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- Lehmann, Sören
(författare)
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In vitro studies of retinoids and arsenic in non-M3 acute myeloid leukemia
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Despite advances in the treatment of patients with acute myeloid leukemia (AML), the majority of the patients will die from their disease. The current intensive therapy for AML is also complicated my substantial morbidity and mortality and, as a result, many patients cannot be given the most effective therapy. Therefore, the need for more effective as well as less toxic treatment approaches for AML is urgent. Retinoids and arsenic has recently shown impressive results in the treatment of acute promyelocytic leukemia (APL) and both drugs exhibit less toxic effects than the commonly used chemotherapeutic drugs. In these studies we have investigated the effects of retinoids and arsenic in cells from patients with non-APL (or non-M3) AML. Furthermore, we have investigated what mechanisms that could be of importance for the sensitivity to these drugs. The results showed that there is a pronounced heterogeneity in the sensitivity to the retinoids all-trans-retinoic acid (ATRA) and 9-cis-RA but cells from the majority of the patients were sensitive and some cases exhibited a pronounced sensitivity to retinoids. There was no cross-resistance between the retinoids and daunorubicin (DNR) and cells that were more resistant to DNR tended to be more retinoidsensitive. Also, CD34-positive AML cells were more sensitive than the CD34-negative. In order to find markers for retinoid sensitivity we correlated the expression of retinoid receptors (RARs and RXR alpha) and retinoid bindings proteins (CRBPI and CRABPs) to the sensitivity to ATRA in the patient samples. No correlation between the sensitivity to the retinoids and the basal mRNA expression of any of these proteins was found. However, upregulation of RAR beta and CRABPII after ATRA exposure did significantly correlate to retinoid sensitivity. For arsenic, a significant dose dependent sensitivity was found in all the patient samples even at concentrations below those that are seen in plasma during APL treatment. The sensitivity to arsenic was then compared to that of common AML drugs such as anthracyclines, etoposide, AMSA and Ara-C. There was a significant correlation in the sensitivity between the different anthracyclines as well as between the anthracyclines and etoposide and AMSA. However, all correlation coefficients were negative for the comparisons between arsenic and the other drugs and most so between arsenic and idarubicin. We then investigated the sensitivity to arsenic in P-gp-expressing cell lines showing that P-gp expression does not affect the sensitivity to arsenic. We also investigated the sensitivity in cell lines with either increased expression of MRP 1, downregulated topoisomerase II or in cells that were FAS-resistant. None of these resistant cell lines were shown to exhibit any decrease in sensitivity to arsenic compared to its non-resistant cell line. The only cell line that showed a decreased arsenic sensitivity was the lung cancer cell line GLC4/ADR. In addition to the overexpression of the lung resistance protein (LRP), these cells exhibited higher concentrations of GSH than the wild type GLG4. The multidrug resistant reverser and pyridine analogue PAK-104P exerted a powerful sensitizing effect on the cells together with arsenic, both in resistant and nonresistant cells. This sensitizing effect was accompanied by a slight decrease in GSH but this effect was moderate compared to the strong effect on cell toxicity. Therefore, we suggest that the sensitizing effect of PAK-104P should be further studied as well as its potential as a sensitizer to arsenic in vivo.
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| 2. |
- Lehmann, Sören, et al.
(författare)
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Retinoid receptor expression and its correlation to retinoid sensitivity in non-M3 acute myeloid leukemia blast cells
- 2001
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Ingår i: Clinical Cancer Research. - 1078-0432 .- 1557-3265. ; 7:2, s. 367-372
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Tidskriftsartikel (refereegranskat)abstract
- All-trans-retinoic acid (ATRA) has significantly improved the treatment results in acute promyelocytic leukemia (M3). In non-M3 acute myeloid leukemia (AML), the effects are less clear, and there is a pronounced heterogeneity in the sensitivity to the growth-inhibitory effects of retinoids in leukemic cells from different non-M3 AML patients. Retinoids exert their effects through a number of nuclear receptors [retinoic acid receptors (RARs) and retinoid X receptors (RXRs)]. In this study, we determined the expression of RAR alpha, RAR beta, RAR gamma, and RXR alpha by real-time PCR in four cell lines and in blast cells from patients with non-M3 AML before and after ATRA incubation. All four receptors were expressed in cells from all 18 tested patient samples and in four myeloid cell lines. In the majority of the patient samples as well as in the cell lines, there was a pattern of high expression of RAR alpha and RXR alpha and low expression of RAR beta and RAR gamma. There was no correlation between the basal expression of any of the retinoid receptors and sensitivity to ATRA. A 24-h exposure to ATRA increased the expression of RAR alpha, RAR beta, RAR gamma, and RXR alpha in 46%, 77%, 30%, and 38% of the samples, respectively. The mean increase in receptor expression was most pronounced for RAR beta and RXR alpha. There was a significant correlation between an increase in RAR beta expression in response to ATRA and sensitivity to ATRA (P < 0.014). No such correlations were found for RAR alpha, RAR gamma, and RXR alpha. The expression of the monocytoid marker CD14 was significantly correlated with increased expression of RAR alpha (P = 0.03). We conclude that RAR alpha, RAR beta, RAR gamma, and RXR alpha are expressed in non-M3 AML blast cells and that ATRA-induced expression of RAR beta may be a marker for retinoid sensitivity.
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| 3. |
- Lehmann, Sören, et al.
(författare)
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The expression of cellular retinoid binding proteins in non-APL leukemic cells and its association with retinoid sensitivity
- 2002
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Ingår i: Leukemia and Lymphoma. - : Informa UK Limited. - 1042-8194 .- 1029-2403. ; 43:4, s. 851-8
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Retinoic acid (RA) has important effects on cell differentiation and cell growth and on normal embryonic development. Intracellular retinoid signaling induced by endogenous or exogenous RA is regulated by retinoid binding proteins such as CRBPI, CRABPI and CRABPII and there are data suggesting that the expression of these proteins can influence the sensitivity to the growth inhibitory effects of ATRA. In this study, we investigated the basal and ATRA-induced expression of CRBPI and CRABPI and II in leukemic cell lines and in cells from patients with acute myeloid leukemia (AML). CRBPI as well as CRABPI and II were expressed in all tested cell lines and in leukemic cells from all 18 AML-patients. CRABPII mRNA expression was more abundant than CRBPI and CRABPI in both the cell lines and the patient cells but the levels compared the house keeping gene was lower in the patient cells. In all cell lines and in 69% of the patient samples, ATRA did upregulate CRABPII whereas CRBPI exhibited a varying response and CRABPI was more commonly downregulated. The sensitivity to the growth inhibitory effects of ATRA did not correlate with the basal expression of any of these proteins. However, ATRA-induced upregulation of CRABPII did significantly correlate with the ATRA sensitivity (p < 0.005) as well as with ATRA-induced upregulation of the retinoid receptor RARbeta (p < 0.05). We conclude that the retinoid binding proteins CRBPI and CRABPI and II are expressed in myeloid leukemic cells of non-M3 type but that the level of expression does not affect ATRA sensitivity.
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