These data clearly demonstrate that the transcriptional control afforded by the cox-2 promoter is tumor-specific and is able to mitigate associated toxicity in normal tissue while maintaining therapeutic efficacy in the context of an ovarian cancer molecular chemotherapeutic approach.
These observations suggest that the interaction of COX-2 with p53 may cause p21-independent suppression of tumor cell growth upon flurbiprofen treatment.
Furthermore, another concept is emerging to indicate that prostaglandins (COX-2 products and mediators of classic inflammation) suppress host immunity against tumors.
To date, at least five mechanisms by which COX-2 contributes to tumorigenesis and the malignant phenotype of tumor cells have been identified, including: (1) inhibition of apoptosis; (2) increased angiogenesis; (3) increased invasiveness; (4) modulation of inflammation/immuno-suppression; and (5) conversion of procarcinogens to carcinogens.
Two distinct COXs have been identified: COX-1 which is constitutively expressed and COX-2 which is induced by different products such as tumor promoters or growth factors.
These in vitro and in vivo results suggest that selective COX-2 inhibitors enhance the effect of radiation on tumors that express COX-2 but not on COX-2-lacking tumors.
To further elucidate the mechanism responsible for increased levels of PGE(2) in colorectal tumors, we determined the amounts of mPGES and COX-2 in 18 paired samples (tumor and adjacent normal) of colorectal cancer.
Expression of Cox-2 and MDR1/Pgp170 was investigated in tumor specimens along with normal epithelium in breast cancer patients using immunohistochemisrty.
Since lung cancer patients were recruited mostly among smokers, who also have been found to exhibit significantly higher infection rate of Helicobacter pylori (HP) infection than non-smokers and, as since the HP-infected subjects show enhanced plasma levels of gastrin, we decided 1) to compare the seroprevalence of HP and the expression of its cytotoxin, CagA, in lung cancer patients with those in the age- and gender-matched controls without cancer: 2) to determine the gene expression for gastrin and its receptors (CCKB-R) in lung cancer, 3) to assess the gastrin levels in plasma bronchial lavage and in tumor tissue and 4) to examine the expression of cyclooxygenase (COX)-1 and COX-2 in cancer tissue resection margin and intact bronchial mucosa.
Immunohistochemistry of various types of brain tumors, including six glioblastomas, nine astrocytomas, six meningiomas, five medulloblastomas, four craniopharyngiomas, three ependymomas, three neurinomas, two oligodendrogliomas, two malignant lymphomas, two dysembryoplastic neuroepitherial tumors and one metastatic brain tumor showed PHS-2 staining in most cases.
A significant correlation between COX-2 and tumor vascularization (r(s)=0.450, P=.007) as well as between COX-2 and microvessel density with VEGF expression in tumor tissues was found (r(s)=0.450, P=.007; r(s)=0.620, P=.0001, respectively).
The observed over-expression of COX-2 gene in human urinary bladder and the concomitant increases in PG synthesis may explain, at least in part, the mechanism by which cigarette smoking influences the development of urothelial neoplasia.
LNCaP-COX-2 cells had increased secretion of vascular endothelial growth factor (VEGF) protein, suggesting that angiogenesis induced by COX-2 stimulates tumor growth in vivo.
COX-2 is expressed in a high percentage of a large series of primary endometrial tumors and its expression may be associated closely with parameters of tumor aggressiveness The possible prognostic role of COX-2 in endometrial carcinoma deserves further study.
COX-1 was similarly expressed in GC and MALT as in intact mucosa, while COX-2 mRNA was detected only in tumor tissue, being attenuated by H.pylori eradication in GC and abolished by this therapy in MALT-lymphoma.
COX-2 expression in stromal cells appears to have a role in tumor angiogenesis because tumor growth is attenuated when colon cancer cells are implanted in COX-2 knockout mice due to a decreased vascular supply to the tumors.