Serotonin acts through YAP to promote cell proliferation: mechanism and implication in colorectal cancer progression.

Serotonin, also known as 5-hydroxytryptamine (5-HT), is a key messenger that mediates several central and peripheral functions in the human body. Emerging evidence indicates that serotonin is critical in tumorigenesis, but its role in colorectal cancer remains elusive. Herein, we report that serotonin transporter (SERT) transports serotonin into colorectal cancer cells, enhancing Yes-associated protein (YAP) expression and promoting in vitro and in vivo colon cancer cell growth. Once within the cells, transglutaminase 2 (TG2) mediates RhoA serotonylated and activates RhoA-ROCK1/2 signalling to upregulate YAP expression in SW480 and SW1116 cells. Blocking SERT with citalopram reversed the serotonin-induced YAP expression and cell proliferation, inhibiting serotonin's effects on tumour formation in mice. Moreover, SERT expression was correlated with YAP in pathological human colorectal cancer samples and the levels of 5-HT were highly significant in the serum of patients with colorectal cancer. Together, our findings suggested that serotonin enters cells via SERT to activate RhoA/ROCK/YAP signalling to promote colon cancer carcinogenesis. Consequently, targeting serotonin-SERT-YAP axis may be a potential therapeutic strategy for colorectal cancer. Video abstract.

[Preparation of cytoplasts from HL-60 cells].

This experimental research was aimed to establish an optimum system of enucleation, purification and identification for preparing the cytoplasts of suspension culture cells in order to undertake cell recombination. Human leukemia HL-60 cells in suspension culture were purified by 42% Percoll density gradient centrifugation and low-speed centrifugation at 1 500r/min, respectively. The purified HL-60 cells were treated with cytochalasin B (CB) alone or combined with colcchicine and enucleated by isopycnic gradient centrifugation on 50% Percoll at 25 degrees C and 34 degrees C, respectively. Cytoplasts made from HL-60 cells were purified through gradient centrifugation by 37%, 38% and 40% Percoll, respectively. The final cytoplasts were identified by Wright-Giemsa staining and 4,6-diamidino-2-phenylidole dihydrochloride (DAPI)/5, 6-carboxyflu-orescein diacetate succinimidyl ester (CFSE) double-staining. The phenotype and mitochondrial membrane potential of HL-60 cytoplasts were analyzed by flow cytometry. The results indicated that the enucleation ratio of HL-60 cells induced by CB combined with colcchicine was up to 91. 98% +/-4. 29%, which was significantly higher than that in CB alone group (74. 95% +/- 3. 02%)(P<0. 01). The rates of enucleation and cytoplast with diameter over 5min in 34 degrees C group were higher than those in 25 degrees C group (all P<0. 01). The cytoplast purities were (95.43 +/- 0. 59)% in 38% Percoll groups,which were higher than those of 40% Percoll (P<0. 05). Nucleus and caryoplasm could be clearly distinguished by DAPI and CFSE double labeling. The results further showed that the phenotype of HL-60 cytoplasts had no significant change, and the activity of the cytoplasts was above 80% within 12h. It is concluded that enucleation throuth density gradient centrifugation on 50% Percoll mediated by CB combined with colcchicine, 38%Percoll of purification followed by DAPI/CFSE double labeling and MMP detection is an optimum scheme for preparation and identification of cytoplast from suspension culture cells.

Biological role of long non-coding RNA FTX in cancer progression.

Long non-coding RNAs (LncRNAs) are involved in several types of cancer and participate actively in tumorigenesis and disease progression. LncRNA FTX is the transcription product of the FTX gene located at the X-inactivation center (Xic). LncRNA FTX has been shown to regulate cancer cell proliferation, migration, and aberrant metabolism, as well as increase tumor growth and metastasis in vivo. Herein, we summarized currently available research on the interaction between LncRNA FTX and associated molecules and signaling pathways in malignant tumors to better understand the biological roles of LncRNA FTX in cancer progression.

MEK nuclear localization promotes YAP stability via sequestering ß-TrCP in KRAS mutant cancer cells.

Tumours manage to survive the ablation of mutant KRAS, despite the development of KRAS-targeted drugs. Here we describe that inhibition of mutant KRAS promotes MEK nuclear localization as an alternative mechanism of KRAS-targeted drugs resistance. Tissue microarray analysis in colon tumours shows that aberrant MEK nuclear localization is closely related to YAP levels and tumour malignancy. MEK nuclear localization could sequester ß-TrCP from cytoplasmic inactive YAP, then stabilizing YAP. Mutant KRAS restrains MEK within the cytoplasm via IQGAP1, inhibiting MEK nuclear translocation. Trametinib, an allosteric MEK inhibitor, could prevent MEK nuclear localization and subsequently promote YAP degradation. In vitro and in vivo results suggests that inhibition of MEK nuclear localization by trametinib synergizes with KRAS knockdown or deltarasin treatment in suppressing the viability of KRAS mutant colon cancer cells. Our study provides new insights into the mechanisms of resistance to KRAS ablation, and suggests novel strategies for the treatment of KRAS-mutant colon cancers.

EGFR-PI3K-PDK1 pathway regulates YAP signaling in hepatocellular carcinoma: the mechanism and its implications in targeted therapy.

The epidermal growth factor receptor (EGFR) pathway and Hippo signaling play an important role in the carcinogenesis of hepatocellular carcinoma (HCC). However, the crosstalk between these two pathways and its implications in targeted therapy remains unclear. We found that the activated EGFR signaling could bypass RhoA to promote the expression of YAP(Yes-associated protein), the core effector of the Hippo signaling, and its downstream target Cyr61. Further studies indicated that EGFR signaling mainly acted through the PI3K-PDK1 (Phosphoinositide 3-kinase-Phosphoinositide-dependent kinase-1) pathway to activate YAP, but not the AKT and MAPK pathways. While YAP knockdown hardly affected the EGFR signaling. In addition, EGF could promote the proliferation of HCC cells in a YAP-independent manner. Combined targeting of YAP and EGFR signaling by simvastatin and the EGFR signaling inhibitors, including the EGFR tyrosine kinase inhibitor (TKI) gefitinib, the RAF inhibitor sorafenib and the MEK inhibitor trametinib, presented strong synergistic cytotoxicities in HCC cells. Therefore, the EGFR-PI3K-PDK1 pathway could activate the YAP signaling, and the activated EGFR signaling could promote the HCC cell growth in a YAP-independent manner. Combined use of FDA-approved inhibitors to simultaneously target YAP and EGFR signaling presented several promising therapeutic approaches for HCC treatment.

Down regulation of lincRNA-p21 contributes to gastric cancer development through Hippo-independent activation of YAP.

Long intergenic non-coding RNA p21 (lincRNA-p21), known as the direct transcriptional target of p53, was found down-regulated in several human solid tumors. However, little is known about the role of lincRNA-p21 in gastric cancer. The expression levels of lincRNA-p21 in tissue samples and cell lines were detected by qRT-PCR. MGC-803 and MKN-45 cells were transfected with siRNAs targeting lincRNA-p21 or control siRNAs to determine the effect of reduced lincRNA-p21 expression on tumorigenesis. We also overexpressed lincRNA-p21 in MGC-803 cells. Cell proliferation was measured by CCK-8 and Ethynyl-2-deoxyuridine (EdU) incorporation assays. Migration and invasion abilities of cells were measured by wound healing and transwell assay. We demonstrated that lincRNA-p21 was significantly reduced in gastric cancer tissues (p<0.001) compared with that in normal tissues and this lower level of lincRNA-p21 was significantly correlated with higher invasion depth grade (p=0.024), more distant metastasis (p=0.009) and advanced TNM stage (p=0.011). Further study revealed that knock down of lincRNA-p21 could promote malignant behavior of gastric cancer cells and induce epithelial to mesenchymal transition (EMT). Overexpressing lincRNA-p21 showed opposite effects. Moreover, knocking down lincRNA-p21 could elevate the expression of Yes associated protein (YAP), the core effector of Hippo signaling, by elevating mRNA levels and increasing its nucleus translocation instead of the canonical Hippo pathway. Overexpression experiments verified the regulation role of lincRNA-p21 in YAP expression. Collectively, these data suggest that lincRNA-p21 could serve as a potential biomarker and a vital therapeutic target in gastric cancer.

Acetylcholine acts through M3 muscarinic receptor to activate the EGFR signaling and promotes gastric cancer cell proliferation.

Acetylcholine (ACh), known as a neurotransmitter, regulates the functions of numerous fundamental central and peripheral nervous system. Recently, emerging evidences indicate that ACh also plays an important role in tumorigenesis. However, little is known about the role of ACh in gastric cancer. Here, we reported that ACh could be auto-synthesized and released from MKN45 and BGC823 gastric cancer cells. Exogenous ACh promoted cell proliferation in a does-dependent manner. The M3R antagonist 4-DAMP, but not M1R antagonist trihexyphenidyl and M2/4 R antagonist AFDX-116, could reverse the ACh-induced cell proliferation. Moreover, ACh, via M3R, activated the EGFR signaling to induce the phosphorylation of ERK1/2 and AKT, and blocking EGFR pathway by specific inhibitor AG1478 suppressed the ACh induced cell proliferation. Furthermore, the M3R antagonist 4-DAMP and darifenacin could markedly inhibit gastric tumor formation in vivo. 4-DAMP could also significantly enhance the cytotoxic activity of 5-Fu against the MKN45 and BGC823 cells, and induce the expression of apoptosis-related proteins such as Bax and Caspase-3. Together, these findings indicated that the autocrine ACh could act through M3R and the EGFR signaling to promote gastric cancer cells proliferation, targeting M3R or EGFR may provide us a potential therapeutic strategy for gastric cancer treatment.

[Study on inducing differentiation of human amniotic epithelial cells into insulin secreting cells in vitro].

OBJECTIVE: To investigate the differentiation of human amniotic epithelial cells (hAECs) into insulin secreting cells (ISCs) in vitro. METHODS: The hAECs were isolated from human amnion by trypsin digestion, and the phenotype of the isolated cells were identified by flow cytometry and immunocytochemical staining. The hAECs at passage 3 were treated with nicotinamide and N2 supplement to investigate their differentiation into ISCs. At different times after differentiation, the expression of insulin and beta2 microglobulin (beta2-MG) was determined by immunocytochemical staining, while the content of insulin in supernatant from cultured hAECs was detected by radioimmunoassay and the expressions of insulin, pancreatic and duodenal homeobox factor-1 (PDX-1) mRNA were detected by reverse transcriptase-polymerase chain reaction (RT-PCR). RESULTS: (1) hAECs expressed high percent of CD29, CD73, CD166 and CK19. (2) At 7, 14 and 21 days, the percentages of insulin-positive cells in induced groups were 74.00% +/- 1.73%, 75.33% +/- 1.15% (see symbol) 75.67% +/- 0.58% respectively, which were negative in control groups. (3) At 7, 14 and 21 days, contents of insulin in supernatant from induced groups were (328.47 +/- 3.22) microIU/ml, (332.26 +/- 1.22) microIU/ml and (329.68 +/- 2.57) microIU/ml respectively, they were significantly higher than those in control groups (All P < 0.01). (4) PDX-1 mRNA and beta2-MG were expressed before and after the induction of hAECs, but insulin mRNA was expressed only in the induced groups. CONCLUSION: hAECs can differentiate into ISCs, having the potential application for therapy of type I diabetes.