MicroRNAs (miRNAs) are endogenous noncoding RNAs, which negatively regulate gene expression. To determine genomewide miRNA DNA copy number abnormalities in cancer, 283 known human miRNA genes were ...analyzed by high-resolution arraybased comparative genomic hybridization in 227 human ovarian cancer, breast cancer, and melanoma specimens. A high proportion of genomic loci containing miRNA genes exhibited DNA copy number alterations in ovarian cancer (37.1%), breast cancer (72.8%), and melanoma (85.9%), where copy number alterations observed in >15% tumors were considered significant for each miRNA gene. We identified 41 miRNA genes with gene copy number changes that were shared among the three cancer types (26 with gains and 15 with losses) as well as miRNA genes with copy number changes that were unique to each tumor type. Importantly, we show that miRNA copy changes correlate with miRNA expression. Finally, we identified high frequency copy number abnormalities of Dicerl, Argonaute2, and other miRNA-associated genes in breast and ovarian cancer as well as melanoma. These findings support the notion that copy number alterations of miRNAs and their regulatory genes are highly prevalent in cancer and may account partly for the frequent miRNA gene deregulation reported in several tumor types.
MicroRNAs (miRNA) are approximately 22-nucleotide noncoding RNAs that negatively regulate protein-coding gene expression in a sequence-specific manner via translational inhibition or mRNA ...degradation. Our recent studies showed that miRNAs exhibit genomic alterations at a high frequency and their expression is remarkably deregulated in ovarian cancer, strongly suggesting that miRNAs are involved in the initiation and progression of this disease. In the present study, we performed miRNA microarray to identify the miRNAs associated with chemotherapy response in ovarian cancer and found that let-7i expression was significantly reduced in chemotherapy-resistant patients (n = 69, P = 0.003). This result was further validated by stem-loop real-time reverse transcription-PCR (n = 62, P = 0.015). Both loss-of-function (by synthetic let-7i inhibitor) and gain-of-function (by retroviral overexpression of let-7i) studies showed that reduced let-7i expression significantly increased the resistance of ovarian and breast cancer cells to the chemotherapy drug, cis-platinum. Finally, using miRNA microarray, we found that decreased let-7i expression was significantly associated with the shorter progression-free survival of patients with late-stage ovarian cancer (n = 72, P = 0.042). This finding was further validated in the same sample set by stem-loop real-time reverse transcription-PCR (n = 62, P = 0.001) and in an independent sample set by in situ hybridization (n = 53, P = 0.049). Taken together, our results strongly suggest that let-7i might be used as a therapeutic target to modulate platinum-based chemotherapy and as a biomarker to predict chemotherapy response and survival in patients with ovarian cancer.
Data on the efficacy of bilateral prophylactic mastectomy for breast cancer risk reduction in women with BRCA1 and BRCA2 (BRCA1/2) mutations are limited, despite the clinical use of this ...risk-management strategy. Thus, we estimated the degree of breast cancer risk reduction after surgery in women who carry these mutations.
Four hundred eighty-three women with disease-associated germline BRCA1/2 mutations were studied for the occurrence of breast cancer. Cases were mutation carriers who underwent bilateral prophylactic mastectomy and who were followed prospectively from the time of their center ascertainment and their surgery, with analyses performed for both follow-up periods. Controls were BRCA1/2 mutation carriers with no history of bilateral prophylactic mastectomy matched to cases on gene, center, and year of birth. Both cases and controls were excluded for previous or concurrent diagnosis of breast cancer. Analyses were adjusted for duration of endogenous ovarian hormone exposure, including age at bilateral prophylactic oophorectomy if applicable.
Breast cancer was diagnosed in two (1.9%) of 105 women who had bilateral prophylactic mastectomy and in 184 (48.7%) of 378 matched controls who did not have the procedure, with a mean follow-up of 6.4 years. Bilateral prophylactic mastectomy reduced the risk of breast cancer by approximately 95% in women with prior or concurrent bilateral prophylactic oophorectomy and by approximately 90% in women with intact ovaries.
Bilateral prophylactic mastectomy reduces the risk of breast cancer in women with BRCA1/2 mutations by approximately 90%.
Breast and Ovarian Cancer Wooster, Richard; Weber, Barbara L
The New England journal of medicine,
06/2003, Letnik:
348, Številka:
23
Journal Article
Recenzirano
Odprti dostop
Breast and ovarian cancers are among the most common cancers in women. It is known that a woman is at higher risk for breast or ovarian cancer if a family member has had the disease. This article in ...the Genomic Medicine series provides up-to-date information on the heritable factors associated with these tumors.
Despite years of intensive study and substantial progress in understanding susceptibility to breast and ovarian cancer, these diseases remain important causes of death in women. However, several recent critical advances — sequencing of the human genome and the development of high-throughput techniques for identifying DNA-sequence variants, changes in copy numbers, and global expression profiles — have dramatically accelerated the pace of research aimed at preventing and curing these diseases. We review some of the important discoveries in the genetics of breast and ovarian cancer, ongoing studies to isolate additional susceptibility genes, and early work on molecular profiling involving microarrays.
Susceptibility . . .
Oncogenic mutations in the serine/threonine kinase B-RAF (also known as BRAF) are found in 50-70% of malignant melanomas. Pre-clinical studies have demonstrated that the B-RAF(V600E) mutation ...predicts a dependency on the mitogen-activated protein kinase (MAPK) signalling cascade in melanoma-an observation that has been validated by the success of RAF and MEK inhibitors in clinical trials. However, clinical responses to targeted anticancer therapeutics are frequently confounded by de novo or acquired resistance. Identification of resistance mechanisms in a manner that elucidates alternative 'druggable' targets may inform effective long-term treatment strategies. Here we expressed ∼600 kinase and kinase-related open reading frames (ORFs) in parallel to interrogate resistance to a selective RAF kinase inhibitor. We identified MAP3K8 (the gene encoding COT/Tpl2) as a MAPK pathway agonist that drives resistance to RAF inhibition in B-RAF(V600E) cell lines. COT activates ERK primarily through MEK-dependent mechanisms that do not require RAF signalling. Moreover, COT expression is associated with de novo resistance in B-RAF(V600E) cultured cell lines and acquired resistance in melanoma cells and tissue obtained from relapsing patients following treatment with MEK or RAF inhibitors. We further identify combinatorial MAPK pathway inhibition or targeting of COT kinase activity as possible therapeutic strategies for reducing MAPK pathway activation in this setting. Together, these results provide new insights into resistance mechanisms involving the MAPK pathway and articulate an integrative approach through which high-throughput functional screens may inform the development of novel therapeutic strategies.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Tumor growth results in hypoxia. Understanding the mechanisms of gene expression reprogramming under hypoxia may provide important clues to cancer pathogenesis. We studied miRNA genes that are ...regulated by hypoxia in ovarian cancer cell lines by TaqMan miRNA assay containing 157 mature miRNAs. MiR-210 was the most prominent miRNA consistently stimulated under hypoxic conditions. We provide evidence for the involvement of the HIF signaling pathway in miR-210 regulation. Biocomputational analysis and in vitro assays demonstrated that e2f transcription factor 3 (e2f3), a key protein in cell cycle, is regulated by miR-210. E2F3 was further confirmed to be downregulated at the protein level upon induction of miR-210. Importantly, we found remarkably high frequency of miR-210 gene copy deletions in ovarian cancer patients (64%, n=114) and that gene copy number correlates with miR-210 expression levels. Taken together, our results indicate that miR-210 plays a crucial role in tumor onset as a key regulator of the hypoxia response and provide evidence for a link between hypoxia and the regulation of cell cycle.
Bilateral prophylactic oophorectomy (BPO) is widely used for cancer risk reduction in women with BRCA1/2 mutations. Many premenopausal women choose to take hormone replacement therapy (HRT) after ...undergoing BPO to abrogate immediate symptoms of surgically-induced menopause. Thus, we evaluated whether the breast cancer risk reduction conferred by BPO in BRCA1/2 mutation carriers is altered by use of post-BPO HRT.
We identified a prospective cohort of 462 women with disease-associated germline BRCA1/2 mutations at 13 medical centers to evaluate breast cancer risk after BPO with and without HRT. We determined the incidence of breast cancer in 155 women who had undergone BPO and in 307 women who had not undergone BPO on whom we had complete information on HRT use. Postoperative follow-up was 3.6 years.
Consistent with previous reports, BPO was significantly associated with breast cancer risk reduction overall (hazard ratio HR = 0.40; 95%CI, 0.18 to 0.92). Using mutation carriers without BPO or HRT as the referent group, HRT of any type after BPO did not significantly alter the reduction in breast cancer risk associated with BPO (HR = 0.37; 95% CI, 0.14 to 0.96).
Short-term HRT use does not negate the protective effect of BPO on subsequent breast cancer risk in BRCA1/2 mutation carriers.
We compared the outcome of breast-conserving surgery and radiotherapy in BRCA1/2 mutation carriers with breast cancer versus that of matched sporadic controls.
A total of 160 BRCA1/2 mutation ...carriers with breast cancer were matched with 445 controls with sporadic breast cancer. Primary end points were rates of in-breast tumor recurrence (IBTR) and contralateral breast cancers (CBCs). Median follow-up was 7.9 years for mutation carriers and 6.7 years for controls.
There was no significant difference in IBTR overall between carriers and controls; 10- and 15-year estimates were 12% and 24% for carriers and 9% and 17% for controls, respectively (hazard ratio HR, 1.37; P = .19). Multivariate analyses for IBTR found BRCA1/2 mutation status to be an independent predictor of IBTR when carriers who had undergone oophorectomy were removed from analysis (HR, 1.99; P = .04); the incidence of IBTR in carriers who had undergone oophorectomy was not significantly different from that in sporadic controls (P = .37). CBCs were significantly greater in carriers versus controls, with 10- and 15-year estimates of 26% and 39% for carriers and 3% and 7% for controls, respectively (HR, 10.43; P < .0001). Tamoxifen use significantly reduced risk of CBCs in mutation carriers (HR, 0.31; P = .05).
IBTR risk at 10 years is similar in BRCA1/2 carriers treated with breast conservation surgery who undergo oophorectomy versus sporadic controls. As expected, CBCs are significantly increased in carriers. Although the incidence of CBCs was significantly reduced in mutation carriers who received tamoxifen, this rate remained significantly greater than in controls. Additional strategies are needed to reduce contralateral cancers in these high-risk women.
Breast cancer results from genetic and environmental factors leading to the accumulation of mutations in essential genes. Genetic predisposition may have a strong, almost singular effect, as with ...BRCA1 and BRCA2, or may represent the cumulative effects of multiple low-penetrance susceptibility alleles. Here we review high- and low-penetrance breast-cancer-susceptibility alleles and discuss ongoing efforts to identify additional susceptibility genes. Ultimately these discoveries will lead to individualized breast cancer risk assessment and a reduction in breast cancer incidence.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Bilateral prophylactic salpingo-oophorectomy (BPSO) is used widely used to reduce the risk of breast and ovarian cancer in women with
BRCA1 and
BRCA2 mutations. However, the reduction in mortality ...after this surgery is unclear. We aimed to assess whether BPSO improves overall mortality or cancer-specific mortality in
BRCA1 and
BRCA2 mutation carriers.
We identified a prospective cohort of 666 women with disease-associated germline mutations in
BRCA1 or
BRCA2 and no previous cancer diagnosis. In our primary analysis, we compared 155 women who had had BPSO and 271 women matched for age at BPSO who had not had BPSO. In our secondary analysis, we compared 188 women who had had BPSO with 478 women who had not. In both analyses, we compared overall mortality and cancer-specific mortality. All analyses were adjusted for centre, mutation (
BRCA1 vs BRCA2), and birth year.
In the primary analysis, mean follow-up from BPSO to censoring was 3·1 years SD 2·4 in the BPSO group and 2·1 years 2·0 in the non-BPSO group. The hazard ratio (HR) for overall mortality was 0·24 (95% CI 0·08–0·71), for breast-cancer-specific mortality was 0·10 (0·02–0·71), and for ovarian-cancer-specific mortality was 0·05 (0·01–0·46) for women who had BPSO compared with those who had not. In secondary analysis, BPSO was associated with reduced overall mortality (HR 0·28 95% CI 0·10–0·74), but not with breast-cancer-specific mortality (0·15 0·02–1·18 or ovarian-cancer-specific mortality (0·23 0·02–1·87. When regarded as a time-dependent covariate, BPSO was not associated significantly with mortality.
If confirmed, the finding that BPSO improves overall survival and cancer-specific survival in women with BRCA mutations will complement our existing knowledge of cancer-risk reduction associated with BPSO. Together, these data could give information to women who are considering genetic testing.
PDF
