T cell receptor excision circles are potential predictors of survival in adult allogeneic hematopoietic stem cell transplantation recipients with acute myeloid leukemia

Background

Lymphocyte neogenesis from primary lymphoid organs is essential for a successful reconstitution of immunity after allogeneic hematopoietic stem cell transplantation (HSCT). This single-center retrospective study aimed to evaluate T cell receptor excision circles (TREC) and kappa-deleting recombination excision circles (KREC) as surrogate markers for T and B cell recovery, as predictors for transplantation-related outcomes in adult acute myeloid leukemia (AML) patients.

Methods

Ninety adult patients diagnosed with AML and treated with HSCT between 2010 and 2015 were included in the study. TREC and KREC levels were measured by quantitative PCR at 1, 3, 6, and 12 months after transplantation.

Results

Overall, excision circle levels increased between 3 and 6 months post-HSCT for TREC (p = 0.005) and 1 and 3 months for KREC (p = 0.0007). In a landmark survival analysis at 12 months post-HSCT, TREC levels were associated with superior overall survival (HR: 0.52, 95% CI: 0.34 - 0.81, p = 0.004). The incidence of viral infections within the first 100 days after transplantation was associated with lower TREC levels at 6 months (p = 0.0002). CMV reactivation was likewise associated with lower TREC levels at 6 months (p = 0.02) post-HSCT. KREC levels were not associated with clinical outcomes in statistical analyzes.

Conclusions

Results from the present study indicate that TREC measurement could be considered as part of the post-HSCT monitoring to identify AML patients with inferior survival after transplantation. Further prospective studies are warranted to validate these findings.

APR-246 exhibits anti-leukemic activity and synergism with conventional chemotherapeutic drugs in acute myeloid leukemia cells

BACKGROUND

APR-246 belongs to a new generation of the compounds that restore normal p53 function in cells with mutated or wild type p53. The purpose of this study was to examine the effects of APR-246 alone and in combination with other drugs in acute myeloid leukemia (AML) cells.

METHODS

Primary leukemic cells from patients with AML and AML cell lines were studied with respect to cytotoxic and apoptotic effects and mechanism of action of APR-246, alone and in combination with Ara-C, daunorubicin and fludarabine.

RESULTS

APR-246 showed dose-dependent cytotoxic and apoptotic effects in AML cell lines as well as in primary AML patient cells. Cells from patients with TP53 mutation and complex karyotype were more resistant to conventional drugs while these factors did not significantly affect the sensitivity to APR-246. APR-246 increased active caspase-3, upregulated p53 protein levels, and increased the bax/bcl-2 ratio independently of TP53 mutational status in patient cells sensitive to APR-246. AML cells with high p14(ARF) expression were significantly more sensitive to APR-246. APR-246 induced significant synergistic effects in combination with conventional chemotherapeutic agents. Pre-incubation with APR-246 induced more synergistic effects compared to other schedules. In patient cells, pronounced synergism was found when combining APR-246 with danuorubicin.

CONCLUSION

We conclude that APR-246 is effective in AML cells irrespectively of TP53 mutational status and that it has promising properties for combination studies in AML.

Selenite is a potent cytotoxic agent for human primary AML cells

Selenite is a potent inhibitor of malignant cell growth. Although the cytotoxic effects have been extensively investigated in vitro, there are only a limited number of studies using primary tumor cells with concomitant comparison to conventional drugs. An ex vivo model with primary cells from 39 consecutive patients with acute myeloid leukemia (AML) were exposed to a panel of conventional cytotoxic drugs, and the effects on viability were compared to those of clinically achievable concentrations of selenite. Selenite at 5 microM caused the lowest mean survival of primary tumor cells in the panel of all tested drugs (28.95% CI 18.60-39.30%). The cells showed a significant (p<0.05) correlation in the resistance to all tested conventional AML drugs whereas selenite did not, indicating sensitivity to selenite also in multi drug resistant cells. Exposure to selenite also resulted in an increased mRNA expression of the antioxidant proteins TrxR1 and Grx, while staining for TrxR1 showed decreased protein levels. The results strongly suggest a great potential for selenite in the treatment of multi drug resistant AML.

Effects of the antioxidant Pycnogenol on cellular redox systems in U1285 human lung carcinoma cells

Pycnogenol, which is extracted from the bark of French maritime pine, has been shown to have antioxidant and free radical scavenging activities. Thioredoxin reductase (TrxR), glutathione peroxidase (GPx) and glutathione reductase (GR) are three central redox enzymes that are active in endogenous defence against oxidative stress in the cell. Treatment of cells with Pycnogenol decreased the activity of both TrxR and GPx in cells by more than 50%, but GR was not affected. As previously reported, both enzymes were induced after treatment with hydrogen peroxide and selenite. The presence of Pycnogenol efficiently decreased selenite-mediated reactive oxygen species (ROS) production. Addition of Pycnogenol after selenite treatment reduced the mRNA expression and activity of TrxR to basal levels. In contrast, the GPx activity was completely unaffected. The discrepancy between TrxR and GPx regulation may indicate that transcription of TrxR is induced primarily by oxidative stress. As TrxR is induced in various pathological conditions, including tumours and inflammatory conditions, decreased activity mediated by a non-toxic agent such as Pycnogenol may be of great value.

Higher plasma but not intracellular concentrations after infusion with liposomal daunorubicin compared with conventional daunorubicin in adult acute myeloid leukemia

To investigate the plasma and intracellular pharmacokinetics of liposomal daunorubicin (DaunoXome) in comparison with conventional daunorubicin, 14 patients aged 28 to 60 years with newly diagnosed acute myeloid leukemia were treated for 1 day with DaunoXome (50 mg/m) and for 2 days with daunorubicin (50 mg/m) with concomitant Ara-C (7 days, 200 mg/m, continuous IV). Eleven of the 14 patients entered complete remission; 9 are still alive. Pharmacokinetic profiles were obtained by blood sampling at appropriate intervals on days 1 to 4. Daunorubicin and daunorubicinol concentrations in plasma and in peripheral leukemic blast cells were measured by high-performance liquid chromatography. Following liposomal daunorubicin administration, the peak values and plasma area under the curve (AUC) were more than 100 times higher than after administration of conventional daunorubicin (AUC, 176 vs. 0.98 micromol/L x hour), but the intracellular AUCs were comparable (759 vs. 715 micromol/L x hour). Intracellular concentrations after DaunoXome peaked later and half as high as after daunorubicin. After DaunoXome versus daunorubicin, plasma clearance was 0.001 versus 0.4 micromol/h, respectively. The volume of distribution was 5.5 L for DaunoXome, versus 3640 L for daunorubicin, indicating low tissue affinity for the liposomal formulation. The authors conclude that liposomal daunorubicin, DaunoXome, yields 2-log higher plasma concentrations but similar intracellular concentrations of daunorubicin and its metabolite daunorubicinol than does free daunorubicin.

Mammalian thioredoxin reductase alters cytolytic activity of an antibacterial peptide

Granulysin is a disulfide rich 9 kDa human tumoricidal protein produced by cytolytic cells. Here we show that thioredoxin reductase (TrxR) reduced a 23-residue peptide from granulysin (GranF2), and this markedly enhanced the killing of small cell lung cancer cells (SCLC) by GranF2. Cells treated with reduced GranF2 showed rapid ATP deletion within 90 min and strong annexin V staining after 4 h incubation. SCLC with elevated TrxR levels was more sensitive to oxidized GranF2 than normal cells. The levels of TrxR are enhanced in many cancer cells, including SCLC, and it is possible that cytolytic activity of cytolytic cells on SCLC may in part be mediated by granulysin and modulated by TrxR.

Selenite-induced apoptosis in doxorubicin-resistant cells and effects on the thioredoxin system

Selenium treatment of the doxorubicin-resistant cell line, U-1285dox, derived from human small cell carcinoma of the lung, resulted in massive apoptosis. This effect appeared maximal at 2 days after addition of selenite. The apoptosis was caspase-3 independent as revealed by Western blot analysis, activity measurement and by using caspase inhibitors. Induction of apoptosis was significantly more pronounced and occurred after addition of lower concentrations of selenite in the doxorubicin-resistant cells compared to the parental doxorubicin-sensitive cells. High levels of selenite caused necrosis in the doxorubicin-sensitive cells. Analysis of enzymatic activity (insulin reduction) of thioredoxin reductase (TrxR) and TrxR protein concentration, measured by ELISA, revealed increasing activity and protein levels after treatment with increasing concentrations of selenium. Maximum relative increase was induced up to 1 microM in both sublines and at this selenium level the concentrations of TrxR measured as insulin reducing activity or ELISA immunoreactivity were nearly identical. Increasing concentrations of selenite up to 10 microM resulted in increased activity and concentration of TrxR in the sensitive subline but decreasing levels in the resistant subline. The level of truncated Trx (tTrx) was higher in the resistant U-1285dox cells but the level did not change with increasing selenite concentrations. Our results demonstrate pronounced selective selenium-mediated apoptosis in therapy-resistant cells and suggest that redox regulation through the thioredoxin system is an important target for cancer therapy.

Doxorubicin-resistant, MRP1-expressing U-1285 cells are sensitive to idarubicin

A doxorubicin-resistant subline (U-1285dox(900)) was derived from the human small cell lung carcinoma cell line U-1285. U-1285dox(900) was exposed to a wide range of anticancer agents to determine its resistance profile. In contrast to U-1285 cells, the resistant subline U-1285dox(900) expressed elevated MRP1 mRNA detected by reversed transcriptase-polymerase chain reaction (RT-PCR) and MRP1 protein analyzed with Western blot. Neither MDR1 mRNA nor P-glycoprotein could be detected in the parental cell line or resistant subline. U-1285dox(900) exhibited high resistance to doxorubicin, epirubicin, daunorubicin, and vincristine, an intermediate resistance to mitoxantrone, and a low resistance to etoposide. A collateral sensitivity to cytosine arabinoside, chlorodeoxyadenosine, and melphalan was observed. The resistance could be reversed by buthionine-sulphoximine and verapamil for all tested drugs. Compared with daunorubicin, resistance to idarubicin was very low, 14-fold and 2.6-fold, respectively. This was associated with a higher accumulation due to a slower transport of idarubicin out of U-1285dox(900) cells.