with available data the CD 38 expression more than 10% was 38% (22 of 58 pts). Blood counts at inclusion: median values (range); Lymphocytes: 32 ×109/L (2,7–137), Hb: 120 g/L (50–164), platelets: 175×109/L (10–364). Renal and hepatic parameters within normal range limits. Cytogenetic by banding was available in 27 cases: no alterations (n=17), +12 (n=1), del (6), del (12) (n=1), lost Y (n=1). Results: At the time of this second interim analysis (March 2006), 56.2% (50 pts) had completed 6 cycles and 97.8% (87 pts) had undergone at least 3 cycles. Overall responses: 92% = 81 pts (CR: 39% = 35 pts; PR: 52% = 46 pts); treatment failure: 9% = 7 pts. Evaluation for toxicity: 89 episodes of haematological toxicity and 7 episodes of infection grade 3–4 were reported after 436 cycles. Thirteen pts died: seven due infectious complications because of prolonged hematologic toxicity; one due to tumoral lysis syndrome, one due hemoptysis associated with lung cancer and the remaining four due disease progression. At 24 months, estimated DFS was 70% (figure 1, SE 7.6%) and estimated Overall Survival was 76% (figure 2, SE 7.4%). The median survival was not achieved in responders (PR and CR). Conclusion: FAMP plus Cy combination as front-line treatment is effective in B-cell CLL. Haematologic toxicity is the most severe adverse events. The response rates to this therapy is quite similar to those reported for other multicentric trials and better than others GATLA protocols. Figure 1 Figure 1. Figure 2 Figure 2.