## 3 miRNAs and Molecular Chaperones in Brain Tumors
### Molecular Chaperones in Brain Tumors  
Molecular chaperones are the main components of the chaperoning (chaperone) system (CS) of an organism, which is also constituted of co-chaperones, chaperone cofactors and chaperone receptors and interactors, forming different functional networks [183; 184]. Some chaperones are called Hsp (from heat shock protein), since they increase in response to heat shock and other stressors [185; 186; 187; 188]. Although not all chaperones are Hsps and vice versa not all Hsps are chaperones, both terms have been  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Tumor**} & \multirow{2}{*}{**miRNA**} & \multirow{2}{*}{**Function**} & \multicolumn{3}{c}{**Quantity**} & \multirow{2}{*}{**Ref. **} \\ \cline{3-3} \cline{5-6}  & & & **Level** & & **Tissue/Cell** & \\ \hline \multirow{8}{*}{**Glioma**} & miR-335 & OncomiR & Increased & GBM cells and derived EVs & [168] \\  & miR-451 & OncomiR & Increased & GBM cells and derived EVs & [178] \\  & miR-1238 & OncomiR & Low levels in cells & GBM cells and derived EVs & [179] \\  & miR-1 & Tumor suppressor & Released in EVs & GBM cells derived EVs & [180] \\  & miR-151a & Tumor suppressor & Low levels & Blood; GBM specimens & [139; 146; 149] \\  & miR-185 & Tumor suppressor & Decreased & GBM cell lines and blood & [151; 152] \\  & miR-203 & Tumor suppressor & Low levels & Blood & [147; 148] \\  & miR-205 & Tumor suppressor & Low levels & GBM tissues and cell lines & [181; 182] \\  & miR-454 & Tumor suppressor & Low levels & GBM tissues and cell lines & [153] \\  & miR-605 & Tumor suppressor & Increased & Meaning biomass tissues & [199] \\ \hline \multirow{8}{*}{**Meningioma**} & miR-224 & OncomiR & Increased & Meningioma tissues; & [157] \\  & miR-335 & OncomiR & Low levels & Meningioma cell & \\  & miR-145 & Tumor suppressor & Low levels & Benign meningioma tissue & [154; 155] \\  & miR-200a & Tumor suppressor & High levels & Blood & [160] \\  & miR-106a-5p, miR-219-5p, Diagnostic and prognostic & Lymph levels & Blood & [160] \\  & miR-375, and miR-409-3p & Biomarkers & Increased & Blood & [161] \\  & miR-197 and miR-224 & Diagnostic and prognostic & Increased & & \\  & miR-15a-5p, miR-146a-5p, and miR-331-3p & & & & [161] \\  & & & & & \\  & & & & & \\  & & & & & \\  & & & & & \\  & & & & & \\  & &  
used indistinctly for years, as if they were true synonyms. This unfortunate confusion is practically impossible to eradicate from the literature and continues to thrive. Therefore, we use the terms chaperone and Hsp interchangeably in this work. The canonical functions of chaperones pertain to protein homeostasis and quality control [189; 190; 191; 192; 193; 194; 195; 196; 197; 198]. However, chaperones have also noncanonical functions unrelated to the maintenance of protein homeostasis, including participation in immune and inflammatory reactions [199; 190; 191; 192; 193; 194; 195; 196; 197; 198; 199; 200; 201]. The CS interacts with the immune system and when malfunctional, it becomes a pathogenic factor in autoimmune and inflammatory diseases. The diseases in which components of the chaperone system play an etiological-pathogenic role are the chaperopathies [202]. As for most diseases, chaperopathies can be genetic or acquired, with the former being the result of a gene variant, e.g., mutation, while the acquired chaperopathies are characterized by structural and functional abnormalities in the chaperone protein, but its gene is normal. In addition, chaperopathies can be classified according to its main feature as by defect, by excess, and by mistake [203]. Typically, chaperopathies associated with cancer are by mistake, namely the pathogenic chaperone helps the tumor cell rather than defend the human host against it. Since chaperones are classically considered cytoprotective and guardians of protein homeostasis, their helping malignant cells to grow, proliferate, and disseminate appear as mistaken activities, so to speak.