p-mTOR expression is associated with better prognosis in luminal breast carcinoma

Low-Level Expression of p-S6 Is Associated with Nodal Metastasis in Patients with Head and Neck Cutaneous Squamous Cell Carcinoma

Cutaneous squamous cell carcinoma (cSCC) is the second most common form of skin cancer. The incidence of metastasis for cSCC is estimated to be around 1.2-5%. Ribosomal protein S6 (p-S6) and the p21 protein (p21) are two proteins that play central roles in other cancers. These proteins may be equally important in cSCC, and together, these could constitute a good candidate for metastasis risk assessment of these patients. We investigate the relationship of p-S6 and p21 expression with the impact on the prognosis of head and neck cSCC (cSCCHN). p-S6 and p21 expression was analyzed by immunohistochemistry on paraffin-embedded tissue samples from 116 patients with cSCCHN and associations sought with clinical characteristics. Kaplan-Meier estimators and Cox proportional hazard regression models were also used. The expression of p-S6 was significantly inversely associated with tumor thickness, tumor size, desmoplastic growth, pathological stage, perineural invasion and tumor buds. p21 expression was significantly inversely correlated with >6 mm tumor thickness, desmoplastic growth, and perineural invasion. p-S6-negative expression significantly predicted an increased risk of nodal metastasis (HR = 2.63, 95% CI 1.51-4.54; p < 0.001). p21 expression was not found to be a significant risk factor for nodal metastasis. These findings demonstrate that p-S6-negative expression is an independent predictor of nodal metastasis. The immunohistochemical expression of p-S6 might aid in better risk stratification and management of patients with cSCCHN.

Expression of mTOR in normal and pathological conditions

The mechanistic/mammalian target of rapamycin (mTOR), a protein discovered in 1991, integrates a complex pathway with a key role in maintaining cellular homeostasis. By comprising two functionally distinct complexes, mTOR complex 1 (mTORC1) and mTORC2, it is a central cellular hub that integrates intra- and extracellular signals of energy, nutrient, and hormone availability, modulating the molecular responses to acquire a homeostatic state through the regulation of anabolic and catabolic processes. Accordingly, dysregulation of mTOR pathway has been implicated in a variety of human diseases. While major advances have been made regarding the regulators and effectors of mTOR signaling pathway, insights into the regulation of mTOR gene expression are beginning to emerge. Here, we present the current available data regarding the mTOR expression regulation at the level of transcription, translation and mRNA stability and systematize the current knowledge about the fluctuations of mTOR expression observed in several diseases, both cancerous and non-cancerous. In addition, we discuss whether mTOR expression changes can be used as a biomarker for diagnosis, disease progression, prognosis and/or response to therapeutics. We believe that our study will contribute for the implementation of new disease biomarkers based on mTOR as it gives an exhaustive perspective about the regulation of mTOR gene expression in both normal and pathological conditions.

Body fatness and mTOR pathway activation of breast cancer in the Women's Circle of Health Study

Energy imbalance has an important role in breast cancer prognosis. Hyperactive mechanistic Target of Rapamycin (mTOR) pathway is associated with breast tumor growth, but the extent to which body fatness is associated with mTOR pathway activities in breast cancer is unclear. We performed immunostaining for mTOR, phosphorylated (p)-mTOR, p-AKT, and p-p70S6K in tumor tissue from 590 women (464 African Americans/Blacks and 126 Whites) with newly diagnosed invasive breast cancer in the Women's Circle of Health Study. Anthropometric measures were taken by study staff, and body composition was measured by bioelectrical impedance analysis. Linear regressions were used to estimate percent differences in protein expression between categories of body mass index (BMI), waist circumference, waist/hip ratio, fat mass, fat mass index, and percent body fat. We observed that BMI ≥ 35.0 vs. <25 kg/m2 was associated with 108.3% (95% CI = 16.9%-270.9%) and 101.8% (95% CI = 17.0%-248.8%) higher expression in p-mTOR and normalized p-mTOR, i.e., p-mTOR/mTOR, respectively. Quartiles 4 vs. 1 of waist/hip ratio was associated with 41.8% (95% CI = 5.81%-89.9%) higher mTOR expression. Similar associations were observed for the body fat measurements, particularly in patients with estrogen receptor-negative (ER-) tumors, but not in those with ER+ tumors, although the differences in associations were not significant. This tumor-based study found positive associations between body fatness and mTOR pathway activation, evident by a p-mTOR expression, in breast cancer. Our findings suggest that mTOR inhibition can be a treatment strategy to prevent the recurrence of these tumors in obese individuals.

Impact of PI3K/AKT/mTOR pathway activation on the prognosis of patients with head and neck squamous cell carcinomas

The PI3K/AKT/mTOR signaling pathway has emerged as one of the most frequently deregulated in head and neck squamous cell carcinomas (HNSCC). Numerous alterations of various upstream and downstream components have been described; however, their prognostic significance and impact on HNSCC patient survival remains to be established. This was addressed using an unbiased cohort of 93 consecutive and homogeneous surgically treated HNSCC patients and results confirmed in 432 HNSCC patients. Our findings reveal the high prevalence of S6 phosphorylation, a surrogate marker of mTORC1 activation, in HNSCC specimens (>70%) and, more importantly, demonstrate its relevance on clinical outcome. Phosphorylation of ribosomal protein S6 on either Ser235/236 or Ser240/244 was consistently and significantly correlated with favorable prognosis, although with differences depending on the tumor site. Thus, p-S6 expression was significantly correlated with better disease-specific survival specifically in the subgroup of laryngeal carcinoma patients (P< 0.001). In addition, multivariate regression models revealed p-S6 to be an inverse and independent predictor of lymph-node metastasis (P= 0.004) and distant metastasis (P= 0.006). Taken together, this study unveils an unprecedented correlation of mTOR activation with improved clinical outcome in patients with laryngeal carcinomas and uncovers the potential of p-S6 expression as a good prognostic biomarker and an inverse predictor of lymph node and distant metastases. These results should be of broad interest as immunohistochemical detection of p-S6 may help to stratify patients and guide treatment decisions.

Phosphorylated ribosomal protein S6 correlation with p21 expression and inverse association with tumor size in oral squamous cell carcinoma

BACKGROUND

The purpose of this study was to investigate the clinical relevance of phosphorylated ribosomal protein S6 (p-S6), a surrogate marker of mammalian target of rapamycin (mTOR) activation, and p21 in a series of 125 patients with oral squamous cell carcinomas (OSCCs).

METHODS

Immunohistochemical analysis was performed to ascertain the phosphorylation status of p-S6 at Ser235/236 and Ser240/244, p21, and p53 protein expression.

RESULTS

Expression of phosphorylated S6 protein on either serine 235/236 or serine 240/244 was detected in 83% and 88% tumors, respectively, and both of them were inversely and significantly correlated with the tumor size and local infiltration. Positive p21 expression was found in 91.5% of the cases, and was inversely correlated with tumor size. In OSCC, p21 expression correlates with p-S6 levels, a surrogate marker of mTOR activation, independently of p53 status.

CONCLUSION

Expression of both p21 and p-S6 was found to inversely associate with tumor size but not survival outcomes in patients with OSCC.

PI3K/AKT/mTOR pathway promotes progestin resistance in endometrial cancer cells by inhibition of autophagy

Endometrial cancer (EC) is now one of the most common malignant tumors in young women. In all, 90% of young patients with EC have a high expression of progesterone recep tor, can be treated with progestin, and have very good prognosis. However, some of the young EC patients are resistant to progestin, the mechanism of which is unclear. To illuminate the mechanism by which endometrial cells acquire progestin resistance, we treated Ishikawa cells by slowly increasing dosage of progestin and established a progestin-resistant cell subline. We show here that progesterone resistant cells acquire increased proliferation rate and interestingly decreased autophagy. To uncover the mechanism by which cells increase proliferation and bypass autophagy, we found higher activation of phosphatidylinositol 3-kinase/AKT/mTOR signaling pathway was necessary to this malignant acquirement by RNAi technique. Further, we elucidated that activation of mTOR was sufficient and necessary for progestin resistance. RAD001, an inhibitor of mTOR, decreased phosphorylation of mTOR and inhibited proliferation of progestin-resistant cancer cells by promoting autophagy. Thus, our results indicated that mTOR can be a target to treat the progestin-resistant EC.

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

Objective

Phosphorylated mammalian target of rapamycin (p-mTOR) is a promising prognostic marker in many types of cancer. However, its survival benefit in patients with breast carcinoma remains unknown. The aim of the present study was to assess the relationship between p-mTOR expression and prognosis in breast carcinoma based on a systematic review and meta-analysis.

Materials and Methods

Electronic databases (including Pubmed, Embase, ISI web of science, and Cochrane Library) were searched up to November 24, 2015. The outcome measures were hazard ratios (HRs) with 95% confidence interval (CI) for the association between the prognosis of breast carcinoma patients and p-mTOR expression. Primary end points were disease-free survival (DFS), overall survival (OS), and recurrence-free survival (RFS). Statistical analysis was performed with STATA 12.0.

Results

Nine cohort studies including 3051 patients met full eligibility criteria. The pooled HRs (95% CI) for OS, DFS, and RFS were 0.84 (0.27–2.63), 0.71 (0.40–1.23), and 0.48 (0.20–1.18), respectively.

Conclusions

Our findings suggested that p-mTOR overexpression was not significantly related to prognosis in breast carcinoma regarding OS and disease recurrence. Prospective studies are warranted to examine the association between p-mTOR expression and survival outcomes in breast carcinoma.

Stabilization of p21 by mTORC1/4E-BP1 predicts clinical outcome of head and neck cancers

The levels, regulation and prognostic value of p21 in head and neck squamous cell carcinomas (HNSCC) has been puzzling for years. Here, we report a new mechanism of regulation of p21 by the mTORC1/4E-BP1 pathway. We find that non-phosphorylated 4E-BP1 interacts with p21 and induces its degradation. Accordingly, hyper-activation of mTORC1 results in phosphorylation of 4E-BP1 and stabilization of p21. In HNSCC, p21 levels strongly correlate with mTORC1 activity but not with p53 status. Finally, clinical data indicate that HNSCC patients with p21 and phospho-S6-double-positive tumours present a better disease-specific survival. We conclude that over-activation of the mTORC1/4E-BP1/p21 pathway is a frequent and clinically relevant alteration in HNSCC.

The molecular pathways involving p21 and mTORC1 are frequently deregulated in head and neck squamous cell carcinomas (HNSCC). Here, Llanos et al. report a mechanism that regulates p21 stability through the mTORC1/4E-BP1 pathway independently of p53, and show that the mechanism is prevalent in HNSCC.

The mammalian target of rapamycin complex 1 (mTORC1) in breast cancer: the impact of oestrogen receptor and HER2 pathways

The mammalian target of rapamycin complex 1 (mTORC1) is a downstream of the PI3K/Akt pathway which affects cancer development. mTORC1 has many downstream signalling effectors that can enhance different cellular responses. This study aims to investigate the expression of mTORC1 in breast cancer (BC) and correlate it with key clinicopathological and molecular features of BC especially to proteins related to oestrogen receptor (ER) and HER2 pathways in different BC classes. Moreover, mTORC1 expression was assessed in 6 BC cell lines including ER+ and ER- cell lines with and without HER2 transfection. Immunohistochemistry was used to assess the expression of phospho (p) mTORC1 in a large (n = 1300) annotated BC series prepared as tissue microarray. Reverse phase protein array (RPPA) was used to assess its expression in the different BC cell lines. The expression of p-mTORC1 was cytoplasmic with moderate/high expression noted in 44 % of BC. p-mTORC1 expression was associated with clinicopathological variables characteristic of good prognosis. Positive correlation with ER, ER-related proteins AKT, PI3K and luminal differentiation markers were observed in the whole series and in the ER+HER2- subgroup. Association with HER2 was mainly observed in the ER-negative class. RPPA indicated that p-mTORC1 expression was mainly related to ER expression and with better outcome in the Akt positive tumours. p-mTORC1 is associated with good prognostic features. Its expression is related to ER and ER related proteins in addition to AKT and PI3K. Its relation with HER2 expression is mainly seen in the absence of ER expression.