Expression of the human concentrative nucleotide transporter 1 (hCNT1) gene correlates with clinical response in patients affected by Waldenström's Macroglobulinemia (WM) and small lymphocytic lymphoma (SLL) undergoing a combination treatment with 2-chloro-2'-deoxyadenosine (2-CdA) and Rituximab

PURPOSE

Resistance to nucleoside analogues agents is likely to be multifactorial and could involve a number of mechanisms affecting drug penetration, metabolism and targeting. In vitro studies of resistant human cell lines have confirmed that human concentrative nucleoside transporter 1 (hCNT1)-deficient cells display resistance.

EXPERIMENTAL DESIGN

We applied real-time PCR method to assess the mRNA expression of equilibrative and concentrative nucleoside transporter (hENT1, hCNT1), deoxycytidine and deoxyguanosine kinase (dCK, dGK), 5'-nucleotidase (5'-NT), ribonucleotide reductase catalytic and regulatory (RR1, RR2) subunits in bone marrow cells from 32 patients with Waldenström's Macroglobulinemia (WM) and small lymphocytic lymphoma (SLL) who received 2CdA-based chemotherapy. Responses to chemotherapy, were then correlated to the expression of these markers.

RESULTS

All 32 patients enrolled expressed lower levels of hCNT1 as compared to healthy donors. In univariate analysis, lower expression level of hCNT1 (p=0.0021) and RR2 (p=0.02) correlated with response to chemotherapy. In particular, patients with low levels of hCNT1 achieved inferior clinical response. No significant correlation between these genes expression and age, stage of disease was found. This study suggests that nucleotidase expression levels can be used to identify subgroups of WM and SLL patients who will likely respond differently to a 2CdA-based therapy.

Phase II trial of cladribine (2-CdA) and rituximab in patients with CLL and SLL: Preliminary report of a single institution

7093

Background: Byrd et al (Blood 2003) confirmed the synergistic effect of Rituximab and Fludarabine in the treatment of CLL patients (pts). The choice of purine analogue still remains controversial. We evaluated feasibility, efficacy, and toxicity of 2-CdA-Rituximab combination in the treatment of CLL and SLL pts requiring treatment. Methods: The combination therapy consisted of intravenous Rituximab at a dose of 375 mg/m2 on Day 1 and 2-CdA at a dose of 0.1 mg/kg (sc injection) per day on Days 2 through 6. The course was repeated at 4-week intervals for 4 times. 31 pts (21 CLL and 10 SLL) was enrolled in the study and the median age was 59 years (31–73); 42% of pts were pre-treated. A CT scan was abnormal in 95% of CLL pts. Immunophenotypic evaluation by ZAP-70 was positive in 70% of pts while no evaluable pts showed an adverse prognostic cytogenetic features by FISH. Minimal residual disease (MRD) assessment was performed by flow-cytometry and PCR methods. Results: 2 pts had to discontinue therapy after 2 cycle: one due to herpes zoster reactivation and the other one to the progression disease (PD). We observed grade 3 and 4 neutropenia in 4 pts (12%), major infections in 4 pts (12%) and no episodes of grade 3–4 thrombocytopenia. 24 pts were evaluable for response with an ORR of 96%. At the end of therapy 10 pts (42%), 7 CLL and 3 SLL, achieved a CR, with negative MRD (by PCR) in 4 pts (3 untreated); 13 pts (54%) obtained a PR and 1 patient had no response. With a median follow-up of 12 months (range 3–34) 7 pts (2 pts with MRD+CR and 5 pts with PR after treatment) experimented a PD; 5 of these pts were pre-treated and 2 died because of PD. Conclusions: The combination of 2- CDA and Rituximab seems to be tolerable and active principally for untreated pts and able to induce a molecular clearance also in pre-treated pts. The achieving of a CR with negative MRD seems to be the most important issue to improve the outcome.

No significant financial relationships to disclose.

hCNT1 in Waldenström’s macroglobulinemia (WM) and small lymphocytic lymphoma (SLL) patients (pts): A possible predictive biomarker of 2-chloro-2`-deoxyadenosine (2-CDA) clinical activity

13087

Background: The resistance mechanism to 2-CDA is not completely known. In this study we used pharmacogenomic to identify genetic factors that influence drug response and to better investigate 2-CDA complex intracellular metabolism. Methods: Using Real-time PCR method (ABI-PRISM 7000 machine) we amplified seven genes, encoding for equilibrative and concentrative nucleoside transporter (hENT1, hCNT1), deoxycytidine and deoxyguanosine kinase (dCK, dGK), 5`-nucleotidase (5`NT), ribonucleotide reductase catalytic and regulatory (RR1, RR2) subunits, in bone marrow (BM) at baseline of 17 pts with WM or SLL in order to verify the correlation between gene expression and clinical outcome. All pts were treated with a combination therapy (2-CDA 0.1 mg/kg sc injection and Rituximab at standard schedule). Quantitation was performed using the Delta CT calculation: the value of gene expression was normalised to the calibrator (healthy tissue cells). Results: hCNT1 and 5’NT gene expression analysis has shown lower values in pts than in controls. The other markers didn’t show any significance. Two pts achieving partial remission (PR) presented 100 times lower hCNT1 levels (median 6.8*10−4, range 6.8–6.9*10−4) than pts (n = 10) in complete remission (median 7.9*10−2, range 0.1–4.6*10−1; p = 0.03). Conclusions: hCNT1 seems to be the most important gene involved in 2-CDA clinical activity and its expression may correlate with prognosis. Compared to controls, the low plasmatic RNA level of hCNT1 exhibited by our pts doesn’t seem to be predictive of lack of clinical activity of 2-CDA. However the lower level of hCNT1 plasmatic expression detected in the two pts who achieved only PR could suggest a possible relationship between reduced hCNT1 plasmatic expression and a diminished clinical activity of 2-CDA. Thus it might be important to explore the possibility of standardizing a quantitative method in order to identify a threshold value which could be predictive of drug resistance.

No significant financial relationships to disclose.