ULK2

To investigate the role and molecular mechanism of exosomal miR-224-5p in colorectal cancer (CRC).

The miR-224-5p expression in CRC patient tissues and cell-derived exosomes was measured by laser capture microdissection and qRT-PCR, respectively. Dual-luciferase reporter gene assay was used to determine the target gene of miR-224-5p. The protein expressions of p53 and unc-51 like kinase 2 (ULK2) in CRC cells were detected by western blot. Flow cytometry was used to detect cell cycle and apoptosis. Cell proliferation was measured by CCK8 and EdU assay.

The miR-224-5p expression was upregulated in CRC tissues and increased progressively with the rise of CRC stage. CRC cells secreted extracellular miR-224-5p mainly in an exosome-dependent manner, and then miR-224-5p could be transferred to surrounding tumor cells to regulate cell proliferation in the form of autocrine or paracrine. Moreover, ULK2 was characterized as a direct target of miR-224-5p and was downregulated in CRC tissues. Interestingly, ULK2 inhibited CRC cell proliferation in a p53-dependent manner. Furthermore, exosome-derived miR-224-5p partially reversed the proliferation regulation of ULK2 on CRC cells.

Our findings demonstrate that exosome-transmitted miR-224-5p promotes p53-dependent cell proliferation by targeting ULK2 in CRC, which may offer promising targets for CRC prevention and therapy.

We recently demonstrated that a small subset of cells in FLT3-mutated acute myeloid leukemia (AML) cell lines exhibit SORE6 reporter activity and cancer stem-like features including chemoresistance. To study why SORE6⁺ cells are more chemoresistant than SORE6^- cells, we hypothesized that these cells carry higher autophagy, a mechanism linked to chemoresistance. We found that cytarabine (Ara-C) induced a substantially higher protein level of LC3B-II in SORE6⁺ compared to SORE6^- cells. Similar observations were made using a fluorescence signal-based autophagy assay. Furthermore, chloroquine (an autophagy inhibitor) sensitized SORE6⁺ but not SORE6^- cells to Ara-C. To decipher the molecular mechanisms underlying the high autophagic flux in SORE6⁺ cells, we employed an autophagy oligonucleotide array comparing gene expression between SORE6⁺ and SORE6^- cells before and after Ara-C treatment. ULK2 was the most differentially expressed gene between the two cell subsets. To demonstrate the role of ULK2 in conferring higher chemoresistance in SORE6⁺ cells, we treated the two cell subsets with a ULK1/2 inhibitor, MRT68921. MRT68921 significantly sensitized SORE6⁺ but not SORE6^- cells to Ara-C. Using our in vitro model for AML relapse, we found that regenerated AML cells contained higher ULK2 expression compared to pretreated cells. Importantly, inhibition of ULK2 using MRT68921 prevented in vitro AML relapse. Lastly, using pretreatment and relapsed AML patient bone marrow samples, we found that ULK2 expression was higher in relapsed AML. To conclude, our results supported the importance of autophagy in the relapse of FLT3-mutated AML and highlighted ULK2 in this context.

High-grade gliomas are extremely fatal tumors, marked by severe hypoxia and therapeutic resistance. Autophagy is a cellular degradative process that can be activated by hypoxia, ultimately resulting in tumor advancement and chemo-resistance. Our study aimed to examine the link between autophagy markers' expression in low-grade gliomas (LGGs) and high-grade gliomas (HGGs). In 39 glioma cases, we assessed the protein expression of autophagy markers LC3B, SQSTM1/p62, and DRAM by immunohistochemistry (IHC) and the mRNA expression of the autophagy genes PTEN, PI3K, AKT, mTOR, ULK1, ULK2, UVRAG, Beclin 1, and VPS34 using RT-qPCR. LC3B, SQSTM1/p62, and DRAM expression were positive in 64.1%, 51.3%, and 28.2% of glioma cases, respectively. The expression of LC3B and SQSTM1/p62 was notably higher in HGGs compared to LGGs. VPS34 exhibited a significant differential expression, displaying increased fold change in HGGs compared to LGGs. Additionally, it exhibited robust positive associations with Beclin1 (rs = 0.768), UVRAG (rs = 0.802), and ULK2 (rs = 0.786) in HGGs. This underscores a potential association between autophagy and the progression of gliomas. We provide preliminary data for the functional analysis of autophagy using a cell culture model and to identify potential targets for therapeutic interventions.