Chemosensitization by 4-hydroxyphenyl retinamide-induced NF-κB inhibition in acute myeloid leukemia cells

Nano-fenretinide demonstrates remarkable activity in acute promyeloid leukemia cells

Acute promyelocytic leukemia (APL) is characterized by rearrangements of the retinoic acid receptor, RARα, which makes all-trans retinoic acid (ATRA) highly effective in the treatment of this disease, inducing promyelocytes differentiation. Current therapy, based on ATRA in combination with arsenic trioxide, with or without chemotherapy, provides high rates of event-free survival and overall survival. However, a decline in the drug activity, due to increased ATRA metabolism and RARα mutations, is often observed over long-term treatments. Furthermore, dedifferentiation can occur providing relapse of the disease. In this study we evaluated fenretinide, a semisynthetic ATRA derivative, encapsulated in nanomicelles (nano-fenretinide) as an alternative treatment to ATRA in APL. Nano-fenretinide was prepared by fenretinide encapsulation in a self-assembling phospholipid mixture. Physico-chemical characterization was carried out by dinamic light scattering and spectrophotometry. The biological activity was evaluated by MTT assay, flow cytometry and confocal laser-scanning fluorescence microscopy. Nano-fenretinide induced apoptosis in acute promyelocytic leukemia cells (HL60) by an early increase of reactive oxygen species and a mitochondrial potential decrease. The fenretinide concentration that induced 90-100% decrease in cell viability was about 2.0 µM at 24 h, a concentration easily achievable in vivo when nano-fenretinide is administered by oral or intravenous route, as demonstrated in previous studies. Nano-fenretinide was effective, albeit at slightly higher concentrations, also in doxorubicin-resistant HL60 cells, while a comparison with TK6 lymphoblasts indicated a lack of toxicity on normal cells. The results indicate that nano-fenretinide can be considered an alternative therapy to ATRA in acute promyelocytic leukemia when decreased efficacy, resistance or recurrence of disease emerge after protracted treatments with ATRA.

Natural medicinal compounds target signal transduction pathways to overcome ABC drug efflux transporter-mediated multidrug resistance in cancer

ATP-binding cassette (ABC) transporters such as ABCB1, ABCG2, and ABCC1 are the major players in drug efflux-mediated multidrug resistance (MDR), which severely affects the efficacy of chemotherapy. Several synthetic compounds block the drug transport by ABC transporters; however, they exhibit a narrow therapeutic window, and produce side effects in non-target normal tissues. Conversely, the downregulation of the expression of ABC drug transporters seems to be a promising strategy to reverse MDR in cancer cells. Several signaling pathways, such as NF-κB, STAT3, Gli, NICD, YAP/TAZ, and Nrf2 upregulate the expression of ABC drug transporters in drug-resistant cancers. Recently, natural medicinal compounds have gained importance to overcome the ABC drug-efflux pump-mediated MDR in cancer. These compounds target transcription factors and the associated signal transduction pathways, thereby downregulating the expression of ABC transporters in drug-resistant cancer cells. Several potent natural compounds have been identified as lead candidates to synergistically enhance chemotherapeutic efficacy, and a few of them are already in clinical trials. Therefore, modulation of signal transduction pathways using natural medicinal compounds for the reversal of ABC drug transporter-mediated MDR in cancer is a novel approach for improving the efficiency of the existing chemotherapeutics. In this review, we discuss the modulatory role of natural medicinal compounds on cellular signaling pathways that regulate the expression of ABC transporters in drug-resistant cancer cells.

TRIM10 Is Downregulated in Acute Myeloid Leukemia and Plays a Tumor Suppressive Role via Regulating NF-κB Pathway

BACKGROUND

Accumulating evidence suggests that members of the tripartite motif (TRIMs) family play a crucial role in the development and progression of hematological malignancy. Here, we explored the expression and potential role of TRIM10 in acute myeloid leukemia (AML).

METHODS

The expression levels of TRIM10 were investigated in AML patients and cell lines by RNA-seq, qRT-PCR and Western blotting analysis. Lentiviral infection was used to regulate the level of TRIM10 in AML cells. The effects of TRIM10 on apoptosis, drug sensitivity and proliferation of AML cells were evaluated by flow cytometry and cell-counting kit-8 (CCK-8) assay, as well as being assessed in a murine model.

RESULTS

TRIM10 mRNA and protein expression was reduced in primary AML samples and AML cell lines in comparison to the normal controls and a human normal hematopoietic cell line, respectively. Moreover, overexpression of TRIM10 in HL60 and K562 cells inhibited AML cell proliferation and induced cell apoptosis. The nude mice study further confirmed that overexpression of TRIM10 blocked tumor growth and inhibited cell proliferation. In contrast, knockdown of TRIM10 in AML cells showed contrary results. Subsequent mechanistic studies demonstrated that knockdown of TRIM10 enhanced the expression of nuclear protein P65, which implied the activation of the NF-κB signal pathway. Consistently, overexpression of TRIM10 in AML cells showed a contrary result. These data indicated that inactivation of the NF-κB pathway is involved in TRIM10-mediated regulation in AML. TRIM10 expression can be de-repressed by a combination that targets both DNA methyltransferase and histone deacetylase.

CONCLUSIONS

Our results strongly suggested that TRIM10 plays a tumor suppressive role in AML development associated with the NF-κB signal pathway and may be a potential target of epigenetic therapy against leukemia.

Advancements on the Multifaceted Roles of Sphingolipids in Hematological Malignancies

Dysregulation of sphingolipid metabolism plays a complex role in hematological malignancies, beginning with the first historical link between sphingolipids and apoptosis discovered in HL-60 leukemic cells. Numerous manuscripts have reviewed the field including the early discoveries that jumpstarted the studies. Many studies discussed here support a role for sphingolipids, such as ceramide, in combinatorial therapeutic regimens to enhance anti-leukemic effects and reduce resistance to standard therapies. Additionally, inhibitors of specific nodes of the sphingolipid pathway, such as sphingosine kinase inhibitors, significantly reduce leukemic cell survival in various types of leukemias. Acid ceramidase inhibitors have also shown promising results in acute myeloid leukemia. As the field moves rapidly, here we aim to expand the body of literature discussed in previously published reviews by focusing on advances reported in the latter part of the last decade.