P-mTOR Expression and Implication in Breast Carcinoma: A Systematic Review and Meta-Analysis

Rapamycin improves the survival of epilepsy model cells by blocking phosphorylation of mTOR base on computer simulations and cellular experiments

PURPOSE

Epilepsy is a chronic brain dysfunction characterized by recurrent epileptic seizures. Rapamycin is a naturally occurring macrolide from Streptomyces hygroscopicus, and rapamycin may provide a protective effect on the nervous system by affecting mTOR. Therefore, we investigated the pharmacologic mechanism of rapamycin treating epilepsy through bioinformatics analysis, cellular experiments and supercomputer simulation.

METHODS

Bioinformatics analysis was used to analyze targets of rapamycin treating epilepsy. We established epilepsy cell model by HT22 cells. RT-qPCR, WB and IF were used to verify the effects of rapamycin on mTOR at gene level and protein level. Computer simulations were used to model and evaluate the stability of rapamycin binding to mTOR protein.

RESULTS

Bioinformatics indicated mTOR played an essential role in signaling pathways of cell growth and cell metabolism. Cellular experiments showed that rapamycin could promote cell survival, and rapamycin did not have an effect on mRNA expression of mTOR. However, rapamycin was able to significantly inhibit the phosphorylation of mTOR at protein level. Computer simulations indicated that rapamycin was involved in the treatment of epilepsy through regulating phosphorylation of mTOR at protein level.

CONCLUSION

We found that rapamycin was capable of promoting the survival of epilepsy cells by inhibiting the phosphorylation of mTOR at protein level, and rapamycin did not have an effect on mRNA expression of mTOR. In addition to the traditional study that rapamycin affects mTORC1 complex by acting on FKBP12, this study found rapamycin could also directly block the phosphorylation of mTOR, therefore affecting the assembly of mTORC1 complex and mTOR signaling pathway.

The clinicopathological and prognostic significance of mTOR and p-mTOR expression in patients with non-small cell lung cancer: A meta-analysis

BACKGROUND

The mammalian target of rapamycin (mTOR) has a crucial role in carcinogenesis, angiogenesis, cellular proliferation, and metastasis; however, its significance in non-small cell lung cancer (NSCLC) remains contentious. Consequently, this study aims to assess the clinicopathological and prognostic importance of mTOR/p-mTOR expression in NSCLC.

METHODS

Literature retrieval was undertaken by searching English databases PubMed, EMBASE, Web of Science, and Cochrane Library as well as Chinese databases CNKI, Wan Fang, and VIP for full-text publications that satisfied our eligibility criteria up to November 2021. STATA 12.0 was used to conduct statistical analysis (STATA Corporation, College Station, TX).

RESULTS

This meta-analysis includes a total of 4683 patients from 28 primary publications. mTOR/p-mTOR expression was associated with sex (OR = 0.608, 95% CI: 0.442-0.836), lymph node metastasis (OR = 2.084, 95% CI: 1.437-3.182), and CEA (OR = 1.584, 95% CI: 1.135-2.209), but not with age, histological type, depth of tumor invasion, distant metastasis, TNM stage, differentiation degree, tumor size, or smoking. In addition, the expression of mTOR/p-mTOR is related to shorter overall survival in NSCLC patients (HR = 1.415, 95% CI: 1.051-1.905).

CONCLUSION

Positive mTOR/p-mTOR expression was substantially correlated with unfavorable conditions on the sex, lymph node metastases, and CEA levels. mTOR/p-mTOR may indicate a bad prognosis for NSCLC. The current findings must be confirmed and changed by other high-quality research employing a multivariate analysis on bigger sample size.

mTOR Repression in Response to Amino Acid Starvation Promotes ECM Degradation Through MT1-MMP Endocytosis Arrest

Under conditions of starvation, normal and tumor epithelial cells can rewire their metabolism toward the consumption of extracellular proteins, including extracellular matrix-derived components as nutrient sources. The mechanism of pericellular matrix degradation by starved cells has been largely overlooked. Here it is shown that matrix degradation by breast and pancreatic tumor cells and patient-derived xenograft explants increases by one order of magnitude upon amino acid and growth factor deprivation. In addition, it is found that collagenolysis requires the invadopodia components, TKS5, and the transmembrane metalloproteinase, MT1-MMP, which are key to the tumor invasion program. Increased collagenolysis is controlled by mTOR repression upon nutrient depletion or pharmacological inhibition by rapamycin. The results reveal that starvation hampers clathrin-mediated endocytosis, resulting in MT1-MMP accumulation in arrested clathrin-coated pits. The study uncovers a new mechanism whereby mTOR repression in starved cells leads to the repurposing of abundant plasma membrane clathrin-coated pits into robust ECM-degradative assemblies.

Histological and Immunohistochemical Evaluation of Phosphorylated Mechanistic Target of Rapamycin in Canine Skin Tumours

The mechanistic target of rapamycin (mTOR) plays an important role in cellular functions, including growth and metabolism. Recently, mTOR and the activated phosphorylated form of mTOR (p-mTOR) have been reported as potential prognostic markers in many human tumours. However, there are few studies on its activation in canine tumours. We investigated the expression of p-mTOR in 17 canine skin tumours (CSTs), of which 58.8% were epithelial and melanocytic and 41.2% were mesenchymal tumours. Seventy-six per cent of the CSTs had high or moderate expression of p-mTOR. Mean p-mTOR expression in the epithelial and melanocytic tumours (5.7 ± 0.56) was significantly higher (P <0.05) than that of the mesenchymal tumours (3.14 ± 0.55). The age of the animals had no influence on p-mTOR expression. These findings suggest that activation of m-TOR is important in the development of skin tumours in dogs and the study might form the basis for further research on utilizing m-TOR inhibitors as improved therapeutic modalities in canine skin tumours.

Assessment of the expression pattern of mTOR-associated lncRNAs and their genomic variants in the patients with breast cancer

The mechanistic target of rapamycin (mTOR) is a fundamental component of a signaling pathway that is involved in the pathogenesis of breast cancer via different mechanisms. This pathway is functionally linked with a number of small nucleolar RNA host genes (SNHGs). In the present project, we have searched for the expression quantitative trait loci (eQTLs) within SNHGs that are possibly involved in the pathogenesis of breast cancer. Following this in silico step, we have assessed expression levels of mTOR and four SNHGs in malignant and nonmalignant samples obtained from 80 patients with breast cancer. We also genotyped rs4615861 of SNHG3 and rs3087978 of SNHG5 in the peripheral blood of patients. SNHG12 expression was not detected in any of the assessed malignant or nonmalignant tissues. So this gene was excluded from further steps. Expression of mTOR and other three long noncoding RNAs (lncRNAs) were significantly increased in the malignant tissues compared with the nonmalignant tissues. When classifying patients into down-/upregulation categorized based on the transcript levels of each gene in malignant tissue versus nonmalignant tissues, we noticed associations between expression of SNHG1 and stage (p = 0.03), expression of SNHG5 and grade (p = 0.05), as well as between expression of SNHG3 and history of oral contraceptive use (p = 0.04). We also detected higher levels of SNHG3 expression in estrogen receptor/progesterone receptor (ER/PR) negative tumors compared with the ER/PR positive tumors (p  = 0.003 and p = 0.01, respectively). Moreover, there was a trend toward higher expression of this lncRNA in HER2-positive tumors compared with the HER2-negative ones (p = 0.07). Combination of transcript levels of all genes could differentiate malignant tissues from nonmalignant tissues with the diagnostic power of 69% (p = 0.0001). The rs3087978 was associated with the expression of mTOR in malignant tissues in a way that TT and TG genotypes were associated with the higher and lower levels of expressions, respectively (p = 0.01). The current study underscores the significance of SNHGs in the pathogenesis of breast cancer.

Limited utility of tissue micro-arrays in detecting intra-tumoral heterogeneity in stem cell characteristics and tumor progression markers in breast cancer

Background

Intra-tumoral heterogeneity has been recently addressed in different types of cancer, including breast cancer. A concept describing the origin of intra-tumoral heterogeneity is the cancer stem-cell hypothesis, proposing the existence of cancer stem cells that can self-renew limitlessly and therefore lead to tumor progression. Clonal evolution in accumulated single cell genomic alterations is a further possible explanation in carcinogenesis. In this study, we addressed the question whether intra-tumoral heterogeneity can be reliably detected in tissue-micro-arrays in breast cancer by comparing expression levels of conventional predictive/prognostic tumor markers, tumor progression markers and stem cell markers between central and peripheral tumor areas.

Methods

We analyzed immunohistochemical expression and/or gene amplification status of conventional prognostic tumor markers (ER, PR, HER2, CK5/6), tumor progression markers (PTEN, PIK3CA, p53, Ki-67) and stem cell markers (mTOR, SOX2, SOX9, SOX10, SLUG, CD44, CD24, TWIST) in 372 tissue-micro-array samples from 72 breast cancer patients. Expression levels were compared between central and peripheral tumor tissue areas and were correlated to histopathological grading. 15 selected cases additionally underwent RNA sequencing for transcriptome analysis.

Results

No significant difference in any of the analyzed between central and peripheral tumor areas was seen with any of the analyzed methods/or results that showed difference. Except mTOR, PIK3CA and SOX9 (nuclear) protein expression, all markers correlated significantly (p < 0.05) with histopathological grading both in central and peripheral areas.

Conclusion

Our results suggest that intra-tumoral heterogeneity of stem-cell and tumor-progression markers cannot be reliably addressed in tissue-micro-array samples in breast cancer. However, most markers correlated strongly with histopathological grading confirming prognostic information as expression profiles were independent on the site of the biopsy was taken.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1495-6) contains supplementary material, which is available to authorized users.