Dichotomy of all-trans retinoic acid inducing signals for adult T-cell leukemia

All-Trans Retinoic Acid Exhibits Antiviral Effect against SARS-CoV-2 by Inhibiting 3CLpro Activity

The pandemic of COVID-19 caused by SARS-CoV-2 continues to spread despite the global efforts taken to control it. The 3C-like protease (3CLpro), the major protease of SARS-CoV-2, is one of the most interesting targets for antiviral drug development because it is highly conserved among SARS-CoVs and plays an important role in viral replication. Herein, we developed high throughput screening for SARS-CoV-2 3CLpro inhibitor based on AlphaScreen. We screened 91 natural product compounds and found that all-trans retinoic acid (ATRA), an FDA-approved drug, inhibited 3CLpro activity. The 3CLpro inhibitory effect of ATRA was confirmed in vitro by both immunoblotting and AlphaScreen with a 50% inhibition concentration (IC50) of 24.7 ± 1.65 µM. ATRA inhibited the replication of SARS-CoV-2 in VeroE6/TMPRSS2 and Calu-3 cells, with IC50 = 2.69 ± 0.09 µM in the former and 0.82 ± 0.01 µM in the latter. Further, we showed the anti-SARS-CoV-2 effect of ATRA on the currently circulating variants of concern (VOC); alpha, beta, gamma, and delta. These results suggest that ATRA may be considered as a potential therapeutic agent against SARS-CoV-2.

Apoptosis as a mechanism for the treatment of adult T cell leukemia: promising drugs from benchside to bedside

Human T cell lymphotropic virus-1 (HTLV-1) is the causative agent of adult T cell leukemia (ATL), an aggressive malignancy of mature activated T cells. Although many therapeutic strategies are available, none are effective and most patients experience recurrence of the disease. Over the past decade, many drugs have been discovered that showed promising therapeutic potential against ATL but which remain in the preclinical testing phase. Mechanistically, these drugs either induce apoptosis or regulate cellular proliferation in ATL cells. Here, we provide a summary of these promising drugs that target ATL, with a focus on their mechanism of anticancer activity, to offer insights into the use of multiple drugs with different targets for enhancing ATL eradication.

Nanostructured lipid carriers loaded with tributyrin as an alternative to improve anticancer activity of all-trans retinoic acid

OBJECTIVES

All-trans retinoic acid (ATRA) is one of the most successful examples of differentiation agents and histone deacetylase inhibitors, such as tributyrin (TB), are known for their antitumor activity and potentiating action of drugs, such as ATRA. Nanostructured lipid carriers (NLC) represent a promising alternative to the encapsulation of lipophilic drugs such as ATRA. This study aims to develop, characterize and evaluate the cytotoxicity of ATRA-TB-loaded NLC for cancer treatment.

METHODS

The influence of in situ formation of an ion pairing between ATRA and a lipophilic amine (benethamine) on the characteristics of NLC (size, zeta potential, encapsulation efficiency) was evaluated. TB, a butyric acid donor, was used as a component of the lipid matrix. In vitro activity on cell viability and distribution of cell cycle phases were evaluated for MCF-7, MDA-MB-231, HL-60 and Jurkat cell lines.

RESULTS

The presence of the amine significantly increased the encapsulation efficiency of ATRA in NLC. Inhibition of cell viability by TB-ATRA-loaded NLC was more pronounced than the free drug. Analysis of the distribution of cell cycle phases also showed increased activity for TB-ATRA-loaded NLC, with the clear effect of cell cycle arrest in G0/G1 phase transition. The presence of TB played an important role in the activity of the formulation.

CONCLUSION

Taken together, these findings suggest that TB-ATRA-loaded NLC represents a promising alternative to intravenous administration of ATRA in cancer treatment.

All-trans retinoic acid attacks reverse transcriptase resulting in inhibition of HIV-l replication

We previously reported that all-trans retinoic acid (ATRA) inhibited growth in HTLV-1-positive T-cell lines and fresh cells from patients with adult T-cell leukemia. Interestingly, ATRA significantly inhibited reverse transcriptase (RT) activity similar to azidothimidine (AZT) in HTLV-1-positive T-cell lines. To clarify whether ATRA has an inhibitory effect on the replication of HIV, we examined HIV proviral DNA in a HIV-1-positive cell line (8E5) using real time PCR. ATRA as well as AZT reduced the proviral DNA load of 8E5 in a dose-dependent manner. These results suggest that there is a common element of ATRA signaling in both HTLV-1 and HIV. Furthermore, we examined the effects of ATRA on viral replication in primary lymphocytes of three individuals infected with HIV. ATRA reduced viral replication significantly similar to AZT. These findings suggested that ATRA acts as a RT inhibitor, reducing the HIV-1 proviral DNA load. Finally, we conclude that ATRA may be a potential therapeutic agent for HIV infection.

Function of retinoid acid receptor alpha and p21 in all-trans-retinoic acid-induced acute T-lymphoblastic leukemia apoptosis

All-trans-retinoic acid (ATRA) is a morphogenetic signalling molecule derived from vitamin A and is used clinically to target acute promyelocytic leukemia by inducing differentiation of immature blood cells. Retinoid signals are mediated by retinoic acid (RA) receptors (RARs) and retinoid X receptors (RXRs). Retinoic acid receptors consist of RARalpha, RARbeta and RARgamma isotypes. Among these components, RARalpha is preferentially bound to ATRA, which is used to treat acute T-lymphoblastic leukemia, yet the conditions and mechanisms remain unknown. In this study, we have demonstrated that, in human acute T-lymphoblastic leukemia Molt3 cells, inhibition of RA-induced proliferation results from massive cell death characterised by apoptosis. The effect of ATRA:RARalpha binding on apoptosis in Molt3 cells has been investigated. Consequently, it has been shown that, in RA-treated Molt3 cells, upregulation of p21 due to RA accompanies caspase 3/PARP activation which precedes the occurrence of apoptosis.

Complete remission of a relapsing adult T cell leukaemia following treatment of a secondary acute promyelocytic leukaemia: towards a reappraisal of arsenic trioxide and all-transretinoic acid?

Despite improvements in therapeutic options, human T cell lymphotropic virus type 1 (HTLV-1)-related adult T cell leukaemia/lymphoma (ATLL) has a dismal prognosis. The present report concerns the case of a multirelapsing ATLL that reached a complete remission following the treatment of a secondary acute promyelocytic leukaemia with cytarabine, anthracyclin, all-transretinoic acid and arsenic trioxide. This unexpected result with a multitreated/chemorefractory disease led us to reconsider the potential therapeutic benefits of arsenic trioxide, which has demonstrated efficacy against ATLL cells.

Clinical efficacy of all-trans retinoic acid for treating adult T cell leukemia

PURPOSE

We previously reported that all-trans retinoic acid (ATRA) inhibited growth in human T-cell leukemia virus type I (HTLV-I)-positive T-cell lines and in fresh cells from patients with adult T cell leukemia (ATL). Here, we confirmed the clinical effects of ATRA in 20 patients with ATL.

MATERIALS AND METHODS

The 20 patients (n = 20) with a median age of 56 (range 35-73) years who were diagnosed with ATL received ATRA orally.

RESULTS

The efficacy of treatment was as follows: no complete response (CR), a partial response (PR) in 40% of the patients, no change (NC) in 45% of the patients, and a progressive disease (PD) in 15% of the patients. In seven acute-type ATL patients, a PR was achieved in two (28.5%), NC was observed in two (28.5%), and a PD was observed in three (42.8%). In three lymphoma-type ATL patients, a PR (100%) was achieved. Among four chronic-type ATL patients, a PR was achieved in one (25%) and NC was observed in the remaining three (75%). In six smoldering-type ATL patients, a PR was achieved in two (33.3%) and NC was observed in four (66.6%). The major side effects were headache (n = 5), transient liver dysfunction (n = 2), hyperlipidemia (n = 2), and anorexia (n = 1).

CONCLUSION

These results indicated that ATRA might be a useful agent for the safe treatment of ATL.

Designed ATRA analogue active against ATRA-resistant acute promyelocytic leukemia cells having a single nucleotide substitution in their retinoic acid receptor

All-trans retinoic acid (ATRA) induces the differentiation of acute promyelocytic leukemia (APL) cells into neutrophils. UF-1 cells were established from an ATRA-resistant APL patient, and were previously shown to possess a single amino acid (or nucleotide) substitution, Arg276Trp, in their ATRA receptor. In the present research, we designed several ATRA derivatives having a hydrophobic alkyl ketone moiety instead of the negatively charged carboxylic acid moiety. Among them the ethyl ketone derivative, Et-ketone ATRA, was shown to induce the differentiation of UF-1 cells when assessed in terms of intracellular ROS production. It also induced the formation of PML NBs and expression of CD11b antigen marker and p21, transcriptional targets of RARalpha. Et-ketone ATRA did not induce these phenotypic changes in wild-type APL NB4 cells. Furthermore, we found that Et-ketone ATRA induced apoptosis selectively in UF-1 cells, i.e., not in other leukemic cells. The induction of apoptosis was shown to be partly due to the up-regulation of Bax protein. Thus, Et-ketone ATRA selectively induced differentiation and apoptosis in ATRA-resistant APL UF-1 cells, and is likely to be useful for the clinical treatment of the Arg276Trp-type of ATRA-resistant APL.