Functions And Mechanisms Of LncRNAs In Tumor Microenvironmental Response And Metabolic Reprogramming

Cancer cells require metabolic reprogramming and microenvironment remodeling to adapt to environmental stresses and support deregulated tumorous progression.Intracellular calcium flux and calcium signals play an important regulatory role in tumor development.However,the underlying mechanism is awaiting further investigation.Applying genetic screening by si RNA library,we identified a tumor growth and metabolism-associated long non-coding RNA（lnc RNA）numbered NR₀38131.We renamed it as lnc RNA for Calcium-dependent Kinase Activation,CamK-A.Results of clinical cohort analysis showed that CamK-A was upregulated in multiple human tumor tissues,suggesting the oncogenic function of CamK-A.Through biochemical approaches,we revealed that CamK-A could activate the calciumdependent calmodulin kinase PNCK（also known as Ca MKIβ）,and facilitated the downstream recruitment of IκBα,mediating the phosphorylation of serine 32 of IκBα and subsequent degradation of IκBα.This process activates the calcium-dependent NF-κB pathway,and activates the transcription of various target genes such as GLUT3,IL-6,IL-8,and VEGF.This regulatory mechanism leads to tumorous metabolic reprogramming and microenvironment remodeling,including recruitment of macrophages and angiogenesis.As tumors grow,cancer cells within solid tumors are generally stressed by hypoxia environment.We found that hypoxia could boost intracellular calcium and thereby trigger PNCK-CamK-A-IκBα axis activation continuously,which helps tumor cells respond to environmental stress and promotes the process of tumor microenvironment remodeling.In addition,applying xenograft assays and analyzing tumor samples of clinical cohorts,we found that CamK-A expression was positively synergistic with the activation of PNCK-NF-κB signal axis,which further emphasizes the physiological significance of CamK-A in tumor progression.Knockdown of CamK-A can significantly inhibit tumor growth and weaken tumor microenvironment in vivo,emphasizing the physiological significance of CamK-A in tumor progression.In conclusion,our study revealed the regulatory role of Camk-A in tumor microenvironmental hypoxic stress-induced Ca2+ signaling,and concertedly promoting tumor metabolic reprogramming and microenvironmental remodeling.The investigation of CamK-A provides a new potential approach for overcoming tumor metabolism and microenvironmental barriers.Organelles entail specialized biomolecules to define their essential functions,which is critical for cellular homeostasis.Long non-coding RNAs（lnc RNAs）are revealed to function in multiple biological processes.However,systematically elucidating the subcellular distribution and function of biomolecules such as lnc RNAs in cellular homeostasis and diseases has not been fully achieved.Here,we optimized the immunoprecipitation-based subcellular fraction method,and revealed diverse and abundant organelle-associated lnc RNAs in mitochondria,lysosomes and endoplasmic reticulum.Among them,we dissected the dynamic distribution and local function of mitochondrial lnc RNA GAS5 during nutrient stress.Glucose starvation induces mitochondrial import of GAS5 to transfer metabolic stress signal,and promotes its binding to mitochondrial malate dehydrogenase（MDH2）.Mitochondrial GAS5 mediates deacetylation of MDH2 and disassociation the metabolon of fumarate hydratase,MDH2 and citrate synthase,leading to suppression of mitochondrial TCA cycling and energy-stress-induced cell growth arrest.GAS5 negatively correlates with expression level of MDH2,and benefits overall survival in breast cancer cohort.Together,our investigation of organellar lnc RNAs presents their properties and biological significance in cell metabolism and energy homeostasis regulation,highlighting the potential of subcellular lnc RNAs in treating metabolic disorders and related diseases.