All-trans retinoic acid (ATRA) therapeutical effect in acute promyelocytic leukemia

ATPR induces acute promyelocytic leukemia cells differentiation and cycle arrest via the lncRNA CONCR/DDX11/PML-RARα signaling axis

Acute promyelocytic leukemia (APL) is a type of acute myeloid leukemia (AML) with a high mortality rate, and the production of PML-RARα fusion protein is the cause of its pathogenesis. Our group has synthesized a novel compound, 4-amino-2-trifluoromethyl-phenyl retinate (ATPR), by structural modification of All-trans retinoic acid (ATRA), which has strong cell differentiation-inducing effects and inhibits the expression of PML-RARα. In this study, acute promyelocytic leukemia NB4 cells before and after ATPR induction were analyzed by whole transcriptome microarray, and the expression of lncRNA CONCR was found to be significantly downregulated. The role of CONCR in ATPR-induced cell differentiation and cycle arrest was explored through overexpression and silencing of CONCR. And then the database was used to predict that CONCR may bind to DEAD/H-Box Helicase 11 (DDX11) protein to further explore the role of CONCR binding to DDX11. The results showed that ATPR could reduce the expression of CONCR, and overexpression of CONCR could reverse the ATPR-induced cell differentiation and cycle blocking effect, and conversely silencing of CONCR could promote this effect. RNA immunoprecipitation (RIP) experiments showed that CONCR could bind to DDX11, the protein expression levels of DDX11 and PML-RARα were elevated after overexpression of CONCR. These results suggest that ATPR can regulate the expression of DDX11 through CONCR to affect the expression of PML-RARα fusion protein, which in turn induces the differentiation and maturation of APL cells.

A Retinol Derivative Inhibits SARS-CoV-2 Infection by Interrupting Spike-Mediated Cellular Entry

Retinoids, a group of compounds including vitamin A and its active metabolite all- trans retinoic acid (ATRA), regulate serial physiological activity in multiple organ systems, such as cell growth, differentiation, and apoptosis. The ATRA analogues reported to date include more than 4,000 natural and synthetic molecules that are structurally and/or functionally related to ATRA.

Prioritizing targets for precision cancer medicine

The implementation of cancer genomic testing into the clinical setting has brought major opportunities. However, as our understanding of cancer initiation, maintenance and progression improves through detailed cancer genomic studies, the challenges associated with driver identification and target classification in the clinical setting become clearer. Here, we review recent insights into cancer genomic testing in the clinical setting, and suggest a target classification approach that considers the levels of evidence supporting the prioritization of tumour drivers for therapeutic targeting in light of complex cancer clonal and sub-clonal structures and clinical successes and failures in the field. We argue that such classification approaches, together with transparent reporting of both positive and negative clinical data and continued research to identify the sub-clonal dynamics of driver events during the disease course, will facilitate inter-trial comparisons, optimize patient informed consent and provide a critically balanced evaluation of genomic testing in clinical practice.

Promyelocytic sarcoma of the spine: a case report and review of the literature

Myeloid sarcoma (MS, previously named granulocytic sarcoma or chloroma) is a rare extramedullary tumour of immature myeloid cells. It can be present before, concurrently with, or after the diagnosis of acute myeloid leukemia. MS is extremely uncommon in acute promyelocytic leukemia (APL). In the case described here, MS was the sole site of APL relapse and the cause of spinal cord compression. The patient presented with neurologic symptoms due to a paravertebral mass of MS after 7 years of complete remission. He was treated with excision of the mass followed by local radiotherapy. Systemic treatment was also given with combined arsenic trioxide and all-trans retinoic acid and the patient was able to achieve a second prolonged clinical and molecular remission.

FAB M4 and high CD14 surface expression is associated with high cellular resistance to Ara-C and daunorubicin: implications for clinical outcome in acute myeloid leukaemia

In 145 adult patients diagnosed with non-M3 acute myeloid leukaemia (AML) the relevance of FAB-subtype and immunophenotype to in vitro cellular drug resistance towards the anthracyclines aclarubicin (Acla) and daunorubicin (Dau), and the nucleoside analogue cytarabine (Ara-C), as well as other antileukaemic drugs, was investigated using a 4-d MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide) assay. We demonstrate that high CD14 expression is highly significantly associated with high cellular Ara-C and Dau resistance in univariate as well as multivariate analyses. FAB subtypes with highest and lowest cellular Ara-C resistance were M4 and M5, respectively (P < 0.01, one-way anova), whereas FAB subtypes with highest and lowest cellular Dau resistance were M4 and M1, respectively (P < 0.01, one-way anova). By contrast, no significant differences in cellular drug resistance towards Acla could be demonstrated among FAB subtypes. Furthermore, in two cohorts of AML patients treated by two different regimens for remission induction over a period of 15 yr (1985-94, n = 159 and 1995-99, n = 76, respectively) we demonstrate in univariate analyses a significance of CD14 expression with respect to clinical outcome. With the exception of significance to probability of obtaining complete remission in the first cohort (P = 0.03, logistic regression), this significance was, however, lost in multivariate analyses. It was demonstrated that FAB-M4 patients were older than M5 patients and that high CD14 expression was associated with the presence of secondary AML and older age. We conclude that although cases with high blast cell CD14 expression (and FAB-M4 cases) were more resistant to Ara-C as well as Dau in vitro, the clinical and biological significance of this may be debatable because of interactions with major prognostic factors in AML.

Common themes in the pathogenesis of acute myeloid leukemia

The pathogenesis of acute myeloid leukemia is associated with the appearance of oncogenic fusion proteins generated as a consequence of specific chromosome translocations. Of the two components of each fusion protein, one is generally a transcription factor, whereas the other partner is more variable in function, but often involved in the control of cell survival and apoptosis. As a consequence, AML-associated fusion proteins function as aberrant transcriptional regulators that interfere with the process of myeloid differentiation, determine a stage-specific arrest of maturation and enhance cell survival in a cell-type specific manner. The abnormal regulation of transcriptional networks occurs through common mechanisms that include recruitment of aberrant co-repressor complexes, alterations in chromatin remodeling, and disruption of specific subnuclear compartments. The identification and analysis of common and specific target genes regulated by AML fusion proteins will be of fundamental importance for the full understanding of acute myeloid leukemogenesis and for the implementation of disease-specific drug design.

Correlation of differentiation-inducing activity of retinoids on human leukemia cell lines HL-60 and NB4

Retinoids, including all-trans-retinoic acid, its isomers, and fifty synthetic retinoids (retinobenzoic acids), were tested for differentiation-inducing activity on human leukemia cell lines HL-60 and NB4. A good linear correlation, with an r value of 0.91, between the ED50 values for the differentiation-inducing activity towards HL-60 cells and that towards NB4 cells was found.

Retinoids inhibit mammalian glutathione transferases

Affinity-purified cytosolic glutathione transferases from adult female rat liver, adult human liver and human term placenta were used. Of the 8 retinoids tested, all-trans retinoic acid was found to be the most potent inhibitor of placental glutathione transferase. The inhibition was non-competitive and exhibited Ki values of 20 and 41 microM for all-trans retinoic acid in the presence of varying concentrations of 1-chloro-2,4-dinitrobenzene and glutathione, respectively. Micromolar all-trans retinoic acid also caused significant (30-90%) inhibition of rat and human liver glutathione transferases. Taken together, the data suggest that inhibition of glutathione transferase(s) may represent yet another mechanism of retinoid action.

The thymus extract Thymex-L potentiates the retinoic acid-induced differentiation of the human myeloid leukemia cell line HL-60

The human promyelocytic cell line HL-60 can be differentiated with retinoic acid (RA) along the granulocytic pathway. Numerous studies have identified many synergistic combinations of RA with cytostatics, cytokines and other inducers. A combination of RA with the crude thymus extract Thymex-L increased differentiation of HL-60 cells as confirmed by two functional assays and morphology, whereas the extract itself did not show any effect. The functional markers phagocytosis-associated chemiluminescence and nitroblue tetrazolium reduction were more enhanced (up to 4-fold with 1000 micrograms/ml Thymex-L) than morphology. The effect was found over a wide RA concentration range (10(-11) - 10(-6) M) and was dependent on extract concentration. The half-maximal induction of both functional markers was reached at 400 micrograms/ml. To achieve the same effect with the combination in comparison with RA alone, an RA dose reduction of about 100-fold was estimated. The effect was also seen when the cells were pretreated with the thymus extract for two days. The enhancement of RA action by Thymex-L was not correlated with an increase of extracellular or intracellular RA concentration. The active compound in Thymex-L is heat stable and bigger than 5 kDa as confirmed by gelfiltration. The defined thymus peptides thymosin alpha 1, prothymosin alpha 1 and thymopentin were unable to synergistically enhance HL-60 differentiation. These data suggest that the treatment with a thymus extract can increase the sensitivity of HL-60 cells for RA. This may have clinical implications.

Saffron chemoprevention in biology and medicine: a review

A growing body of evidence indicate that carotenoids possess anticarcinogenic, anti-mutagenic and immunomodulating effects. Saffron obtained from the dried stigmas of Crocus sativus L., is an important spice, rich in carotenoids, consumed commonly in different parts of the world. Our laboratory first reported the anticancer activity of saffron extract (dimethyl-crocetin) against a wide spectrum of murine tumors and human leukemia cell lines. The present report reviews the role of saffron in serving as a chemopreventive agent in modifying cancer risk. Dose-dependent cytotoxic effect to carcinoma, sarcoma and leukemia cells in vitro were noted. Saffron delayed ascites tumor growth and increased the life span of the treated mice compared to untreated controls by 45-120%. In addition, it delayed the onset of papilloma growth, decreased incidence of squamous cell carcinoma and soft tissue sarcoma in treated mice. Understanding the mechanisms of action of saffron have been solitarily based on their carotenoid-like action. Our results indicated significant inhibition in the synthesis of nucleic acids but not protein synthesis. It appears now that saffron (dimethyl-crocetin) disrupts DNA-protein interactions e.g. topoisomerases II, important for cellular DNA synthesis.

Establishment of a retrodifferentiated cell line from a single differentiated rat myelomonocytic leukemia cell: possible roles of retrodifferentiation in relapses of leukemia after differentiation-inducing therapy

In order to demonstrate possible roles of retrodifferentiation in relapses after differentiation therapies, we have established a retrodifferentiated cell line (RD-1) from a single rat myelomonocytic leukemia cell which differentiated into a macrophage-like cell by treatment with lipopolysaccharide (LPS). The established RD-1 cells showed microscopic features slightly maturer than their parent cells. The RD-1 cells had the ability to differentiate into macrophage-like cells by treatment with fewer doses of LPS than those for parent cells. All rats inoculated with the parent cells (more than 10(2)/rat) died within 50 days. Rats inoculated with 10(4) RD-1 cells survived for more than 120 days, whereas two out of four rats inoculated with 10(5) cells and all the rats inoculated with 5 x 10(5) cells died of leukemia. These results suggest that RD-1 cells are retrodifferentiated cells from a single rat myelomonocytic leukemia cell which differentiated into a macrophage-like cell; they have similar phenotypes and lower tumorigenicity than the parent cells and they also suggest that the appearance of retrodifferentiated leukemia cells may be responsible for relapse after differentiation therapy for leukemia in some cases.

Retinoid receptors and acute promyelocytic leukaemia

While a great deal has been learned about APL over the last few years, many important questions remain unanswered. It has become clear that the PML/RAR-alpha fusion protein is expressed in most cases of APL, and this protein presumably contributes to leukaemia initiation and/or progression. PML/RAR-alpha appears to specifically block the further differentiation of myeloid progenitor cells, although the mechanism of its action is not known. It may inhibit the transcription of RAR- or PML-regulated genes, in which case expression must be restored in the presence of therapeutic RA concentrations. However, the possibility remains that PML/RAR-alpha may have a novel function. In order to elucidate the molecular pathogenesis of APL, several important questions remain to be answered. These include whether PML is a transcription factor; the identification of its target genes and response elements, and the role of PML/RAR-alpha and RA in their regulation. Also whether the expression of PML/RAR-alpha in bone marrow cells (either by itself or in combination with other oncogenes) alters their tumourigenicity or differentiation potential. It is also important to determine the function(s) of PLZF and PLZF/RAR-alpha, and determine whether other APL patients with mutations involving PML or RAR-alpha (but not both) respond to therapy with all-trans-RA. Finally, it is important both for the understanding of the molecular biology of APL and its therapy, to determine the effects of other regulatory factors involved in the control of myeloid cell differentiation such as granulocyte colony stimulation factor (G-CSF) and granulocyte macrophage colony stimulating factor (GM-CSF) on APL cells in vitro and in vivo, both at presentation and in the RA-resistant patients in relapse.