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Intraseasonal variabilities (ISVs) of the western boundary currents (WBCs) east of Luzon Island were explored using acoustic Doppler current profiler (ADCP) measurements from three moorings at 18°N during 2018–2020. Besides the traditionally known surface‐intensified ISV, subsurface‐intensified ISV with a typical period of approximately 60 days was also detected in the currents, and the strongest signal appeared between 400 and 800 m. Further analysis indicates that they are highly associated with subsurface eddies. Based on their lifespan, subsurface eddies are classified into two categories: short‐lived and medium‐to long‐lived eddies. The short‐lived eddies are primarily generated locally near the eastern coast of Luzon Island, whereas the medium‐to long‐lived eddies are mainly generated away from the western boundary, in the region west of 135°E. Additional energy diagnosis suggests that baroclinic instability induced by the velocity shear of the North Equatorial Current (NEC)/subtropical countercurrent (STCC) system dominates the generation of medium‐to long‐lived subsurface eddies in the interior ocean, while barotropic instability and baroclinic instability play a comparable role in the generation of short‐lived eddies near the eastern coast of Luzon Island. Plain Language Summary: The Kuroshio and Luzon Undercurrent (LUC) have a far‐reaching impact on regional climate change as a crucial part of the western boundary current (WBC) system. In situ measurements east of Luzon Island have revealed that the currents exhibit significant intraseasonal variabilities (ISVs). However, the vertical difference of the ISVs is unclear, and we still do not know if subsurface ISVs exist in this region. In this work, we found the currents east of Luzon Island are characterized by two types of ISVs with a period of approximately 60 days: surface‐intensified and subsurface‐intensified. The two types of ISVs are linked to the surface and subsurface mesoscale eddies, respectively. Previous studies have revealed that baroclinic instability associated with the vertical shear of velocity in the North Equatorial Current/subtropical countercurrent (NEC/STCC) system is the primary generation mechanism of surface eddies. This study suggests that baroclinic instability of the NEC/STCC system also dominates the generation of subsurface eddies in the interior ocean, while barotropic instability associated with the horizontal shear of currents near the Luzon coast is non‐negligible in the generation of coastal subsurface eddies. These results significantly deepen our understanding of the ISVs of the currents in this region. Key Points: Quasi‐60‐day intraseasonal variability in the currents east of Luzon Island exhibits surface‐ and subsurface‐intensified vertical featuresSubsurface‐intensified eddies are revealed appearing east of Luzon Island and modulating the western boundary currentsBaroclinic instability dominates the generation of subsurface eddies east of Luzon while coastal barotropic instability is non‐negligible [ABSTRACT FROM AUTHOR]

Interannual variation of subthermocline eddy kinetic energy (EKE) east of the Philippines is investigated based on mooring measurements during 2015–2019 and ocean‐state estimates during 1995–2017 from the Oceanic General Circulation Model for the Earth Simulator (OFES). Prominent interannual variation of EKE is detected below the thermocline east of the Philippine coast, which is closely related to the El Niño and Southern Oscillation (ENSO) events and generally lags the Nino3.4 index by 14 months. Further energy diagnostic analysis indicates that the interannual variation of subthermocline EKE is controlled by both baroclinic and barotropic instability of the background flows and dominated by the barotropic instability especially. Barotropic instability in the southern part of the Philippine coast is associated with the subsurface component of the quasi‐permanent anticyclonic Halmahera Eddy (HE), while that in the northern part is closely related to the Mindanao Undercurrent (MUC). Both HE and MUC are modulated by the ENSO events. When El Niño occurs, negative sea surface height anomalies appear near the dateline and propagate westward in the form of the first‐mode baroclinic Rossby wave, exerting delayed impacts upon the western boundary currents east of the Philippine coast and further modulating the interannual variation of subthermocline EKE. Moreover, the barotropic energy conversion rate and its corresponding subthermocline EKE at lower latitudes respond relatively faster to ENSO due to the higher Rossby wave group velocity there. Plain Language Summary: Subthermocline mesoscale eddies that have velocity core below the thermocline with almost no signal at the sea surface are distributed widely over the world oceans and play a crucial role in the transport of subsurface waters. The region east of the Philippine coast features energetic eddies and high eddy kinetic energy (EKE) in the subsurface layer. These eddies are intrinsic to the ocean and extract energy from the background currents. Based on 4‐year mooring measurements and numerical model outputs during 1995–2017, strong interannual variation of subthermocline EKE is detected in this region. Further analysis demonstrates that this interannual variation is mainly modulated by the evolution of barotropic instability, which represents the energy flux between the mean kinetic energy and EKE associated with the background flows. Additionally, the interannual variation of subthermocline EKE seems to be influenced by El Niño and Southern Oscillation. The wind anomalies associated with El Niño events excite negative sea surface height anomalies near the dateline, which propagate westward in the form of Rossby wave, producing delayed impacts on the western boundary currents and then on the variation of subthermocline EKE. This work enriches our knowledge of the low‐frequency modulation of subthermocline EKE in this region. Key Points: Significant interannual variation of subthermocline eddy kinetic energy (EKE) related to ENSO is detected east of the Philippines with mooring and modelModel shows that both barotropic and baroclinic instability are responsible for interannual EKE variation, and barotropic factor is dominantInterannual modulation of barotropic instability is associated with the variation of Mindanao Undercurrent and Halmahera Eddy [ABSTRACT FROM AUTHOR]

Mounting evidence has indicated that aberrantly expressed microRNAs (miRNAs) play key roles in tumorigenesis, including in head and neck squamous cell carcinoma (HNSCC). Previous studies have shown that miR‐335‐5p can serve as a tumor suppressor or an oncogene in cancer. However, the clinical importance and biological effects of miR‐335‐5p in HNSCC have not been determined. Here, we investigated the expression pattern, functional role, and mechanisms of miR‐335‐5p in HNSCC. We showed a decreased expression of miR‐335‐5p in HNSCC samples from the TCGA and GEO databases. Consistently, we detected a downregulation of miR‐335‐5p in HNSCC cell lines and patient tissues. The expression of miR‐335‐5p was inversely correlated with advanced clinical TNM stage and lymph node metastasis in HNSCC patients. miR‐335‐5p overexpression inhibited HNSCC cell proliferation and induced apoptosis, while miR‐335‐5p inhibition had the opposite effects. miR‐335‐5p overexpression suppressed tumor growth in mice. Bioinformatic analyses and functional assays identified MAP3K2 as a target of miR‐335‐5p, and we showed that miR‐335‐5p downregulated mitogen‐activated protein kinase kinase kinase 2 (MAP3K2) expression in HNSCC cells. We found an inverse association between MAP3K2 and miR‐335‐5p expression in 38 pairs of HNSCC tissues. Furthermore, the effect of miR‐335‐5p overexpression on growth and metastasis as well as cell apoptosis in HNSCC cells could be partially rescued by MAP3K2 expression. Collectively, our data show that miR‐335‐5p inhibits the development of HNSCC by regulating MAP3K2 expression. Thus, these findings offer novel insights into a potential therapeutic strategy for HNSCC patients. [ABSTRACT FROM AUTHOR]