RAB27B inhibits proliferation and promotes apoptosis of leukemic cells via 3-Hydroxy butyrate dehydrogenase 2 (BDH2)

Impact of Rab27 on Melanoma Cell Invasion and sEV Secretion

The migratory and invasive capabilities of melanoma cells contribute to metastasis. Therefore, targeting the genes driving these processes can support melanoma therapy. Rab27A and Rab27B contribute to tumor formation progression in many types of cancer through various mechanisms, including the secretion of small extracellular vesicles (sEVs). We explored the role of these GTPases in melanoma cell functioning in three RAB27A knockout (KO) cell lines (A375, DMBC12, and SkMel28) and a double RAB27A/B KO A375 cell line. The loss of RAB27A impaired the migration and invasion of DMBC12 and SkMel28 cells; however, the behavior of highly aggressive A375 cells was unaffected. The RAB27A/B double knockout moderately decreased the migratory capacity of A375 cells without disturbing their invasiveness. Additionally, the silencing of RAB27A did not affect the number and mean size of the sEVs, despite some alterations in the protein content of the vesicles. Both Rab27 isoforms can, at least partially, act independently. The potential role of Rab27A in the functioning of melanoma cells depends on the individual character of the cell line, but not on its basal expression, and seems to be unrelated to the secretion of sEVs.

Lipopolymer/siRNA complexes engineered for optimal molecular and functional response with chemotherapy in FLT3-mutated acute myeloid leukemia

Approximately 25% of newly diagnosed AML patients display an internal tandem duplication (ITD) in the fms-like tyrosine kinase 3 (FLT3) gene. Although both multi-targeted and FLT3 specific tyrosine kinase inhibitors (TKIs) are being utilized for clinical therapy, drug resistance, short remission periods, and high relapse rates are challenges that still need to be tackled. RNA interference (RNAi), mediated by short interfering RNA (siRNA), presents a mechanistically distinct therapeutic platform with the potential of personalization due to its gene sequence-driven mechanism of action. This study explored the use of a non-viral approach for delivery of FLT3 siRNA (siFLT3) in FLT3-ITD positive AML cell lines and primary cells as well as the feasibility of combining this treatment with drugs currently used in the clinic. Treatment of AML cell lines with FLT3 siRNA nanocomplexes resulted in prominent reduction in cell proliferation rates and induction of apoptosis. Quantitative analysis of relative mRNA transcript levels revealed downregulation of the FLT3 gene, which was accompanied by a similar decline in FLT3 protein levels. Moreover, an impact on leukemic stem cells was observed in a small pool of primary AML samples through significantly reduced colony numbers. An absence of a molecular response post-treatment with lipopolymer/siFLT3 complexes in peripheral blood mononuclear cells, obtained from healthy individuals, denoted a passive selectivity of the complexes towards malignant cells. The effect of combining lipopolymer/siFLT3 complexes with daunorubucin and FLT3 targeting TKI gilteritinib led to a significant augmentation of anti-leukemic activity. These findings demonstrate the promising potential of RNAi implemented with lipopolymer complexes for AML molecular therapy. The study prospectively supports the addition of RNAi therapy to current treatment modalities available to target the heterogeneity prevalent in AML. STATEMENT OF SIGNIFICANCE: We show that a clinically validated target, the FLT3 gene, can be eradicated in leukemia cells using non-viral RNAi. We validated these lipopolymers as effective vehicles to deliver nucleic acids to leukemic cells. The potency of the lipopolymers was superior to that of the 'gold-standard' delivery agent, lipid nanoparticles (LNPs), which are not effective in leukemia cells at clinically relevant doses. Mechanistic studies were undertaken to probe structure-function relationships for effective biomaterial formulations. Cellular and molecular responses to siRNA treatment have been characterized in cell models, including leukemia patient-derived cells. The use of the siRNA therapy with clinically used chemotherapy was demonstrated.

Use of extracellular vesicle microRNA profiles in patients with acute myeloid leukemia for the identification of novel biomarkers

OBJECTIVES

This study aimed to establish clinically significant microRNA (miRNA) sets using extracellular vesicles (EVs) from bone marrow (BM) aspirates of patients with acute myelogenous leukemia (AML), and to identify the genes that interact with these EV-derived miRNAs in AML.

MATERIALS AND METHODS

BM aspirates were collected from 32 patients with AML at the time of AML diagnosis. EVs were isolated using size-exclusion chromatography. A total of 965 EV-derived miRNAs were identified in all the samples.

RESULTS

We analyzed the expression levels of these EV-derived miRNAs of the favorable (n = 10) and non-favorable (n = 22) risk groups; we identified 32 differentially expressed EV-derived miRNAs in the non-favorable risk group. The correlation of these miRNAs with risk stratification and patient survival was analyzed using the information of patients with AML from The Cancer Genome Atlas (TCGA) database. Of the miRNAs with downregulated expression in the non-favorable risk group, hsa-miR-181b and hsa-miR-143 were correlated with non-favorable risk and short overall survival. Regarding the miRNAs with upregulated expression in the non-favorable risk group, hsa-miR-188 and hsa-miR-501 were correlated with non-favorable risk and could predict poor survival. Through EV-derived miRNAs-mRNA network analysis using TCGA database, we identified 21 mRNAs that could be potential poor prognosis biomarkers.

CONCLUSIONS

Overall, our findings revealed that EV-derived miRNAs can serve as biomarkers for risk stratification and prognosis in AML. In addition, these EV-derived miRNA-based bioinformatic analyses could help efficiently identify mRNAs with biomarker potential, similar to the previous cell-based approach.

Linking pesticide exposure to neurodegenerative diseases: An in vitro investigation with human neuroblastoma cells

Although many organochlorine pesticides (OCPs) have been banned or restricted because of their persistence and linkage to neurodegenerative diseases, there is evidence of continued human exposure. In contrast, registered herbicides are reported to have a moderate to low level of toxicity; however, there is little information regarding their toxicity to humans or their combined effects with OCPs. This study aimed to characterize the mechanism of toxicity of banned OCP insecticides (aldrin, dieldrin, heptachlor, and lindane) and registered herbicides (trifluralin, triallate, and clopyralid) detected at a legacy contaminated pesticide manufacturing and packing site using SH-SY5Y cells. Cell viability, LDH release, production of reactive oxygen species (ROS), and caspase 3/7 activity were evaluated following 24 h of exposure to the biocides. In addition, RNASeq was conducted at sublethal concentrations to investigate potential mechanisms involved in cellular toxicity. Our findings suggested that aldrin and heptachlor were the most toxic, while dieldrin, lindane, trifluralin, and triallate exhibited moderate toxicity, and clopyralid was not toxic to SH-SY5Y cells. While aldrin and heptachlor induced their toxicity through damage to the cell membrane, the toxicity of dieldrin was partially attributed to necrosis and apoptosis. Moreover, toxic effects of lindane, trifluralin, and triallate, at least partially, were associated with ROS generation. Gene expression profiles suggested that decreased cell viability induced by most of the tested biocides was related to inhibited cell proliferation. The dysregulation of genes encoding for proteins with anti-apoptotic properties also supported the absence of caspase activation. Identified enriched terms showed that OCP toxicity in SH-SY5Y cells was mediated through pathways associated with the pathogenesis of neurodegenerative diseases. In conclusion, this study provides a basis for elucidating the molecular mechanisms of pesticide-induced neurotoxicity. Moreover, it introduced SH-SY5Y cells as a relevant in vitro model for investigating the neurotoxicity of pesticides in humans.

Rab27b promotes endometriosis by enhancing invasiveness of ESCs and promoting angiogenesis

PROBLEM

Endometriosis (EMS) is an estrogen-dependent disease which is characterized with estrogen-dependent growth of ectopic endometrium and increased local estrogen production. EMS performs tumor-like biological functions such as invasiveness and angiogenesis. Rab27b is a member of the Rab family of GTPases, which is strongly associated with the growth, invasion and metastasis of a variety of tumors. However, little is known about the function of Rab27b in EMS. In this study, we intended to investigate the impact of Rab27b and its downstream molecule in the development of EMS.

METHOD OF STUDY

Normal endometrium and endometriotic lesions were collected to investigate the expression levels of Rab27b. Then, ESCs were transfected with Rab27b siRNA. We analyzed the influence of Rab27b on the proliferation and invasive activity of ESCs. Conditioned media harvested from Rab27b siRNA-treated ESCs were used to treat HUVECs. HUVEC Tube formation and ELISA were performed to explored the interactions between ESCs and HUVEC. In addition, ESCs were treated with different concentrations of estrogen. Based on biological database predictions, we explored possible mechanisms through which estrogen regulates the expression of Rab27b.

RESULTS

The expressions of Rab27b were significantly higher in endometriotic lesions than that in normal endometrium. Rab27b can promote the cell proliferation, migration and invasion of ESCs. The elevated expression of Rab27b, on the one hand, promotes the secretion of MMP9 and increases the invasiveness of ESCs. On the other hand, Rab27b may play a key role in the communication between ESC and endothelial cells, by simulating VEGF secretion and neovascularization. Besides, estrogen upregulated phosphorylated FOXO1 levels in ectopic ESCs, resulting in the promotion of Rab27b expression levels.

CONCLUSION

Rab27b plays a key role in the development of EMS, which may provide new insights into the pathogenesis of EMS. Our findings may also contribute to the development of therapeutic interventions for EMS.

RAB27B controls palmitoylation-dependent NRAS trafficking and signaling in myeloid leukemia

RAS mutations are among the most prevalent oncogenic drivers in cancers. RAS proteins propagate signals only when associated with cellular membranes as a consequence of lipid modifications that impact their trafficking. Here, we discovered that RAB27B, a RAB family small GTPase, controlled NRAS palmitoylation and trafficking to the plasma membrane, a localization required for activation. Our proteomic studies revealed RAB27B upregulation in CBL- or JAK2-mutated myeloid malignancies, and its expression correlated with poor prognosis in acute myeloid leukemias (AMLs). RAB27B depletion inhibited the growth of CBL-deficient or NRAS-mutant cell lines. Strikingly, Rab27b deficiency in mice abrogated mutant but not WT NRAS-mediated progenitor cell growth, ERK signaling, and NRAS palmitoylation. Further, Rab27b deficiency significantly reduced myelomonocytic leukemia development in vivo. Mechanistically, RAB27B interacted with ZDHHC9, a palmitoyl acyltransferase that modifies NRAS. By regulating palmitoylation, RAB27B controlled c-RAF/MEK/ERK signaling and affected leukemia development. Importantly, RAB27B depletion in primary human AMLs inhibited oncogenic NRAS signaling and leukemic growth. We further revealed a significant correlation between RAB27B expression and sensitivity to MEK inhibitors in AMLs. Thus, our studies presented a link between RAB proteins and fundamental aspects of RAS posttranslational modification and trafficking, highlighting future therapeutic strategies for RAS-driven cancers.

Long noncoding RNA (lncRNA) metallothionein 1 J, pseudogene (MT1JP) is downregulated in triple-negative breast cancer and upregulates microRNA-138 (miR-138) to downregulate hypoxia-inducible factor-1α (HIF-1α)

Triple-negative breast cancer (TNBC) is a highly invasive subtype of breast cancer. This study explored the molecular mechanism and influences of metallothionein 1 J, pseudogene (MT1JP), microRNA-138 (miR-138), and hypoxia-inducible factor-1α (HIF-1α) on TNBC cell proliferation and migration. We confirmed TNBC cases by immunohistochemistry (IHC) staining. The expression of MT1JP in two types of tissue collected from 78 TNBC patients was detected by performing real-time quantitative fluorescence PCR (RT-qPCR). To further evaluate the relationship among MT1JP, miR-138 and HIF-1α, expression vectors of MT1JP and HIF-1α, as well as miR-138 mimic and inhibitor, were delivered into BT-549 cells. We observed that MT1JP was downregulated in TNBC. MT1JP was positively correlated with miR-138 but negatively correlated with HIF-1α in TNBC tissues. In TNBC cells, upregulation of miR-138 and downregulation of HIF-1α were observed after overexpression of MT1JP. In addition, overexpression of miR-138 resulted in downregulation of HIF-1α but did not affect the expression of MT1JP. Decreased proliferation rate of TNBC cells was observed after overexpression of MT1JP and miR-138. HIF-1α increased cell proliferation and migration. HIF-1α also suppressed the role of MT1JP and miR-138 in TNBC cell proliferation and migration. In conclusion, our findings demonstrated that MT1JP inhibited TNBC by regulating the miR-138/HIF-1α axis, indicating that MT1JP might serve as a biomarker or target for TNBC treatment.