Long Non-Coding RNA Nuclear-Enriched Abundant Transcript 1 (NEAT1) Facilitates Foam Cell Formation and Atherosclerosis Progression Through the miR-17-5p/Itchy E3 Ubiquitin Protein Ligase (ITCH)/Liver Kinase B1 (LKB1) Axis

BACKGROUND

Foam cell formation is an important step for atherosclerosis (AS) progression. We investigated the mechanism by which the long non-coding RNA (lncRNA) nuclear-enriched abundant transcript 1 (NEAT1) regulates foam cell formation during AS progression.Methods and Results: An in vivo AS model was created by feeding ApoE-/-mice a high-fat diet. Oxidized low-density lipoprotein (ox-LDL)-stimulated macrophages were used as a cellular AS model. Interactions between NEAT1, miR-17-5p, itchy E3 ubiquitin protein ligase (ITCH) and liver kinase B1 (LKB1) were analyzed. NEAT1 and ITCH were highly expressed in clinical samples collected from 10 AS patients and in ox-LDL-treated macrophages, whereas expression of both miR-17-5p and LKB1 was low. ITCH knockdown inhibited ox-LDL-induced lipid accumulation and LDL uptake in macrophages. Mechanistically speakingly, ITCH promoted LDL uptake and lipid accumulation in macrophages by mediating LKB1 ubiquitination degradation. NEAT1 knockdown reduced LDL uptake and lipid accumulation in macrophages and AS progression in vivo. NEAT1 promoted ITCH expression in macrophages by acting as a sponge for miR-17-5p. Inhibition of miR-17-5p facilitated ox-LDL-induced increase in LDL uptake and lipid accumulation in macrophages, which was reversed by NEAT1/ITCH knockdown.

CONCLUSIONS

NEAT1 accelerated foam cell formation during AS progression through the miR-17-5p/ITCH/LKB1 axis.

Potential role of CXCR4 in trastuzumab resistance in breast cancer patients

Despite the efficacy of trastuzumab in treating HER2-positive breast cancer patients, a significant proportion of patients relapse after treatment. The role of C-X-C chemokine receptor type 4 (CXCR4) in trastuzumab resistance was studied only in cell lines and the underlying mechanisms remain largely unclear. This study investigated the role of CXCR4 in trastuzumab resistance in breast cancer patients and explored the possible underlying mechanisms. The study was performed retrospectively on tissue samples from 62 breast cancer patients including 42 who were treated with trastuzumab and chemotherapy and 20 who received chemotherapy alone in adjuvant setting. Expression levels of CXCR4 and its regulators hypoxia-inducible factor 1-alpha (HIF-1α), tristetraprolin (TTP), human antigen R (HuR), itchy E3 ubiquitin protein ligase (ITCH), miR-302a and miR-494 were determined and their associations with tumor recurrence and disease-free survival were analyzed. In trastuzumab-treated patients, high CXCR4 expression was associated with recurrence and was an independent predictor of progression risk after therapy. CXCR4 correlated positively with its transcriptional regulator, HIF-1α, and negatively with its post-translational regulator, ITCH. HIF-1α, HuR and ITCH were significantly associated with clinical outcome. In chemotherapy-treated patients, neither CXCR4 nor any of its regulators were associated with recurrence or predicted disease progression risk after chemotherapy. In conclusion, this study suggests a potential role for CXCR4 in recurrence after trastuzumab-based therapy in human breast cancer that could be mediated, at least in part, by hypoxia and/or decreased ubiquitination. These findings highlight the potential utility of CXCR4 as a promising target for enhancing trastuzumab therapeutic outcome.