Internal tandem duplication within FLT3 (FLT3-ITD) is one of the most frequent mutations in acute myeloid leukemia (AML) and correlates with a poor prognosis. Whereas the FLT3 receptor tyrosine kinase is activated at the plasma membrane to transduce PI3K/AKT and RAS/MAPK signaling, FLT3-ITD resides in the endoplasmic reticulum and triggers constitutive STAT5 phosphorylation. Mechanisms underlying this aberrant FLT3-ITD subcellular localization or its impact on leukemogenesis remain poorly established. In this study, we discovered that FLT3-ITD is S-palmitoylated by the palmitoyl acyltransferase ZDHHC6. Disruption of palmitoylation redirected FLT3-ITD to the plasma membrane and rewired its downstream signaling by activating AKT and extracellular signal-regulated kinase pathways in addition to STAT5. Consequently, abrogation of palmitoylation increased FLT3-ITD–mediated progression of leukemia in xenotransplant-recipient mouse models. We further demonstrate that FLT3 proteins were palmitoylated in primary human AML cells. ZDHHC6-mediated palmitoylation restrained FLT3-ITD surface expression, signaling, and colonogenic growth of primary FLT3-ITD+ AML. More important, pharmacological inhibition of FLT3-ITD depalmitoylation synergized with the US Food and Drug Administration–approved FLT3 kinase inhibitor gilteritinib in abrogating the growth of primary FLT3-ITD+ AML cells. These findings provide novel insights into lipid-dependent compartmentalization of FLT3-ITD signaling in AML and suggest targeting depalmitoylation as a new therapeutic strategy to treat FLT3-ITD+ leukemias.

Oral squamous cell carcinoma (OSCC) is the most prevalent subtype of head and neck tumors, highly prone to lymph node metastasis. This study aims to examine the expression pattern of Ras-related protein Rab-27A (RAB27A) and explore its potential implications in OSCC. The expression of RAB27A was assessed through immunohistochemical analysis utilizing tissue microarrays. In vitro experiments were conducted using RAB27A-knockdown cells to investigate its impact on OSCC tumor cells. Additionally, transcriptome sequencing was performed to elucidate potential underlying mechanisms. RAB27A was significantly overexpressed in OSCC, and particularly in metastatic lymph nodes. It was positively correlated with the clinical progression and poor survival prognosis. Silencing RAB27A notably decreased the proliferation, migration, and invasion abilities of OSCC cells in vitro. A Gene Ontology (GO) enrichment analysis indicated a strong association between RAB27A and the epidermal growth factor receptor (EGFR) signaling pathway. Further investigations revealed that RAB27A regulated the palmitoylation of EGFR via zinc finger DHHC-type containing 13 (ZDHHC13). These findings provide insights into OSCC progression and highlight RAB27A as a potential therapeutic target for combating this aggressive cancer.

Oral epithelial adhesion to the lamina propria underlies the physiologic function of the oral mucosa and contributes to resisting bacterial invasion, preventing body fluid loss, and maintaining routine chewing; thus, understanding the factors that positively influence oral epithelial adhesion is a research topic of great interest. Rete pegs contribute to oral epithelial adhesion by enlarging the contact areas, whereas integrins are the major molecules that mediate epithelial cell adhesion to the basement membrane. Keratinocyte growth factor (KGF) can promote both rete peg elongation in the skin and the expression of integrins in various cell types. Herein, we tested the effects of submucosal injection of KGF in the ventral surfaces of rat tongues on oral epithelial adhesion. The data confirmed that topical injection of KGF elevated the adhesive forces, elongated the rete pegs, and increased the abundance of integrins, KGF, and KGF receptor on the rat tongue ventral surface. However, HYD-1 (Lys-Ile-Lys-Met-Val-Ile-Ser-Trp-Lys-Gly), an integrin antagonist, inhibited the KGF-enhanced epithelial adhesion and rete peg elongation. Moreover, KGF promoted the expression of integrin subunits α6, β4, α3, and β1 in human immortalized oral epithelial cells in 2- and 3-dimensional culture systems. In vitro cell attachment assays demonstrated that HYD-1 inhibited the adhesion of human immortalized oral epithelial cells on Matrigel. Strikingly, the expression of integrins, KGF, and KGFR in human masticatory mucosae with longer rete pegs was more abundant than that in the lining mucosae with shorter rete pegs. In addition, rete peg lengths were positively correlated with the expression levels of integrins, KGF, and KGF receptor. These findings indicate that KGF strengthens oral epithelial adhesion and rete peg elongation via integrins.

N6-methyladenosine (m⁶A) is the most abundant RNA modification, regulating gene expression in physiological processes. However, its effect on the osteogenic differentiation of dental follicle stem cells (DFSCs) remains unknown. Here, m⁶A demethylases, the fat mass and obesity-associated protein (FTO), and alkB homolog 5 (ALKBH5) were overexpressed in DFSCs, followed by osteogenesis assay and transcriptome sequencing to explore potential mechanisms. The overexpression of FTO or ALKBH5 inhibited the osteogenesis of DFSCs, evidenced by the fact that RUNX2 independently decreased calcium deposition and by the downregulation of the osteogenic genes OCN and OPN. MiRNA profiling revealed that miR-7974 was the top differentially regulated gene, and the overexpression of m⁶A demethylases significantly accelerated miR-7974 degradation in DFSCs. The miR-7974 inhibitor decreased the osteogenesis of DFSCs, and its mimic attenuated the inhibitory effects of FTO overexpression. Bioinformatic prediction and RNA sequencing analysis suggested that FK506-binding protein 15 (FKBP15) was the most likely target downstream of miR-7974. The overexpression of FKBP15 significantly inhibited the osteogenesis of DFSCs via the restriction of actin cytoskeleton organization. This study provided a data resource of differentially expressed miRNA and mRNA after the overexpression of m⁶A demethylases in DFSCs. We unmasked the RUNX2-independent effects of m⁶A demethylase, miR-7974, and FKBP15 on the osteogenesis of DFSCs. Moreover, the FTO/miR-7974/FKBP15 axis and its effects on actin cytoskeleton organization were identified in DFSCs.