Evi1 Counteracts Anti-Leukemic and Stem Cell Inhibitory Effects of All-Trans Retinoic Acid on Flt3-ITD/Npm1c-Driven Acute Myeloid Leukemia Cells

CRISPR-mediated MECOM depletion retards tumor growth by reducing cancer stem cell properties in lung squamous cell carcinoma

Targeted therapy for lung squamous cell carcinoma (LUSC) remains a challenge due to the lack of robust targets. Here, we identified MECOM as a candidate of therapeutic target for LUSC by screening 38 genes that were commonly amplified in three pairs of primary tumors and patient-derived xenografts (PDXs) using a clustered regularly interspaced short palindromic repeats (CRISPR)-mediated approach. High MECOM expression levels were associated with poor prognosis. Forced expression of MECOM in LUSC cell lines promoted cancer stem cell (CSC) properties, and its knockout inhibited CSC phenotypes. Furthermore, systemic delivery of CRISPR-mediated MECOM depletion cassette using adenovirus with an adaptor, which is composed of a single-chain fragment variable (scFv) against epithelial cell adhesion molecules (EpCAM) fused to the ectodomain of coxsackievirus and adenovirus receptor, and a protector, which consists of the scFv connected to the hexon symmetry of the adenovirus, could specifically target subcutaneous and orthotopic LUSC and retard tumor growth. This study could provide a novel therapeutic strategy for LUSC with high efficacy and specificity.

All-trans retinoic acid (ATRA) inhibits insufficient radiofrequency ablation (IRFA)-induced enrichment of tumor-initiating cells in hepatocellular carcinoma

OBJECTIVE

Local recurrence of hepatocellular carcinoma (HCC) after radiofrequency ablation (RFA) treatment remains a serious problem. Tumor-initiating cells (TICs) are thought to be responsible for tumor relapse. Here, we investigated the effect of the TIC differentiation inducer, all-trans retinoic acid (ATRA), on RFA and explored the potential molecular mechanisms.

METHODS

The proportions of CD133+ and epithelial cell adhesion molecule (EpCAM)+ TICs in recurrent HCC after RFA and primary HCC were first determined in clinic. Then, the effect of heat intervention or insufficient RFA (IRFA) on the malignant potential of HCC cells, including cell migration, sphere formation ability, tumor growth, the proportion of CD133+ and EpCAM+ TICs and expression of stem cell-related genes, was evaluated in vitro andin vivo. Finally, the effect of ATRA on the tumor growth and the proportion of TICs was evaluated.

RESULTS

In clinical data, a higher proportion of CD133+ and EpCAM+ TICs was found in recurrent tumors than in primary tumors. In vitro heat intervention promoted the cell migration and sphere formation ability. Additionally, it increased the proportion of CD133+ and EpCAM+ TICs and the expression of stem cell-related genes. In addition, after IRFA the residual tumors in xenografts grew faster and had more TICs than untreated tumors. ATRA remarkably inhibited residual tumor growth after IRFA by elimination of TICs though the PI3K/AKT pathway. Combination treatment with ATRA resulted in longer survival outcomes in mouse xenografts than RFA alone.

CONCLUSIONS

ATRA, as a TIC differentiation inducer, could help to improve the effect of RFA treatment, which was partially attributed to its effect against TICs. The data indicated its potential as an alternative drug in the development of better therapeutic strategies for use in combination with RFA.

All-trans retinoic acid induces differentiation in primary acute myeloid leukemia blasts carrying an inversion of chromosome 16

All-trans retinoic acid (ATRA)-based therapy for acute promyelocytic leukemia (APL), a subtype of acute myeloid leukemia (AML), is the most successful example of differentiation therapy. Although ATRA can induce differentiation in some non-APL AML cell lines and primary blasts, clinical results of adding ATRA to standard therapy in non-APL AML patients have been inconsistent, probably due to use of different regimens and lack of diagnostic tools for identifying which patients may be sensitive to ATRA. In this study, we exposed primary blasts obtained from non-APL AML patients to ATRA to test for differentiation potential in vitro. We observed increased expression of differentiation markers, indicating a response to ATRA, in four out of fifteen primary AML samples. Three samples in which CD11b increased in response to ATRA had an inversion of chromosome 16 as well as the CBFB-MYH11 fusion gene, and the fourth sample was from a patient with KMT2A-rearranged, therapy-related AML. In conclusion, we identified a subgroup of non-APL AML patients with inv(16) and CBFB-MYH11 as the most sensitive to ATRA-mediated differentiation in vitro, and our results can help identify patients who may benefit from ATRA treatment.

Therapeutic Use of Valproic Acid and All-Trans Retinoic Acid in Acute Myeloid Leukemia-Literature Review and Discussion of Possible Use in Relapse after Allogeneic Stem Cell Transplantation

Even though allogeneic stem cell transplantation is the most intensive treatment for acute myeloid leukemia (AML), chemo-resistant leukemia relapse is still one of the most common causes of death for these patients, as is transplant-related mortality, i.e., graft versus host disease, infections, and organ damage. These relapse patients are not always candidates for additional intensive therapy or re-transplantation, and many of them have decreased quality of life and shortened expected survival. The efficiency of azacitidine for treatment of posttransplant AML relapse has been documented in several clinical trials. Valproic acid is an antiepileptic fatty acid that exerts antileukemic activity through histone deacetylase inhibition. The combination of valproic acid and all-trans retinoic acid (ATRA) is well tolerated even by unfit or elderly AML patients, and low-toxicity chemotherapy (e.g., azacitidine) can be added to this combination. The triple combination of azacitidine, valproic acid, and ATRA may therefore represent a low-intensity and low-toxicity alternative for these patients. In the present review, we review and discuss the general experience with valproic acid/ATRA in AML therapy and we discuss its possible use in low-intensity/toxicity treatment of post-allotransplant AML relapse. Our discussion is further illustrated by four case reports where combined treatments with sequential azacitidine/hydroxyurea, valproic acid, and ATRA were used.