Branching development of early post-implantation human embryonic-like tissues in 3D stem cell culture.

Human embryonic stem cells (hESCs) have the intrinsic capacity to self-organize and generate patterned tissues. In vitro models that coax hESCs to form embryonic-like structures by modulating physical environments and priming with chemical signals have become a powerful tool for dissecting the regulatory mechanisms underlying early human development. Here we present a 3D suspension culture system of hESCs that can generate post-implantation, pre-gastrulation embryonic-like tissues in an efficient and controllable manner. The efficiency of the development of asymmetric tissues, which mimic the post-implantation, pre-gastrulation amniotic sac, was about 50% in the 3D suspension culture. Quantitative imaging profiling and unsupervised trajectory analysis revealed that hESC aggregates first entered into a transitional stage expressing Brachyury (or T), before their development branched into different paths to develop into asymmetric embryonic-like tissues, amniotic-like tissues, and mesodermal-like tissues, respectively. Moreover, the branching developmental trajectory of embryonic-like structures was affected by the initial cell seeding density or cluster size of hESCs. A higher percentage of amniotic-like tissues was observed under a small initial cell seeding density of hESCs. Conversely, a large initial cell seeding density of hESCs promoted the development of mesodermal-like tissues. Intermediate cell seeding densities of hESCs in the 3D suspension culture promoted the development of asymmetric embryonic-like tissues. Our results suggest that hESCs have the intrinsic capability to sense the initial cell population size, which in turn regulates their differentiation and self-organization into different embryonic-like tissues. Our 3D suspension culture thus provides a promising experimental tool to study the interplay between tissue topology and self-organization and progressive embryonic development using in vitro hESC-based models.

Resveratrol causes cell cycle arrest, decreased collagen synthesis, and apoptosis in rat intestinal smooth muscle cells.

One of the most difficult and treatment-resistant complications of Crohn's disease is the development of fibrotic intestinal strictures due to mesenchymal cell hyperplasia and collagen deposition. Resveratrol, a phytoalexin found in berries, peanuts, grapes, and red wine, has been shown to inhibit fibrosis in vasculature, heart, lung, kidney, liver, and esophagus in animal models. Resveratrol has also been shown to inhibit oxidation, inflammation, and cell proliferation and to decrease collagen synthesis in several cell types or animal models. The aim of this study was to determine whether resveratrol has antifibrotic effects on intestinal smooth muscle cells. Responses to resveratrol by cultured smooth muscle cells isolated from colons of untreated Lewis rats were examined; this rat strain is used in a model of Crohn's disease with prominent intestinal fibrosis. A relative decrease in cell numbers following treatment with 50 and 100 µM resveratrol was evident at 24 h (P ≤ 0.005). This effect was largely due to cell cycle arrest, with an increase in the percent of cells in S phase from 8 to 25-35% (P < 0.05). Cell viability was unchanged until 2-3 days of treatment when there was a 1.2- to 5.0-fold increase in the percent of apoptotic cells, depending on the assay (P < 0.05). Expression of collagen type I protein was decreased following treatment with resveratrol for 24 h (to 44 and 25% of control levels with 50 and 100 µM resveratrol, respectively; P < 0.05). Expression of procollagen types I and III mRNA was also decreased with resveratrol treatment. Resveratrol (50 µM) diminished the proliferative response to TGF-ß1 (P = 0.02) as well as IGF-I-stimulated collagen production (P = 0.02). Thus resveratrol decreases intestinal smooth muscle cell numbers through its effects on cell cycle arrest and apoptosis and also decreases collagen synthesis by the cells. These effects could be useful in preventing the smooth muscle cell hyperplasia and collagen deposition that characterize stricture formation in Crohn's disease.

A small molecule compound inhibits AKT pathway in ovarian cancer cell lines.

BACKGROUND AND OBJECTIVE: Overactivation of AKT1 and gene amplification of AKT2 are frequently detected in ovarian cancer. Activated AKT kinases provide a cell survival signal that may confer resistance to apoptosis induced by conventional therapies in cancer cells. Therefore, development of potent inhibitors that block AKT pathway is an attractive therapeutic strategy for treating ovarian carcinoma. METHODS: Ovarian cancer cell lines, A2780, MDAH2774, OVCAR-8, Caov-3, and normal murine fibroblasts (NIH3T3) were used. Cells were treated with different doses of a non-peptide small molecule compound, 9-methoxy-2-methylellipticinium acetate (termed API-59-OME) that potentially inhibit AKT pathway. Kinase assays and the phosphorylation of AKT, GSK-3alpha/beta, PDK1, ERK1/2, SGK, p38, FAK, EGFR, JAK2, PKC isoforms, and the cleavage of poly (ADP-ribose) polymerase (PARP) were examined in treated and untreated cell lines. Further, cells treated with API-59-OME were analyzed for induction of apoptosis using sub-G1 profile with propidium iodide staining. RESULTS: API-59-OME inhibited AKT kinase activity but did not inhibit ERK or JNK kinase activities in A2780, MDAH2774, and OVCAR-8 cell lines. API-59-OME did not reduce phosphorylation of other protein kinases in these cell lines. API-59-OME induced apoptosis and the cleavage of PARP in A2780, MDAH2774, and OVCAR-8 ovarian cancer cell lines that express elevated levels of phosphorylated AKT. In contrast, in Caov-3 and NIH3T3 cell lines, which lack constitutive AKT activity, API-59-OME only had minimal effect to induce apoptosis. CONCLUSION: These data suggest that API-59-OME may be a potent agent to target constitutively activated AKT pathway in ovarian cancer cells.

Modulation of Janus kinase 2 by p53 in ovarian cancer cells.

The constitutive activation of the Janus kinase 2 (JAK2) and mutation of the p53 tumor suppressor are both detected in human cancer. We examined the potential regulation of JAK2 phosphorylation by wild-type (wt) p53 in human ovarian cancer cell lines, Caov-3 and MDAH2774, which harbor mutant form of p53 tumor suppressor gene and high levels of phosphorylated JAK2. The wt p53 gene was re-introduced into the cells using an adenovirus vector. In addition to wt p53, mutant p53 22/23, mutant p53-175, and NCV (negative control virus) were introduced into the cells in the control groups. Expression of wt p53, but not that of p53-175 mutant, diminished JAK2 tyrosine phosphorylation in MDAH2774 and Caov-3 cell lines. Expression of wt p53 or p53 22/23 mutant did not cause a reduction in the phosphorylation of unrelated protein kinases, ERK1 and ERK2 (ERK1/2). The inhibition of JAK2 tyrosine phosphorylation can be reversed by tyrosine phosphatase inhibitor, sodium orthovanadate. Protein tyrosine phosphatase 1-B levels increased with introduction of wt p53 and may be involved in the dephosphorylation of JAK2. These findings present a possible p53-dependent cellular process of modulating JAK2 tyrosine phosphorylation in ovarian cancer cell lines.

[Transcriptional inactivation of RASSF1A in lung cancer and its clinical significance].

OBJECTIVE: To explore the relationship between the transcriptional expression of RASSF1A (Ras association domain family 1A gene) and oncogenesis and development of lung cancer. METHOD: RT-PCR was used to detect the expression of RASSF1A mRNA in 47 human lung cancer tissues and matched 47 non-cancer tissues. RESULTS: (1). The RASSF1A mRNA was identified in all non-cancer tissues but not found in 53.2% carcinoma tissues. (2). The rate of loss of RASSF1A mRNA was significantly higher in the patients with positive lymph node metastasis (70.4%) than in those without lymph node metastasis (30.0%) (P < 0.01). (3). Much more frequent in advanced tumor tissues, loss of RASSF1A mRNA was correlated with TNM stage (P < 0.05). (4). No significant association of abnormal RASSF1A expression was identified with histological type, differentiation grade of tumors or age, sex, and smoking index of the patients (all P > 0.05). CONCLUSION: RASSF1A is one of the new candidates of tumor suppressor genes. Loss or abnormal down-regulation of RASSF1A mRNA is a frequent event in lung carcinogenesis, which may play an important role in the malignant progression and prognosis of lung cancer.

[Expression of different RASSF1 transcripts and its clinical significance in lung carcinoma].

OBJECTIVE: To evaluate the expression of three different RASSF1 transcripts and its clinical significance in lung carcinomas. METHODS: The mRNA expression of RASSF1A, RASSF1B and RASSF1C was detected by RT-PCR in 51 human lung cancer tissues and 51 matched normal tissues. RESULTS: 1. The mRNA expression of three RASSF1 transcripts was detectable in all non-cancer tissues. However, high rate of expression loss of RASSF1A and RASSF1B existed in lung cancer tissues, which was 53.2% (2851) and 37.3% (19/51), respectively. RASSF1C was expressed in all of the tumor tissues. 2. Loss or abnormal down-regulation of RASSF1A was positively related with lymph node metastasis and TNM stage (P < 0.05) and 3. RASSF1B and RASSF1C mRNA expression was not correlated with TNM stage, histological type, differentiation grade or smoking index. CONCLUSION: There is a significant expression difference among the three RASSF1 transcripts in lung carcinoma. RASSF1A, closely associated with lymph metastasis and TNM stage of lung carcinoma, should be a new tumor suppressor gene.

[Expression of lysyl oxidase gene in upper digestive tract carcinomas and its clinical significance].

BACKGROUND & OBJECTIVE: Lysyl oxidase(LO), one of newly discovered candidate of tumor suppressor genes, was reported that its expression was closely associated with recurrence and metastasis of breast and prostate carcinomas. However, till now there was no report evaluating the relationship between this gene expression and relapse or metastasis of upper digestive tract carcinomas. This study was designed to explore the relationship between the expression of LO gene and recurrence as well as metastasis of malignant upper digestive tract tumors such as esophageal, cardiac, and gastric cancers. METHOD: LO expression in esophageal, cardiac, and gastric cancer was determined by reverse transcriptase polymerase chain reaction (RT-PCR). RESULTS: RT-PCR amplification demonstrated that the expression rate was 42.1% (16/38), 42.9% 9(9/21), and 28.0% (7/25) in esophageal, cardiac, and gastric cancers, respectively. Furthermore, the expression rate of LO mRNA was lower in the tumor tissues with lymph nodes metastasis. And this was also observed in tumor with deep muscular layer infiltration(P < 0.05). In contrast, the reduced expression of the LO gene had no relation to histological classification, invasion pattern, tumor size, and number of metastasis lymph nodes(P > 0.05). CONCLUSIONS: These findings suggest that LO gene may play an important role in metastasis of esophageal, cardiac, and gastric carcinomas.

p53 regulates Stat3 phosphorylation and DNA binding activity in human prostate cancer cells expressing constitutively active Stat3.

Constitutive activation of the signal transducer and activator of transcription 3 (Stat3) and mutation of the p53 are both commonly detected in human prostate cancer cells. We sought to investigate whether there is functional regulation of Stat3 by wild-type (wt) p53. Our results demonstrate that expression of wt p53 but not mutant p53 significantly reduced tyrosine phosphorylation of Stat3 and inhibited Stat3 DNA binding activity in both DU145 and Tsu prostate cancer cell lines that express constitutively active Stat3. Expression of the p53 downstream target, p21(WAF-1), did not have any inhibitory effect on Stat3 phosphorylation. Wt p53 but not p21(WAF-1) induced dramatic apoptosis in these prostate cancer cells. Expression of wt p53 did not cause a reduction of phosphorylation-independent Stat3 protein and reduction of phosphorylation of three unrelated protein kinases, ERK1, ERK2 (ERK1/2), and AKT. Interestingly, p53-dependent apoptosis occurred in the presence of high levels of phosphorylated AKT and ERK1/2 in both DU145 and Tsu prostate cancer cells. Further, we evaluated a series of established human prostate, breast, and ovarian cancer cell lines and found that all cancer cell lines expressing constitutively active Stat3, only harbor mutated or deleted p53. One implication of these results is that the anti-proliferative activities of p53 may not be compatible with the constitutive Stat3 signal in cancer cells.

Dysfunctional apoptosome activation in ovarian cancer: implications for chemoresistance.

Alterations in the regulation of apoptosis may contribute to the pathogenesis of cancer and resistance of tumor cells to chemotherapy. In mammalian cells, nonreceptor-mediated apoptosis occurs predominantly via assembly of a cytochrome c-dependent apoptosome complex containing caspase-9 and apoptotic protease-activating factor-1 (Apaf-1). We show here that cytosolic extracts from human ovarian carcinoma cell lines and primary ovarian tumor samples are deficient in their ability to activate procaspase-9 in the presence of cytochrome c and dATP when compared with control extracts. SKOV3, a human ovarian carcinoma cell line with diminished apoptosome activity, was significantly more resistant to chemotherapy-induced apoptosis than cell lines with functional Apaf-1 activity. This dysfunctional apoptosome activity was not explained by reduced expression levels of caspase-9 or Apaf-1. Moreover, expression levels of known inhibitors of the apoptosome, including heat shock protein 70, heat shock protein 90, or X-linked inhibitor of apoptosis, did not correlate with functional activity of the apoptosome. SKOV3, an ovarian cancer cell line with dysfunctional apoptosome activity, retains the ability to form the Apaf-1 oligomer; however, there is a diminished amount of caspase-9 in the apoptosome. The reduction in the amount of caspase-9 in the apoptosome in the SKOV3 cell line was associated with diminished caspase-3 activity. Dysfunctional apoptosome activation may contribute both to the pathogenesis of ovarian carcinoma and to chemoresistance.

Modulation of signal transducer and activator of transcription 3 activities by p53 tumor suppressor in breast cancer cells.

The constitutive activation of the Stat3 oncogene product and mutation of the p53 tumor suppressor are both frequently detected in human breast cancer. We sought to determine whether there is functional regulation of Stat3 by wild-type (wt) p53. We demonstrate that expression of wt p53, but not mutant p53, significantly diminished phosphorylation of Stat3, reduced Stat3 DNA binding activity, and inhibited Stat3-dependent transcriptional activity in breast cancer cells expressing constitutively active Stat3. Expression of wt p53 did not cause a reduction in the phosphorylation of three unrelated protein kinases in other signal transduction pathways, AKT, extracellular signal-regulated kinase (ERK)1, and ERK2 or a reduction of phosphorylation of epidermal growth factor receptor. Furthermore, the expression of the p53 downstream target, p21(WAF-1), did not have an inhibitory effect on Stat3 phosphorylation. Wt p53 also induced significant apoptosis in breast cancer cell lines that express constitutively active Stat3. Interestingly, the p53-dependent apoptosis occurred in the presence of high levels of phosphorylated AKT and ERK1/2. Therefore, these findings demonstrate a novel p53-dependent cellular process that regulates Stat3 phosphorylation and activity.