Predicting the Benefit of Adjuvant Aromatase Inhibitor Therapy in Postmenopausal Breast Cancer Patients with Phosphorylated S6K1 Expression Status / 한국유방암학회지

PURPOSE: Phosphorylated ribosomal S6 kinase 1 (pS6K1) is a major downstream regulator of the mammalian target of rapamycin (mTOR) pathway. Recent studies have addressed the role of S6K1 in adipogenesis. pS6K1 may affect the outcome of estrogen depletion therapy in patients with hormone-sensitive breast cancer due to its association with adipogenesis and increased local estrogen levels. This study aimed to investigate the potential of pS6K1 as a predictive marker of adjuvant aromatase inhibitor (AI) therapy outcome in postmenopausal or ovarian function-suppressed patients with hormone-sensitive breast cancer.METHODS: Medical records were retrospectively reviewed in postmenopausal or ovarian function-suppressed patients with estrogen receptor-positive and node-positive primary breast cancer. pS6K1 expression status was scored on a scale from 0 (negative) to 3+ (positive) based on immunohistochemical analysis.RESULTS: A total of 428 patients were eligible. The median follow-up duration was 44 months (range, 1–90). In patients with positive pS6K1 expression, AIs significantly improved disease-free survival (DFS) compared to selective estrogen receptor modulators (SERMs) (5 year-DFS: 83.5% vs. 50.7%, p = 0.016). However, there was no benefit of AIs on DFS in the pS6K1 negative group (5 year-DFS 87.6% vs. 91.4%, p = 0.630). On multivariate analysis, AI therapy remained a significant predictor for DFS in the pS6K1 positive group (hazard ratio, 0.39; 95% confidence interval, 0.16–0.96; p = 0.041). pS6K1 was more effective in predicting the benefit of AI therapy in patients with ages < 50 (p = 0.021) compared to those with ages ≥ 50 (p = 0.188).CONCLUSION: pS6K1 expression may predict AI therapy outcomes and serve as a potential predictive marker for adjuvant endocrine therapy in postmenopausal and ovarian function-suppressed patients with hormone-sensitive breast cancer. AIs may be more effective in patients with pS6K1 positive tumors, while SERM could be considered an alternative option for patients with pS6K1 negative tumors.

Inhibition of Mast Cell Function and Proliferation by mTOR Activator MHY1485

Mast cells integrate innate and adaptive immunity and are implicated in pathophysiological conditions, including allergy, asthma, and anaphylaxis. Cross-linking of the high-affinity IgE receptor (FcεRI) initiates diverse signal transduction pathways and induces release of proinflammatory mediators by mast cells. In this study, we demonstrated that hyperactivation of mechanistic target of rapamycin (mTOR) signaling using the mTOR activator MHY1485 suppresses FcεRI-mediated mast cell degranulation and cytokine secretion. MHY1485 treatment increased ribosomal protein S6 kinase (S6K) and eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1) phosphorylation, which are downstream targets of mTOR complex 1 (mTORC1), but decreased phosphorylation of Akt on mTOR complex 2 (mTORC2) target site serine 473. In addition, this activator decreased β-hexosaminidase, IL-6, and tumor necrosis factor α (TNF-α) release in murine bone marrow-derived mast cells (BMMCs) after FcεRI stimulation. Furthermore, MHY1485-treated BMMCs showed significantly decreased proliferation when cultured with IL-3. These findings suggested hyperactivation of mTORC1 as a therapeutic strategy for mast cell-related diseases.

Phosphorylated S6 Kinase-1 as Predictive Marker of Lapatinib Efficacy in Human Epidermal Growth Factor Receptor 2-Positive Metastatic Breast Cancer Patients

PURPOSE: The 40S ribosomal protein S6 kinase-1 (S6K1) is a crucial downstream effector of the PI3K/AKT/mTOR pathway. S6K1 overexpression is found in 10% to 30% of breast cancers and is associated with aggressive disease and poor prognosis. Herein, we investigated the relationship between the expression of phosphorylated S6K1 (p-S6K1) and efficacy of lapatinib in patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer. METHODS: We retrospectively analyzed the data of 36 patients with HER2-positive metastatic breast cancer treated with lapatinib between January 2010 and September 2014. The p-S6K1 expression status of the primary tumor was assessed via immunohistochemistry using a mouse monoclonal antibody. RESULTS: Fourteen of the 36 patients (38.9%) had p-S6K1-positive tumors. The median progression-free survival (PFS) of patients with p-S6K1-positive tumors was significantly longer than that of patients with p-S6K1-negative tumors (13.4 months vs. 7.1 months, p=0.025). In multivariate analysis, p-S6K1 positivity remained an independent, favorable predictive factor for PFS (hazard ratio, 0.32; 95% confidence interval, 0.11–0.97; p=0.044). CONCLUSION: The high expression of p-S6K1 was significantly associated with prolonged PFS, suggesting that p-S6K1 can be a potential biomarker for predicting the efficacy of lapatinib in patients with HER2-positive metastatic breast cancer.

Role of Triggering Receptor Expressed on Myeloid Cell-1 Expression in Mammalian Target of Rapamycin Modulation of CD8T-cell Differentiation during the Immune Response to Invasive Pulmonary Aspergillosis / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Triggering receptor expressed on myeloid cell-1 (TREM-1) may play a vital role in mammalian target of rapamycin (mTOR) modulation of CD8+ T-cell differentiation through the transcription factors T-box expressed in T-cells and eomesodermin during the immune response to invasive pulmonary aspergillosis (IPA). This study aimed to investigate whether the mTOR signaling pathway modulates the proliferation and differentiation of CD8+ T-cells during the immune response to IPA and the role TREM-1 plays in this process.</p><p><b>METHODS</b>Cyclophosphamide (CTX) was injected intraperitoneally, and Aspergillus fumigatus spore suspension was inoculated intranasally to establish the immunosuppressed IPA mouse model. After inoculation, rapamycin (2 mg.kg-1.d-1) or interleukin (IL)-12 (5 μg/kg every other day) was given for 7 days. The number of CD8+ effector memory T-cells (Tem), expression of interferon (IFN)-γ, mTOR, and ribosomal protein S6 kinase (S6K), and the levels of IL-6, IL-10, galactomannan (GM), and soluble TREM-1 (sTREM-1) were measured.</p><p><b>RESULTS</b>Viable A. fumigatus was cultured from the lung tissue of the inoculated mice. Histological examination indicated greater inflammation, hemorrhage, and lung tissue injury in both IPA and CTX + IPA mice groups. The expression of mTOR and S6K was significantly increased in the CTX + IPA + IL-12 group compared with the control, IPA (P = 0.01; P= 0.001), and CTX + IPA (P = 0.034; P= 0.032) groups, but significantly decreased in the CTX + IPA + RAPA group (P < 0.001). Compared with the CTX + IPA group, the proportion of Tem, expression of IFN-γ, and the level of sTREM-1 were significantly higher after IL-12 treatment (P = 0.024, P= 0.032, and P= 0.017, respectively), and the opposite results were observed when the mTOR pathway was blocked by rapamycin (P < 0.001). Compared with the CTX + IPA and CTX + IPA + RAPA groups, IL-12 treatment increased IL-6 and downregulated IL-10 as well as GM, which strengthened the immune response to the IPA infection.</p><p><b>CONCLUSIONS</b>mTOR modulates CD8+ T-cell differentiation during the immune response to IPA. TREM-1 may play a vital role in signal transduction between mTOR and the downstream immune response.</p>

The p90 ribosomal S6 kinase 2 specifically affects mitotic progression by regulating the basal level, distribution and stability of mitotic spindles

RSK2, also known as RPS6KA3 (ribosomal protein S6 kinase, 90 kDa, polypeptide 3), is a downstream kinase of the mitogen-activated protein kinase (MAPK) pathway, which is important in regulating survival, transcription, growth and proliferation. However, its biological role in mitotic progression is not well understood. In this study, we examined the potential involvement of RSK2 in the regulation of mitotic progression. Interestingly, depletion of RSK2, but not RSK1, caused the accumulation of mitotic cells. Time-lapse analysis revealed that mitotic duration, particularly the duration for metaphase-to-anaphase transition was prolonged in RSK2-depleted cells, suggesting activation of spindle assembly checkpoint (SAC). Indeed, more BubR1 (Bub1-related kinase) was present on metaphase plate kinetochores in RSK2-depleted cells, and depletion of BubR1 abolished the mitotic accumulation caused by RSK2 depletion, confirming BubR1-dependent SAC activation. Along with the shortening of inter-kinetochore distance, these data suggested that weakening of the tension across sister kinetochores by RSK2 depletion led to the activation of SAC. To test this, we analyzed the RSK2 effects on the stability of kinetochore–microtubule interactions, and found that RSK2-depleted cells formed less kinetochore–microtubule fibers. Moreover, RSK2 depletion resulted in the decrease of basal level of microtubule as well as an irregular distribution of mitotic spindles, which might lead to observed several mitotic progression defects such as increase in unaligned chromosomes, defects in chromosome congression and a decrease in pole-to-pole distance in these cells. Taken together, our data reveal that RSK2 affects mitotic progression by regulating the distribution, basal level and the stability of mitotic spindles.

The p90rsk-mediated signaling of ethanol-induced cell proliferation in HepG2 cell line

Ribosomal S6 kinase is a family of serine/threonine protein kinases involved in the regulation of cell viability. There are two subfamilies of ribosomal s6 kinase, (p90rsk, p70rsk). Especially, p90rsk is known to be an important downstream kinase of p44/42 MAPK. We investigated the role of p90rsk on ethanol-induced cell proliferation of HepG2 cells. HepG2 cells were treated with 10~50 mM of ethanol with or without ERK and p90rsk inhibitors. Cell viability was measured by MTT assay. The expression of pERK1, NHE1 was measured by Western blots. The phosphorylation of p90rsk was measured by ELISA kits. The expression of Bcl-2 was measured by qRT-PCR. When the cells were treated with 10~30 mM of ethanol for 24 hour, it showed significant increase in cell viability versus control group. Besides, 10~30 mM of ethanol induced increased expression of pERK1, p-p90rsk, NHE1 and Bcl-2. Moreover treatment of p90rsk inhibitor attenuated the ethanol-induced increase in cell viability and NHE1 and Bcl-2 expression. In summary, these results suggest that p90rsk, a downstream kinase of ERK, plays a stimulatory role on ethanol-induced hepatocellular carcinoma progression by activating anti-apoptotic factor Bcl-2 and NHE1 known to regulate cell survival.

Expression of PI3K pathway proteins in refractory epilepsy associated with cortical malformation development / 中华病理学杂志

<p><b>OBJECTIVE</b>To investigate the expression of TSC1, TSC2, p-mTOR, p-4E-BP1, p-p70S6K and p-S6 in refractory epilepsy associated malformation of cortical development (MCD) tissues.</p><p><b>METHODS</b>A total of 43 cases of refractory epilepsy were involved in the study, and all the patients were treated in Xuanwu Hospital during 2005 - 2008, including focal cortical dysplasia type IIa (11 cases) and type IIb (11 cases), tuberous sclerosis complex (10 cases) and ganalioglioma (11 cases), and other 12 cases were used as control. These cases were divided into 7 study groups and immunohistochemical EnVision method was used. To detect the location and intensity of TSC1, TSC2, p-mTOR, p-4E-BP1, p-p70S6K and p-S6 expression in every group. Then the Image-Pro Plus 6.0 image processing and analysis software were used to measure the number, area, integrating absorbance (IA) of positive cells in every samples. The statistical software SPSS 16.0 was used to analyze the data.</p><p><b>RESULTS</b>The immunolocalization of TSC1 and TSC2 was similar. It could be observed the expression of various levels in the cytoplasm of dysmorphic neurons, balloon cells, giant cells, ganglioglioma cells and normal neurons. TSC1 staining in normal neurons was more notably than others but TSC2 staining in giant cells was weaker than other samples. p-mTOR mainly presented in giant cells, which could also be observed in astrocyte. P-4E-BP1 presented in the cytoplasm and nuclear membrane of balloon cells, giant cells and ganglioglioma cells, the staining of giant cells was stronger than balloon cells, but their staining were weaker than ganglioglioma cells. P-p70S6K mainly expressed in giant cells and less commonly presented in balloon cells. P-S6 typically presented in all abnormal glioneuronal cells and it nearly did not present in the normal neurons of N-CTX group.</p><p><b>CONCLUSIONS</b>PI3K pathway, at least in part, involves in the occurrence of MCD, and may play an important role in the pathogenesis.</p>

The Clinicopathological Factors That Determine a Local Recurrence of Rectal Cancers That Have Been Treated with Surgery and Chemoradiotherapy / 대한방사선종양학회지

PURPOSE: To evaluate the pathological prognostic factors related to local recurrence after radical surgery and adjuvant radiation therapy in advanced rectal cancer. MATERIALS AND METHODS: Fifty-four patients with advanced rectal cancer who were treated with radical surgery followed by adjuvant radiotherapy and chemotherapy between February 1993 and December 2001 were enrolled in this study. Among these patients, 14 patients experienced local recurrence. Tissue specimens of the patients were obtained to determine pathologic parameters such as histological grade, depth of invasion, venous invasion, lymphatic invasion, neural invasion and immunohistopathological analysis for expression of p53, Ki-67, c-erb, ezrin, c-met, phosphorylated S6 kinase, S100A4, and HIF-1 alpha. The correlation of these parameters with the tumor response to radiotherapy was statistically analyzed using the chi-square test, multivariate analysis, and the hierarchical clustering method. RESULTS: In univariate analysis, the histological tumor grade, venous invasion, invasion depth of the tumor and the over expression of c-met and HIF-1 alpha were accompanied with radioresistance that was found to be statistically significant. In multivariate analysis, venous invasion, invasion depth of tumor and over expression of c-met were also accompanied with radioresistance that was found to be statistically significant. By analysis with hierarchical clustering, the invasion depth of the tumor, and the over expression of c-met and HIF-1 alpha were factors found to be related to local recurrence. Whereas 71.4% of patients with local recurrence had 2 or more these factors, only 27.5% of patients without local recurrence had 2 or more of these factors. CONCLUSION: In advanced rectal cancer patients treated by radical surgery and adjuvant chemo-radiation therapy, the poor prognostic factors found to be related to local recurrence were HIF-1 alpha positive, c-met positive, and an invasion depth more than 5.5 mm. A prospective study is necessary to confirm whether these factors would be useful clinical parameters to measure and predict a radio-resistance group of patients.

The S6 kinase signaling pathway in the control of development and growth

The discussion will focus on the role of the ribosomal protein S6 kinase (S6K) signaling pathway in the regulation of cell growth and proliferation. Although 40S ribosomal protein S6 phosphorylation was first described 25 years ago (Gressner and Wool, 1974), it only recently has been implicated in the translational up-regulation of mRNAs coding for the components of protein synthetic apparatus (Fumagalli and Thomas, 2000). These mRNAs contain an oligopyrimidine tract at their 5' transcriptional start site, termed a 5'TOP, which has been shown to be essential for their regulation at the translational level (Meyuhas et al., 1996). In parallel, a great deal of information has accumulated concerning the identification of the signaling pathway and the regulatory phosphorylation sites involved in controlling S6K activation (Dufner and Thomas, 1999). Despite this knowledge we are only beginning to identify the direct upstream elements involved in growth factor-induced kinase activation (Dennis et al., 2001; Pullen et al., 1998). Use of the immunosuppressant rapamycin, a bacterial macrolide, in conjunction with dominant interfering and activated forms of S6K1 has helped to establish the role of this signaling cascade in the regulation of growth and proliferation (Dennis and Thomas, 2002). In addition, current studies employing the mouse as well as Drosophila melanogaster have provided new insights into physiological function of S6K in the animal (Montagne et al., 1999; Pende et al., 2000). Loss of dS6K function in Drosophila melanogaster demonstrated its paramount importance in development and growth control (Montagne et al., 1999), whereas deletion of the S6K1 gene in the mouse led to an animal of reduced size and the identification of the S6K1 homologue, S6K2 (Shima et al., 1998). Such mice are significantly smaller during fetal development (Shima et al., 1998) and hypoinsulinemic in the adult, conditions known to lead to type 2 diabetes (Pende et al., 2000)