Cancer research
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Comparative Study
Defects of DNA mismatch repair in human prostate cancer.
Loss of mismatch repair (MMR) function leads to the accumulation of errors that normally occur during DNA replication, resulting in genetic instability. Germ-line mutations of MMR genes in the patients with hereditary nonpolyposis colorectal cancer lead to inactivation of MMR protein functions, and the defects of MMR are well correlated to the high rate of microsatellite instability in their tumors. Previous studies (T. ⋯ In contrast to hereditary nonpolyposis colorectal cancer, characterized by defects predominantly in MLH1 and MSH2, the samples we examined showed more tumor foci with loss of PMS1 and PMS2. PMS1, which is only expressed in the basal cells in normal glands, is conspicuously absent in most prostate cancer. From these results, we conclude that there are defects of MMR genes in human prostate cancer.
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Among women, the A2 allele of CYP17 has been associated with elevated levels of endogenous steroid hormones; however, it does not seem to be a strong independent risk factor for breast cancer. We assessed the association between the A2 allele of CYP17 and invasive endometrial cancer risk in a case-control study nested within the Nurses' Health Study cohort (cases: n = 184; controls: n = 554). We also evaluated whether endometrial cancer risk associated with CYP17 genotype was modified by established endometrial cancer risk factors. ⋯ Among 165 controls, we did not observe women with the A2 allele to have significantly elevated levels of any steroid hormone fraction. When these women were combined and analyzed with those women on whom we had previously examined the relationship between CYP17 genotype and circulating hormone levels (total n = 469), only modest associations were observed for the A2/A2 genotype and steroid hormone fractions estrone (versus A1/A1 genotype: +10.9%; P = 0.05) and estradiol (+8.5%; P = 0.17). These data suggest that the A2 allele of CYP17 decreases endometrial cancer risk, but has only weak effects on endogenous estrogen levels among postmenopausal women.
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Bone cancer pain most commonly occurs when tumors originating in breast, prostate, or lung metastasize to long bones, spinal vertebrae, and/or pelvis. Primary and metastatic cancers involving bone account for approximately 400,000 new cancer cases per year in the United States alone, and >70% of patients with advanced breast or prostate cancer have skeletal metastases. Whereas pain resulting from bone cancer can dramatically impact an individual's quality of life, very little is known about the mechanisms that generate and maintain this pain. ⋯ Results indicated that osteoprotegerin treatment halted further bone destruction, reduced ongoing and movement-evoked pain, and reversed several aspects of the neurochemical reorganization of the spinal cord. Thus, even in advanced stages of bone cancer, ongoing osteoclast activity appears to be involved in the generation and maintenance of ongoing and movement-evoked pain. Blockade of ongoing osteoclast activity appears to have the potential to reduce bone cancer pain in patients with advanced tumor-induced bone destruction.
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JC virus (JCV) is a neurotropic polyomavirus infecting greater than 70% of the human population worldwide during early childhood. Replication of JCV in brains of individuals with impaired immune systems results in the fatal demyelinating disease, progressive multifocal leukoencephalopathy (PML). Furthermore, JCV possesses an oncogenic potential and induces development of various neuroectodermal origin tumors including medulloblastomas and glioblastomas in experimental animals. ⋯ We performed gene amplification techniques using a pair of primers that recognize the JCV DNA sequence, and we demonstrated the presence of the viral early sequence in 49 (69%) of 71 samples. More importantly, our results from immunohistochemistry analysis revealed expression of JCV T-antigen in the nuclei of tumor cells in 28 (32.9%) of 85 tested samples. These observations, along with earlier in vitro and in vivo data on the transforming ability of this human neurotropic virus invite additional studies to re-evaluate the role of JCV in the pathogenesis of human brain tumors.
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The antitumor drug adozelesin is a potent cytotoxic DNA-damaging agent. Here we determined how adozelesin affects chromosomal DNA replication at a molecular level in a yeast model system and examined the influence of checkpoint kinase genes, the human homologues of which are mutated in cancer. Analysis of replication intermediates using two-dimensional gel electrophoresis showed that adozelesin inhibited the activity of a replication origin and stalled replication fork progression through chromosomal DNA at the origin. ⋯ In contrast to the inhibition of the active replication origin by adozelesin, normally silent origins present in the same chromosome were activated by adozelesin in rad53 and mec1 mutant cells. Thus, an antitumor drug that damages DNA can induce an abnormal replication pattern in a chromosome by activating silent origins, depending upon defects in yeast checkpoint kinase genes, the homologues of which are mutated in cancer. Implications of an abnormal replication pattern for the epigenetic regulation of gene expression are discussed.