Overexpression of PrPc,combined with MGr1‐Ag/37LRP,is predictive of poor prognosis in gastric cancer

Prion protein (PrPc) has been previously reported to be involved in gastric cancer (GC) development and progression. However, the association between expression of PrPc and GC prognosis is yet poorly characterized. In the present study, the expressions of PrPc and MGr1‐Ag/37LRP, a protein interacting with PrPc, were detected using the tissue microarray technique and immunohistochemical method to compare clinicopathological parameters of 238 GC patients. We found that the expressions of PrPc and MGr1‐Ag/37LRP were upregulated in GC lesions compared with their expressions in adjacent noncancerous tissues (p < 0.01). High expression of PrPc was detected in 37.39% (89/238) of GC patients and positively correlated with the expression of MGr1‐Ag/37LRP (r = 0.532, p < 0.001). PrPc expression was associated with a number of clinicopathological parameters including depth of invasion and lymph node metastasis of the tumor (p < 0.001). High expression of PrPc brought a poorer prognosis than low PrPc expression. Moreover, GC patients with high level of PrPc and high level of MGr1‐Ag/37LRP had the poorest prognosis. Multivariate survival analysis suggested that, along with other parameters, combined expression of PrPc and MGr1‐Ag/37LRP was independent prognostic factors for GC patients. These data indicates that overexpression of PrPc, combined with MGr1‐Ag/37LRP, is predictive of poor prognosis in GC and thereby could be used to guide the clinical decision.     

MGr1‐Ag/37LRP induces cell adhesion‐mediated drug resistance through FAK/PI3K and MAPK pathway in gastric cancer

It is well known that tumor microenvironment plays a vital role in drug resistance and cell adhesion‐mediated drug resistance (CAM‐DR), a form of de novo drug resistance. In our previous study, we reported that MGr1‐Ag/37LRP ligation‐induced adhesion participated in protecting gastric cancer cells from a number of apoptotic stimuli caused by chemotherapeutic drugs. Further study suggested that MGr1‐Ag could prompt CAM‐DR through interaction with laminin. However, the MGr1‐Ag‐initiated intracellular signal transduction pathway is still unknown. In this study, our experimental results showed that gastric cancer MDR cell lines mediated CAM‐DR through upregulation of Bcl‐2 by MGr1‐Ag interaction with laminin. Further study found that, as a receptor of ECM components, MGr1‐Ag/37LRP may activate the downstream signal pathway PI3K/AKT and MAPK/ERK through interaction with phosphorylated FAK. Moreover, the sensitivity to chemotherapeutic drugs could be significantly enhanced by inhibiting MGr1‐Ag/37LRP expression through mAbs, siRNA, and antisense oligonucleotide. According to these results, we concluded that the FAK/PI3K and MAPK signal pathway plays an important role in MGr1‐Ag‐mediated CAM‐DR in gastric cancer. MGr1‐Ag/37LRP might be a potential effective reversal target to MDR in gastric cancer.     

Single nucleotide polymorphisms in the hypoxia‐inducible factor‐1 gene and colorectal cancer risk

With an incidence of about 300 000 new cases colorectal cancer (CRC) is the second leading cause of cancer‐related death in Europe and the United States. Environmental and genetic factors influence CRC risk. Hypoxia‐inducible factor‐1 (HIF‐1), a heterodimeric protein composed of two subunits, HIF‐1 alpha and HIF‐1 beta, plays a critical role in oxygen homeostasis and is involved in angiogenesis and cell proliferation. The gene for the HIF‐1 alpha subunit (HIF1A) carries two common missense mutations—P582S (rs11549465) and A588T (rs11549467)—which both have been related to increased trans‐activation capacity of HIF1A. In our case–control study we investigated the association between these polymorphisms and CRC risk. We investigated 381 patients with histologically confirmed CRC and 2156 control subjects. HIF1A genotypes were determined by exonuclease (TaqMan) assays. For determination of microvessel density (MVD) tumor sections were stained using a mouse monoclonal antibody recognizing the pan‐endothelial marker CD31. In a multivariate logistic regression analysis including age and sex neither the HIF1A 582S allele (Odds ratio: 1.204; 95% confidence interval 0.911–1.592; P = 0.193) nor the 588T allele was significantly associated with CRC (Odds ratio: 0.851; 95% confidence interval 0.444–1.631; P = 0.626). However, in an exploratory analysis, the HIF1A 588T allele was associated with tumor localization (P = 0.016) and tumor size (P = 0.003). MVD was similar in tumors of patients carrying HIF1A 588T allele and patients without this rare allele. We conclude that functional polymorphisms in the HIF1A gene do not modify CRC risk but maybe associated with clinic‐pathological features of the disease. © 2010 Wiley‐Liss, Inc.     

Norepinephrine induces VEGF expression and angiogenesis by a hypoxia‐inducible factor‐1α protein‐dependent mechanism

A growing number of studies have demonstrated that physiological factors can influence the progression of several cancers via cellular immune function, angiogenesis and metastasis. Recently, stress‐induced catecholamines have been shown to increase the expression of various cancer progressive factors, including vascular endothelial growth factor (VEGF), matrix metalloproteinases and interleukins. However, a detailed mechanism remains to be identified. In this study, we investigated the role of adrenergic receptors and hypoxia‐inducible factor (HIF)‐1α protein in catecholamine‐induced VEGF expression and angiogenesis. Treatment of the cells with norepinephrine (NE) or isoproterenol induced VEGF expression and HIF‐1α protein amount in a dose‐dependent manner. Induction of VEGF expression by NE was abrogated when the cells were transfected with HIF‐1α–specific siRNA. Similarly, adenylate cyclase activator forskolin and cyclic AMP‐dependent protein kinase A inhibitor H‐89 enhanced and decreased HIF‐1α protein amount, respectively. More importantly, conditioned medium of NE‐stimulated cancer cells induced angiogenesis in a HIF‐1α protein–dependent manner. In addition, pretreatment of cells with propranolol, a β‐adrenergic receptor (AR) blocker, completely abolished induction of VEGF expression and HIF‐1α protein amount by NE in all of the tested cancer cells. However, treatment with the α1‐AR blocker prazosin inhibited NE‐induced HIF‐1α protein amount and angiogenesis in SK‐Hep1 and PC‐3 but not MDA‐MB‐231 cells. Collectively, our results suggest that ARs and HIF‐1α protein have critical roles in NE‐induced VEGF expression in cancer cells, leading to stimulation of angiogenesis. These findings will help to understand the mechanism of cancer progression by stress‐induced catecholamines and design therapeutic strategies for cancer angiogenesis.     

2‐Methoxyestradiol induced bax phosphorylation and apoptosis in human retinoblastoma cells via p38 MAPK activation

Retinoblastoma (Rb) is a common childhood intraocular cancer that affects approximately 300 children each year in the United States alone. 2‐Methoxyestradiol (2ME), an endogenous metabolite of 17‐β‐estradiol that dose not bind to nuclear estrogen receptor, exhibits potent apoptotic activity against rapidly growing tumor cells. Here, we report that 2ME induction of apoptosis was demonstrated by early fragmented DNA after 48 h of incubation with 10 µM 2ME in Rb cell lines. Subsequently, a decrease of proliferation was observed in a time‐ and dose‐dependent manner. Further analysis of the mechanism indicates that p38 kinase plays a critical role in 2ME‐induced apoptosis in Y79 cells, even though ERK was also activated by 2ME under the same conditions. Activation of p38 kinase also mediates 2ME induced Bax phosphorylated at Thr¹⁶⁷ after a 6 h treatment of 2ME, which in turn prevents formation of the Bcl‐2‐Bax heterodimer. Both p38 specific inhibitor, SB 203580, or p38 knockdown by specific siRNA, blocked 2ME induction of Bax phosphorylation. Furthermore, only transiently transfected mutant BaxT167A, but not Bax S163A, inhibited 2ME‐induced apoptosis. In summary, our data suggest that 2ME induces apoptosis in human Rb cells by causing phosphorylation of p38 Mitogen‐activated protein kinase (MAPK), which appears to be correlated with phosphorlation of Bax. This understanding of 2ME's ability may help develop it as a promising therapeutic candidate by inducing apoptosis in a Rb. © 2011 Wiley Periodicals, Inc.     

Hepatocyte growth factor induces hypoxia‐related interleukin‐8 expression in lung adenocarcinoma cells

Rapid growth of cancer cells often creates insufficient supply of oxygen and nutrients in the tumour nest. The frequent detection of hypoxia‐inducible factor (HIF) and interleukin‐8 (IL‐8) in afflicted tissues suggests that IL‐8 expression could be associated with elevated levels of HIF. Recently, we found that hypoxia also upregulated the expression of hepatocyte growth factor (HGF) in lung adenocarcinoma (LAD) cells. However, the relationship between HGF and IL‐8 has not been investigated in LAD cells. In this study, we found that HGF induced IL‐8 expression in LAD. Interestingly, hypoxia also increased the level of prostaglandin F_2α (PGF_2α), a product of dihydrodiol dehydrogenase (DDH). When expression of DDH was suppressed by siRNA, the levels of PGF_2α, HGF and IL‐8 were reduced; however, their levels returned to normal after DDH was reintroduced. These data suggest that hypoxia induces biosynthesis of PGF_2α, which then activates HGF and IL‐8 expression. The results provide a reasonable explanation of how PGF_2α, HGF and IL‐8 exert their effects on cancer cell metastasis. © 2009 Wiley‐Liss, Inc.     

Hypoxia/pseudohypoxia‐mediated activation of hypoxia‐inducible factor‐1α in cancer

Since the first identification of hypoxic cells in sections of carcinomas in the 1950s, hypoxia has been known as a central hallmark of cancer cells and their microenvironment. Indeed, hypoxia benefits cancer cells in their growth, survival, and metastasis. The historical discovery of hypoxia‐inducible factor‐1α (HIF1A) in the early 1990s had a great influence on the field as many phenomena in hypoxia could be explained by HIF1A. However, not all regions or types of tumors are necessarily hypoxic. Thus, it is difficult to explain whole cancer pathobiology by hypoxia, especially in the early stage of cancer. Upregulation of glucose metabolism in cancer cells has been well known. Oxygen‐independent glycolysis is activated in cancer cells even in the normoxia condition, which is known as the Warburg effect. Accumulating evidence and recent advances in cancer metabolism research suggest that hypoxia‐independent mechanisms for HIF signaling activation is a hallmark for cancer. There are various mechanisms that generate pseudohypoxic conditions, even in normoxia. Given the importance of HIF1A for cancer pathobiology, the pseudohypoxia concept could shed light on the longstanding mystery of the Warburg effect and accelerate better understanding of the diverse phenomena seen in a variety of cancers.     

Overexpression of hypoxia‐inducible factor 1 alpha impacts FoxP3 levels in mycosis fungoides—Cutaneous T‐cell lymphoma: Clinical implications

Mycosis fungoides (MF) is the most common variant of primary cutaneous T‐cell lymphoma, and decreased forkhead box P3 (FoxP3) expression has been reported in MF late stages. Hypoxia‐inducible factor 1 alpha (HIF‐1α) may regulate FoxP3 expression; however, it is unknown whether HIF‐1α is expressed in the CD4⁺ T cells of MF patients and how it could affect the expression of FoxP3. Therefore, we evaluated the expression of HIF‐1α and FoxP3 in CD4⁺ T cells obtained from the skin lesions of MF patients. We found increased cell proliferation and an increase in CD4⁺ T cells with an aberrant phenotype among early stage MF patients. HIF‐1α was overexpressed in these CD4⁺ T cells. In addition, we found a decrease in the percentage of FoxP3⁺ cells both in the skin of MF patients, when compared with control skin samples, and with disease progression. In addition, a negative correlation was established between HIF‐1α and FoxP3 expression. Skin HIF‐1α expression in MF patients correlated with the extent of the affected area and increased with the disease progression. Finally, we showed that ex vivo inhibition of HIF‐1α degradation increases the percentage of FoxP3⁺ T cells in skin lesions. Our results suggest that overexpression of HIF‐1α affects the levels of FoxP3 in MF patients, which could have relevant implications in terms of disease outcome.     

Stomatin‐like protein 2 inhibits cisplatin‐induced apoptosis through MEK/ERK signaling and the mitochondrial apoptosis pathway in cervical cancer cells

Stomatin‐like protein 2 (STOML2 or SLP‐2) is an oncogenic anti‐apoptotic protein that is upregulated in several types of cancer, including cervical cancer. However, the mechanisms responsible for the SLP‐2 anti‐apoptotic function remain poorly understood. Here, we show that siRNA‐mediated SLP‐2 suppression decreases growth of human cervical cancer HELA and SIHA cells, and increases cisplatin‐induced apoptosis through activation of MEK/ERK signaling and suppression of the mitochondrial pathway. The inhibition of the mitochondrial pathway is mediated by increasing the mitochondrial Ca²⁺ concentration and mitochondrial membrane potential, thereby downregulating p‐MEK and p‐ERK levels, upregulating the Bax/Bcl‐2 ratio, increasing cytochrome C release from mitochondria into the cytosol, and upregulating levels of cleaved‐caspase 9, cleaved‐caspase 3, and cleaved poly ADP‐ribose polymerase (PARP). Overexpression of SLP‐2 using adenovirus‐STOML2 has the opposite effect: it upregulates p‐MEK and p‐ERK and downregulates the Bax/Bcl‐2 ratio and levels of cleaved‐caspase 9 to caspase 9, cleaved‐caspase 3 to caspase 3, and cleaved‐PARP to PARP in cisplatin‐treated cells. These data show that SLP‐2 inhibits cisplatin‐induced apoptosis by activating the MEK/ERK signaling and inhibiting the mitochondrial apoptosis pathway in cervical cancer cells.