Incidence and prognostic impact of other cancers in a population of long-term survivors of chronic lymphocytic leukemia.

BACKGROUND: Information on the impact of other cancers (OCs) in long-term survivors (LTSs) of chronic lymphocytic leukemia (CLL) is limited. PATIENTS AND METHODS: Patients with CLL who survived >10 years were defined as LTSs of CLL. We calculated standardized incidence ratios (SIRs) to compare the incidence of OC in LTS of CLL versus the general population. A multivariable model was used to identify independent predictors of OC. Overall survival was analyzed as a function of the presence of OC. RESULTS: Among 797 LTSs of CLL, the cumulative frequency of OC was 36%, similar between 570 patients (72%) who required treatment for CLL (TRT) and 227 (28%) who remained untreated (UT). The most common OC in both groups was non-melanoma skin cancer, followed by prostate cancer, breast cancer, melanoma, lung cancer, and leukemia in TRT patients, and by prostate cancer, breast cancer, melanoma, lung cancer, and gastrointestinal tumors in the UT group. The SIR for all OC was 1.2 (P = 0.034). It was higher in males (SIR 1.31; P = 0.013) and patients <60 years (SIR 1.27; P = 0.027). A higher SIR was shown for secondary leukemia, melanoma, and head-and-neck cancers, whereas a lower SIR was found for gastrointestinal and bladder cancers. Independent predictors of OC development were advanced age, male gender, and lower platelets. The survival of patients with OC was 16.2 months and that of patients without OC 22.9 years. CONCLUSIONS: LTSs of CLL have an increased incidence of OC compared with the general population. CLL therapy is not a risk factor for OC in LTSs of CLL. The presence of an OC in these patients may be associated with shorter survival.

Pharmacodynamics and proteomic analysis of acalabrutinib therapy: similarity of on-target effects to ibrutinib and rationale for combination therapy.

Acalabrutinib, a highly selective Bruton's tyrosine kinase inhibitor, is associated with high overall response rates and durable remission in previously treated chronic lymphocytic leukemia (CLL); however, complete remissions were limited. To elucidate on-target and pharmacodynamic effects of acalabrutinib, we evaluated several laboratory endpoints, including proteomic changes, chemokine modulation and impact on cell migration. Pharmacological profiling of samples from acalabrutinib-treated CLL patients was used to identify strategies for achieving deeper responses, and to identify additive/synergistic combination regimens. Peripheral blood samples from 21 patients with relapsed/refractory CLL in acalabrutinib phase I (100-400 mg/day) and II (100 mg BID) clinical trials were collected prior to and on days 8 and 28 after treatment initiation and evaluated for plasma chemokines, reverse phase protein array, immunoblotting and pseudoemperipolesis. The on-target pharmacodynamic profile of acalabrutinib in CLL lymphocytes was comparable to ibrutinib in measures of acalabrutinib-mediated changes in CCL3/CCL4 chemokine production, migration assays and changes in B-cell receptor signaling pathway proteins and other downstream survival proteins. Among several CLL-targeted agents, venetoclax, when combined with acalabrutinib, showed optimal complementary activity in vitro, ex vivo and in vivo in TCL-1 adoptive transfer mouse model system of CLL. These findings support selective targeting and combinatorial potential of acalabrutinib.

Pretreatment of cytokinetics in acute myelogenous leukemia. Age-related prognostic implications.

To determine the clinical and biologic relevance of cellular kinetics in leukemia, DNA flow cytometric analysis was performed on bone marrow biopsy specimens from 148 previously untreated adult patients with acute myelogenous leukemia. The proportion of cells in synthesis, second growth, and mitosis (S + G2M) ranged from 4% to 33% with a median of 14%. The overall incidence of complete remission was not affected by the pretreatment cell cycle distribution. As in earlier studies, there was a marked decline in remission rate with advancing age from 73% for patients age less than or equal to 50 yr to 50% for those greater than 50 (P less than 0.01). Although not affecting remission induction overall, an increasing proportion of cells in S + G2M phase was favorable in patients under the age of 50 yr, but was associated with a progressive decline in remission rate in older patients (P = 0.01). This age-related divergent effect of cell cycle kinetics on initial response to therapy was confined to the less favorable subgroup of patients with karyotypic abnormalities, whereas patients with normal diploid cytogenetics had a consistently higher response rate regardless of proliferative activity. A positive correlation was also observed between percent of S + G2M cells and the proportion of diploid metaphases in young patients, contrasting with a negative correlation in the older age group. Our observations strongly suggest that the well-recognized prognostic effect of age on remission induction is not entirely host-mediated, but is at least partly an expression of disease-intrinsic differences between young and older patients.

High-dose caspofungin combination antifungal therapy in patients with hematologic malignancies and hematopoietic stem cell transplantation.

Pneumocandins have concentration-dependent antifungal activity and higher dose of caspofungin (HD-CAP) in combination with other licensed antifungal therapy (OLAT) may improve response. Thirty-four patients who received HD-CAP were compared with 63 patients who received standard dose (SD)-CAP. There were no differences between the groups in either patient or disease characteristics. Significantly more patients in the HD-CAP arm had extrapulmonary infections (29 vs 8% in SD group; P=0.0053), and non-Aspergillus species infection (21 vs 6%; P=0.05) and had received prior antifungal therapy (71 vs 33%; P=0.0004). No serious adverse reactions were noted in patients receiving HD- or SD-CAP therapy. Twelve weeks after treatment commenced 44% had a complete or partial response compared with 29% in SD-CAP group (P=0.1). Logistic regression analysis showed a significant probability of a favorable outcome at 12 weeks in patients who received HD-CAP (OR 3.066, 95% CI, 1.092-8.61; P=0.033). This may in part reflect higher number of patients in HD group had received granulocyte-macrophage colony-stimulating factor (41 vs 14% in SD group; P=0.04) and/or interferon gamma (26 vs 5% in SD group; P=0.003) immune enhancement. Further studies are needed to evaluate efficacy of HD-CAP in severely immunosuppressed cancer patients with invasive fungal infections.

Targeting Hsp90 by 17-AAG in leukemia cells: mechanisms for synergistic and antagonistic drug combinations with arsenic trioxide and Ara-C.

17-Allylamino-17-demethoxygeldanamycin (17-AAG) is a new anticancer agent currently in clinical trials. The ability of 17-AAG to abrogate the function of heat-shock protein Hsp90 and modulate cellular sensitivity to anticancer agents has prompted recent research to use this compound in drug combination therapy. Here we report that 17-AAG has striking opposite effects on the activity of arsenic trioxide (ATO) and ara-C. Combination of 17-AAG with ATO exhibited a synergistic effect in leukemia cells, whereas coincubation of 17-AAG and ara-C showed antagonistic activity. Mechanistic studies revealed that ATO exerted cytotoxic action by reactive oxygen species generation, and activated Akt survival pathway. 17-AAG abrogated Akt activation and enhanced the activity of ATO. In contrast, treatment of leukemia cells with 17-AAG caused a G1 arrest, a decrease in DNA synthesis and reduced ara-C incorporation into DNA, leading to antagonism. The ability of 17-AAG to enhance the antileukemia activity of ATO was further demonstrated in primary leukemia cells isolated from patients with acute myeloid leukemia and chronic lymphocytic leukemia, including cells from refractory patients. Our data suggest that combination of 17-AAG and ATO may be an effective therapeutic regimen. Caution should be exercised in using 17-AAG together with ara-C, as their combination effects are schedule dependent.

Phase I study of 506U78 administered on a consecutive 5-day schedule in children and adults with refractory hematologic malignancies.

PURPOSE: A phase I study was conducted to determine the maximum-tolerated dose (MTD), toxicity profile, and pharmacokinetics of a novel purine nucleoside, nelarabine, a soluble prodrug of 9-beta-D-arabinosylguanine (araG; Nelarabine), in pediatric and adult patients with refractory hematologic malignancies. PATIENTS AND METHODS: Between April 1994 and April 1997, 93 patients with refractory hematologic malignancies were treated with one to 16 cycles of study drug. Nelarabine was administered daily, as a 1-hour intravenous infusion for 5 consecutive days, every 21 to 28 days. First-cycle pharmacokinetic data, including plasma nelarabine and araG levels, were obtained on all patients treated. Intracellular phosphorylation of araG was studied in samples of leukemic blasts from selected patients. RESULTS: The MTDs were defined at 60 mg/kg/dose and 40 mg/kg/dose daily x 5 days in children and adults, respectively. Dose-limiting toxicity (DLT) was neurologic in both children and adults. Myelosuppression and other significant organ toxicities did not occur. Pharmacokinetic parameters were similar in children and adults. Accumulation of araGTP in leukemic blasts was correlated with cytotoxic activity. The overall response rate was 31%. Major responses were seen in patients with T-cell malignancies, with 54% of patients with T-lineage acute lymphoblastic leukemia achieving a complete or partial response after one to two courses of drug. CONCLUSION: Nelarabine is a novel nucleoside with significant cytotoxic activity against malignant T cells. DLT is neurologic. Phase II and III trials in patients with T-cell malignancies are encouraged.

Synergistic effect of targeting mTOR by rapamycin and depleting ATP by inhibition of glycolysis in lymphoma and leukemia cells.

The mammalian target of rapamycin (mTOR) pathway plays important roles in regulating nutrient metabolism and promoting the growth and survival of cancer cells, which exhibit increased glycolysis for ATP generation. In this study, we tested the hypothesis that inhibition of the mTOR pathway and glycolysis would synergistically impact the energy metabolism in cancer cells and may serve as an effective therapeutic strategy to kill malignant cells. Using human lymphoma cells and leukemia cells, we demonstrated that the combination of rapamycin, an mTOR inhibitor, with a glycolytic inhibitor produced synergistic cytotoxic effect, as evidenced by apoptosis and cell growth inhibition assays. Mechanistic studies showed that inhibition of the mTOR pathway by rapamycin alone sufficiently suppressed the phosphorylation of the downstream molecules p70S6K and 4E-BP-1, but only caused a moderate cytostatic effect. Combination of mTOR inhibition and blockage of glycolysis synergistically suppressed glucose uptake and severely depleted cellular ATP pools, leading to significant enhancement of cell killing. In contrast, combination of rapamycin and ara-C did not increase cytotoxicity in vitro. Our findings suggest that targeting mTOR pathway in combination with inhibition of glycolysis may be an effective therapeutic strategy for hematological malignancies. This mechanism-based drug combination warrants further investigation in preclinical and clinical settings.

Increased expression of CD152 (CTLA-4) by normal T lymphocytes in untreated patients with B-cell chronic lymphocytic leukemia.

Patients with chronic lymphocytic leukemia (CLL) have defects in both cellular and humoral immunity. Since CD152 (CTLA-4) plays a critical role in downregulating T-cell responses, we studied the expression of surface and cytoplasmic CD152 (sCD152 and cCD152, respectively) in freshly isolated T cells from treatment-naïve patients with CLL. CD4+ and CD8+ T cells from these patients demonstrated significantly increased sCD152 and cCD152 compared to normal donors. Furthermore, these patients had an increased proportion of the regulatory CD4(+)/CD25(+)/CD152+ subset that correlated with advanced Rai stage, unfavorable cytogenetics and low serum IgG and IgA levels. The expression of sCD152 by T cells also correlated with ZAP-70 expression by CLL B cells. The proportion of CD4(+)/CD25+ cells was also correlated with unmutated immunoglobulin heavy chain variable gene status. Blockade of CD152 with monoclonal antibody (mAb) in proliferation assays was associated with potent T-cell proliferation in response to autologous and allogeneic CD40-activated CLL B cells. In summary, T cells from patients with CLL may be primed for anergy by expressing increased amounts of CD152; anti-CD152 mAb may represent a therapeutic opportunity to enhance an immune response against autologous leukemia cells.

Fludarabine infusion potentiates arabinosylcytosine metabolism in lymphocytes of patients with chronic lymphocytic leukemia.

Our previous work has shown that incubation of K562 cells or lymphocytes from patients with advanced chronic lymphocytic leukemia (CLL) with arabinosyl-2-fluoroadenine (F-ara-A) potentiates the rate of arabinosylcytosine 5'-triphosphate (ara-CTP) synthesis during subsequent treatment with arabinosylcytosine (ara-C). To test the biochemical modulation of ara-CTP in a clinical setting, we designed a protocol to administer fludarabine (Fludara, F-ara-AMP) and ara-C in a pharmacologically directed sequence for patients with CLL refractory to conventional fludarabine therapy. ara-C was infused in seven patients with progressive CLL at a dose rate that maximizes ara-CTP accumulation (0.5 g/m2 during 2 h). Fludarabine (30 mg/m2 during 30 min) was infused 20 h later, followed by a second, identical dose of ara-C at 24 h, when the concentration of F-ara-A 5'-triphosphate (F-ara-ATP) was maximal in CLL cells. Comparison of ara-CTP pharmacokinetics in circulating CLL cells demonstrated that the ara-CTP area under the curve increased by a median of 1.5-fold (range, 1.1- to 1.7-fold) after fludarabine infusion. Plasma pharmacokinetics indicated that neither the median steady-state ara-C concentrations nor the levels of its deamination product arabinosyluracil were significantly affected by fludarabine infusion. The median rate of ara-CTP elimination was slightly faster after fludarabine treatment (t1/2, 6.7 versus 5.8 h), suggesting that catabolism of ara-CTP was not responsible for the increased ara-CTP area under the curve. The rate of ara-CTP accumulation by CLL cells after fludarabine infusion, however, was increased by a median of 1.3-fold in seven of the eight patients (range, 1.2- to 1.8-fold); the peak occurred within 1 h of the end of the infusion. In vitro incubation of leukemic lymphocytes with F-ara-A before ara-C also showed a median 1.3-fold increase in the rate of ara-CTP accumulation. Thus, infusion of fludarabine before ara-C augments ara-CTP metabolism in leukemic lymphocytes. This knowledge should be considered in the design of combination chemotherapy.

Quantitation of 1-beta-D-arabinofuranosylcytosine 5'-triphosphate in the leukemic cells from bone marrow and peripheral blood of patients receiving 1-beta-D-arabinofuranosylcytosine therapy.

A method for the detection and quantitation of 1-beta-D-arabinofuranosylcytosine 5'-triphosphate (ara-CTP), the active metabolite cells and leukemic cells of the peripheral blood from patients receiving ara-C therapy is described. ara-CTP is separated from normal cellular nucleotides by high-pressure liquid chromatography and is quantitated by its absorbance of ultraviolet light at 280 nm with a lower limit of sensitivity of 25 pmol/2 x 10(7) cell equivalents. During separate courses of continuous infusion of different therapeutic doses of ara-C, ara-CTP accumulated in the leukemic bone marrow cells of a patient with acute myelogenous leukemia in proportion to the dose of ara-C. Continuous infusion of ara-C (90 mg/sq m/day) resulted in plateau levels of ara-CPT in peripheral blast cells after 24 hr (115 pmol/1 x 10(7) cell equivalents). A priming dose of ara-C(125 to 250 mg/sq m) followed by a 1-hr infusion of an equal dose of ara-C to patients with acute myelogenous leukemia facilitated the determination of ara-CTP retention in bone marrow and peripheral blood leukemic cells in vivo. This procedure should be useful for extended studies of the biochemical pharmacology of ara-CTP in vivo.

Alterations in bone marrow and blood mononuclear cell polyamine and methylglyoxal bis(guanylhydrazone) levels: phase I evaluation of alpha-difluoromethylornithine and methylglyoxal bis(guanylhydrazone) treatment of human hematological malignancies.

Nine patients with hematological malignancies were treated with difluoromethylornithine and methylglyoxal bis(guanylhydrazone). The number of circulating blast cells decreased in all of the patients treated with DFMO and MGBG for longer than 1 wk. Morphological evidence of myeloid maturation was evident in four patients with leukemia and the circulating M Protein decreased in one patient with multiple myeloma. The polyamine content of the mononuclear cells in both the peripheral blood and bone marrow was transiently increased after the initial MGBG dose. During administration of DFMO decreases were achieved in the peripheral blood mononuclear cell putrescine levels in 7 patients, spermidine levels in 5 patients, and spermine levels in 4 patients. Alterations in bone marrow mononuclear cell polyamine levels were similar to those which occurred in the peripheral cells. An average of 9 days of DFMO treatment was required to lower mononuclear cell polyamine levels. Three of the 4 evaluable patients receiving multiple MGBG doses had an increased mononuclear cell content of MGBG after DFMO pretreatment. Enhancement of cellular MGBG levels was not directly correlated to the degree of cellular polyamine depletion.

Pharmacokinetics of [14C]methylglyoxal-bis-guanylhydrazone) in patients with leukemia.

Methylglyoxal-bis(guanylhydrazone) (MGBG; NSC 32946), a competitive inhibitor of S-adenosyl-L-methionine decarboxylase (EC 4.1.1.50), currently being reevaluated for its clinical antileukemic activity. MGBG labeled with 14C in the guanylhydrazone moiety was administered i.v. (150 microCi; specific activity, 1.9 microCi/mumol; 20 mg total) to six patients with leukemia. All patients in the study had normal renal and hepatic function. [14C]MGBG underwent no in vivo metabolism; it disappeared from the plasma with an average terminal t 1/2 of 4.1 hr. The 72-hr cumulative urinary excretion was only 14.5 +/- 2.2% (S.E.M.) of the total radioactive dose. The apparent volume of distribution was 661 ml/kg and the total clearance rate was 21.2 ml/kg/min. The low urinary excretion rate and the relatively rapid plasma clearance suggest that MGBG may be sequestered in the body. Therefore, if MGBG is administered by a frequent treatment schedule, the prolonged biological half-life in humans may significantly contribute to its clinical toxicity.

Modulation of 9-beta-D-arabinofuranosyladenine 5'-triphosphate and deoxyadenosine triphosphate in leukemic cells by 2'-deoxycoformycin during therapy with 9-beta-D-arabinofuranosyladenine.

The effect of the adenosine deaminase inhibitor, 2'-deoxycoformycin, on cellular nucleotides during therapy with continuous infusion of 9-beta-D-arabinofuranosyladenine (ara-A) has been investigated. In three courses of treatment using increasing doses, the active 5'-triphosphate of ara-A, 9-beta-D-arabinofuranosyladenine 5'-triphosphate (ara-ATP) accumulated in leukemic cells and erythrocytes from a patient treated for acute lymphocytic leukemia in proportion to the dose of ara-A. The cellular ara-ATP concentration increased more than 5-fold after the injection of a single, nontoxic, but pharmacologically active dose of 2'-deoxycoformycin 24 hr after initiation of ara-A infusion. However, this response was associated with a concomitant increase in the cellular deoxyadenosine triphosphate concentrations to levels equal to or greater than those of ara-ATP throughout the three treatment courses studied. Consistent with previous results using cell-free systems, it was demonstrated that a competitive relationship exists between deoxyadenosine triphosphate and ara-ATP for the inhibition of DNA synthesis in cultured human lymphoblastoid cells and that the ratio of the cellular concentrations of these nucleotides could predict the extent of inhibition of DNA synthesis. Application of this rationale to the nucleotides in the leukemic cells of the patient suggested that administration of 2'-deoxycoformycin may create a cellular biochemical milieu that could be antagonistic to the inhibition of DNA synthesis by ara-ATP.

Saturation of 1-beta-D-arabinofuranosylcytosine 5'-triphosphate accumulation in leukemia cells during high-dose 1-beta-D-arabinofuranosylcytosine therapy.

Twenty-seven patients with refractory leukemia were treated with 1-beta-D-arabinofuranosylcytosine (ara-C), 0.3 to 3.0 g/m2 as i.v. infusions over 1, 2, 4, or 24 h. The pharmacokinetics of ara-C in plasma and its 5'-triphosphate (ara-CTP) in leukemic cells from peripheral blood were studied after a single infusion of 3 g/m2 over 2 h in 13 patients. Accumulation of ara-CTP in leukemic cells remained linear until 1 to 2 h after the infusion. At the time when the rate of ara-CTP accumulation deviated from linearity, the plasma concentration of ara-C was 5- to 20-fold lower [8.1 +/- 4.4 (SD) microM] than the steady-state level during the infusion. Plasma ara-C and cellular ara-CTP pharmacokinetics were studied after two serial infusions in 14 additional patients. Varying the duration of infusion of an ara-C dose between 1, 2, and 4 h (corresponding to infusion rates of 3000, 1500, and 750 mg/m2/h) did not substantially change the rate of ara-CTP accumulation by leukemic cells. The peak ara-CTP concentration and the area under the concentration times time curve (AUC) of ara-CTP in leukemic cells increased with prolongation of the infusion. Although steady-state concentration of ara-C and AUC of ara-C in plasma were proportionally reduced by 1.0 or 0.5 g/m2 infusion over 2 h, ara-CTP accumulation rate and AUC in leukemic cells did not change compared with administration of 3 g/m2 over 2 h. However, when the infusion rate was further reduced to 0.4 or 0.3 g/m2 over 2 h, resulting in steady-state plasma ara-C concentrations of less than 7 microM, the accumulation rate of ara-CTP was substantially reduced as was the ara-CTP intracellular AUC. The cellular elimination rate of ara-CTP remained constant under all infusion conditions. These findings support the conclusion that high-dose ara-C therapy, as currently administered, results in plasma ara-C concentrations that saturate the accumulation of ara-CTP by circulating leukemic cells. We recommend that intermediate dose rates, 200 to 250 mg/m2/h, be evaluated in future studies as an alternative to the substantially higher ara-C dose rates currently in use.

Fludarabine triphosphate inhibits nucleotide excision repair of cisplatin-induced DNA adducts in vitro.

Fludarabine (9-beta-arabinofuranosyl-2-fluoroadenine-5'-monophosphate) is clinically active against chronic lymphocytic leukemia and low-grade lymphomas. We reported previously that fludarabine nucleoside synergistically enhanced cisplatin (CDDP)-induced cytotoxicity in vitro, and that the synergism was concomitant with inhibition of removal of cellular CDDP-induced DNA interstrand cross-links, which are presumably repaired by homologous recombinational repair. To extend our work, we investigated whether fludarabine inhibits nucleotide excision repair (NER) of CDDP-induced DNA intrastrand adducts. The effect of fludarabine on NER was determined using a cell-free system in which a plasmid containing the DNA adducts served as the substrate for repair enzymes in whole-cell extracts from repair-competent cells. To prevent the cell-bound high mobility group box-containing proteins from interfering with repair, cell extracts were depleted with high mobility group box proteins by immunoprecipitation prior to the assay. Repair synthesis, measured by the incorporation of [(32)P]dATP or [(32)P]dCTP, was inhibited by 50% at 26 or 43 microM fludarabine triphosphate, respectively; the effect was dose dependent and may have resulted from the termination of repair-patch elongation. These results were consistent with those from pulse-chase experiments demonstrating the conversion of nicked circular plasmid to the closed circular form by cell extracts filling the repair gaps. When proliferating cell nuclear antigen-depleted cell extracts were used and aphidicolin was added in the repair assay to arrest NER at the incision/excision stage, 100 microM fludarabine triphosphate inhibited about 55% of the conversion of nicked plasmids from the closed circular damaged plasmid substrate; the inhibition was dose dependent. We conclude that fludarabine triphosphate inhibited NER at the steps of incision and repair synthesis. These results suggest that fludarabine may serve as a potential repair modulator to improve the antitumor efficacies of combination regimens containing agents that induce NER.

Pharmacologically directed design of the dose rate and schedule of 2',2'-difluorodeoxycytidine (Gemcitabine) administration in leukemia.

The objective of this study was to determine the dose rate of 2',2'-difluorodeoxycytidine (dFdC) that maximizes the accumulation of the active 5'-triphosphate (dFdCTP) in circulating leukemia cells during therapy. The investigational approach was to evaluate the relationship between plasma dFdC and the accumulation of dFdCTP by circulating leukemia cells during infusion of different dFdC dose rates in the same individuals. Four patients with relapsed leukemia were treated weekly with two or three consecutive infusions of 800 mg/m2, the first administered over 1 h, the second over 2 h, and the third over 3 h. Two patients, one with acute myelogenous leukemia and one with acute lymphocytic leukemia, received all three infusions, but thrombocytopenia prohibited infusion of the third dose to two patients with chronic lymphocytic leukemia. The average steady-state plasma dFdC levels, achieved within 15 min after the infusion began, were 43.8 microM during infusion of 800 mg/m2/h, 9.4 microM during infusion of 400 mg/m2/h, and 5.6 microM at 267 mg/m2/h. The median area under the concentration times time curve of dFdCTP in leukemia cells during infusion was increased 2.3- and 5.1-fold for the 2- and 3-h infusions, respectively. In vitro incubations of leukemia cells from the four patients with 2.5-100 microM dFdC for 1 h showed that the maximum cellular accumulation of dFdCTP was produced by 15-20 microM dFdC. We conclude that a dose rate of greater than 400 mg/m2/h was required to achieve plasma dFdC levels that supported the maximum rate of dFdCTP accumulation in leukemia cells.

Analysis of P210bcr-abl tyrosine protein kinase activity in various subtypes of Philadelphia chromosome-positive cells from chronic myelogenous leukemia patients.

An altered c-abl gene product (P210bcr-abl) possessing associated tyrosine protein kinase activity was recently been reported in several blast chronic myelogenous leukemia (CML) cell lines. We have examined different morphological types of leukocytes directly obtained from patients at the blast crisis stage of CML for expression of P210bcr-abl tyrosine protein kinase activity. Phosphorylation of P210bcr-abl in an immune complex kinase assay using an anti-v-abl peptide serum was observed in blast cells from four Philadelphia chromosome (Ph1)-positive CML patients in blast crisis. P210bcr-abl protein kinase activity was detected regardless of whether the blast cells were of myeloid, lymphoid, or undifferentiated morphology. P210bcr-abl protein kinase activity was not detected in immune complexes either from leukocytes of four Ph1-negative CML patients in blast crisis, of five acute myelogenous leukemia patients, or in the promyelocytic cell line HL-60. Mature myeloid cells are associated with an inhibitory factor for not only P210bcr-abl protein kinase activity, but also protein kinases in general. Therefore, analyses of Ph1-positive benign phase CML myeloid cells, the majority of which are well differentiated, could not be successfully performed. The inhibition of P210bcr-abl protein kinase activity is not a specific property of mature cells from CML patients since granulocytes from a normal volunteer also demonstrated a similar effect. However, extracts of Ph1-positive cultured B-lymphocytes from a patient in benign phase demonstrated active P210bcr-abl protein indicating that the P210bcr-abl protein is expressed in an enzymatically active form in the earlier phases of CML. In addition to the previously reported P210 and P190 abl-related proteins, a novel Mr 53,000 protein was found to undergo phosphorylation at serine and tyrosine in immune complex kinase assays of two blast crisis CML cell lines (K562 and EM2) and in samples from blast crisis patients in which P210bcr-abl was detected. Peptide mapping by the Cleveland technique suggested that Mr 53,000 protein is unrelated to P210bcr-abl. Immune complex kinase assays of K562 cells with an anti-src serum (GD-11) yielded active c-src kinase and a Mr 50,000 phosphorylated protein, both of which were resistant to alkaline hydrolysis. Peptide mapping suggested that Mr 53,000 protein is related to Mr 50,000 protein which is precipitated with P210bcr-abl as an Mr 300,000 protein complex.

Characterization of the 13q14 tumor suppressor locus in CLL: identification of ALT1, an alternative splice variant of the LEU2 gene.

Chromosome 13q14 deletions constitute the most common genetic abnormality in chronic lymphocytic leukemia (CLL). To identify the putative tumor suppressor gene targeted by 13q14 genomic loss, we completely sequenced and characterized a segment of 790 kb at 13q14 spanning the minimal region of loss in CLL. Transcribed sequences in the region were identified through database homology searches and exon-prediction analysis. Two-hundred kb at the centromeric end of the sequence contain five CpG islands, three previously identified genes LEU5/RFP2, LEU2, and LEU1, seven of seven EST clusters composed of >10 ESTs, and a large number of predicted exons. Homology searches against the mouse EST database have allowed us to identify a highly conserved alternative first exon of the LEU2 gene, giving rise to a novel transcript, ALT1 (GenBank accession no. AF380424), which originates within a G+C region in the vicinity of the D13S272 marker. Two novel 3' exons of LEU2 were also identified and are present in both LEU2 and ALT1 transcripts. However, we have not identified any mutations in leukemia cases, or alterations in expression of mRNAs in the region, that might directly implicate these mRNAs in the pathology of CLL. The centromeric end of the sequence, where all reported genes are located, contains twice the expected amount of ALU repeats, whereas the telomeric end is LINE1 rich and contains four LINE1 elements longer than 4 kb, including two full-length LINE1 sequences. This feature of the sequence may favor the occurrence of chromosomal rearrangements and may confer instability to the region, resulting in deletions that may inactivate an as yet unidentified tumor suppressor.

ATM function and its relationship with ATM gene mutations in chronic lymphocytic leukemia with the recurrent deletion (11q22.3-23.2).

Approximately 10-20% of chronic lymphocytic leukemia (CLL) patients exhibit del(11q22-23) before treatment, this cohort increases to over 40% upon progression following chemoimmunotherapy. The coding sequence of the DNA damage response gene, ataxia-telangiectasia-mutated (ATM), is contained in this deletion. The residual ATM allele is frequently mutated, suggesting a relationship between gene function and clinical response. To investigate this possibility, we sought to develop and validate an assay for the function of ATM protein in these patients. SMC1 (structural maintenance of chromosomes 1) and KAP1 (KRAB-associated protein 1) were found to be unique substrates of ATM kinase by immunoblot detection following ionizing radiation. Using a pool of eight fluorescence in situ hybridization-negative CLL samples as a standard, the phosphorylation of SMC1 and KAP1 from 46 del (11q22-23) samples was analyzed using normal mixture model-based clustering. This identified 13 samples (28%) that were deficient in ATM function. Targeted sequencing of the ATM gene of these samples, with reference to genomic DNA, revealed 12 somatic mutations and 15 germline mutations in these samples. No strong correlation was observed between ATM mutation and function. Therefore, mutation status may not be taken as an indicator of ATM function. Rather, a direct assay of the kinase activity should be used in the development of therapies.

Outcomes for patients with chronic lymphocytic leukemia and acute leukemia or myelodysplastic syndrome.

Acute leukemia (AL) and myelodysplastic syndrome (MDS) are uncommon in chronic lymphocytic leukemia (CLL). We retrospectively identified 95 patients with CLL, also diagnosed with AL (n=38) or MDS (n=57), either concurrently (n=5) or subsequent (n=90) to CLL diagnosis and report their outcomes. Median number of CLL treatments prior to AL and MDS was 2 (0-9) and 1 (0-8), respectively; the most common regimen was purine analog combined with alkylating agent±CD20 monoclonal antibody. Twelve cases had no prior CLL treatment. Among 38 cases with AL, 33 had acute myelogenous leukemia (AML), 3 had acute lymphoid leukemia (ALL; 1 Philadelphia chromosome positive), 1 had biphenotypic and 1 had extramedullary (bladder) AML. Unfavorable AML karyotype was noted in 26, and intermediate risk in 7 patients. There was no association between survival from AL and number of prior CLL regimens or karyotype. Expression of CD7 on blasts was associated with shorter survival. Among MDS cases, all International Prognostic Scoring System (IPSS) were represented; karyotype was unfavorable in 36, intermediate in 6 and favorable in 12 patients; 10 experienced transformation to AML. Shorter survival from MDS correlated with higher risk IPSS, poor-risk karyotype and increased number of prior CLL treatments. Overall, outcomes for patients with CLL subsequently diagnosed with AL or MDS were very poor; AL/MDS occurred without prior CLL treatment. Effective therapies for these patients are desperately needed.