Active allele loss of the androgen receptor gene contributes to loss of androgen receptor expression in female breast cancers

Given the importance of androgen and androgen receptor (AR) in the control of female breast growth and the potential association with female breast cancer, we evaluated the AR expression in 114 female breast cancers and further analyzed why AR expression was lost. Immunohistochemical analysis revealed that 14.1% (17/114) of the tumors lost the AR expression completely. To unravel the molecular mechanism for AR expression loss, we first analyzed the somatic mutations in exons 2 through 8 of the AR gene by PCR-SSCP, but no mutation was detected. As the CAG repeats within exon 1 are also microsatellite markers, we then analyzed whether allelic loss was present. Interestingly, 11 of the 17 AR-negative tumors were heterozygous and 9 of them showed allelic loss. The lost allele was further demonstrated to be the active one by X-chromosome inactivation analysis. To confirm the immunohistochemical results, Northern and Western blot hybridization was performed and neither AR mRNA nor protein was detected in these AR-negative tumors. Loss of the active AR allele was strongly correlated with the AR expression loss (P = 0.0005). We conclude that AR expression loss is attributed to the active allele loss of AR gene in female breast cancers. Our finding may be also crucial in predicting and influencing the response of breast cancer to endocrine therapy.     

CK2α/CK1α chimeras are sensitive to regulation by the CK2β subunit

The purpose of this study was to analyse the frequency and type of mutations in the coding region of androgen receptor (AR) and to determine the role of polymorphisms in the intron 1 of ERalpha, exon 5 of ERbeta, intron 7 of progesterone, exon 7 of the aromatase (CYP19) and exon 9 of VDR genes in the risk of prostate cancer. PCR-RFLP analysis of all above the genes was on 100 prostate cancer patients and an equal number of matching controls. The study also included PCR-SSCP analyses of exons 2-8 of AR gene. The genotype containing -/- allele of ERalpha gene was statistically significant for the risk of prostate cancer pose (OR, 2.70; 95% CI, 1.08-6.70, P = 0.032) Rr genotype of ERbeta gene also have a higher risk (OR, 1.65; 95% CI, 0.52-5.23) for prostate cancer. The Cys allele of CYP19 gene was also associated with statistically significant increased risk of prostate cancer (OR; 2.28, 95% CI, 1.20-4.35, P = 0.012). tt genotype of codon 352 of VDR gene showed an OR of 0.43 for (95% CI, 0.13-1.39) and an OR for Tt genotype was 0.65 (95% CI, 0.36-1.16). Taken together, the results showed that in North Indian population, ERalpha and CYP19 genes may be playing a role in the risk of prostate cancer.     

Concurrent mutation in exons 1 and 2 of the K-ras oncogene in colorectal cancer

The K-ras gene is frequently mutated in colorectal cancer and has been associated with tumor initiation and progression; approximately 90% of the activating mutations are found in codons 12 and 13 of exon 1 and just under 5% in codon 61 located in exon 2. These mutations determine single aminoacidic substitutions in the GTPase pocket leading to a block of the GTP hydrolytic activity of the K-ras p21 protein, and therefore to its constitutive activation. Point mutations in sites of the K-ras gene, other than codons 12, 13 and 61, and other types of genetic alterations, may occur in a minority of cases, such as in the less frequent cases of double mutations in the K-ras gene. However, all mutations in this gene, even those which occur in non-canonical sites or double mutations, are relevant oncogenic alterations in colorectal cancer and may underlie K-ras pathway hyperactivation. In the present study, we report the case of a patient with colorectal cancer presenting a concurrent point mutation in exons 1 and 2 of the K-ras gene, a GGT to TGT substitution (Glycine to Cysteine) at codon 12, and a GAC to AAC substitution (Aspartic Acid to Asparagine) at codon 57. In addition, we found in the same patient's sample a silent polymorphism at codon 11 (Ala11Ala) of exon 1.     

Novel germline hMSH2 genomic deletion and somatic hMSH2 mutations in a hereditary nonpolyposis colorectal cancer family

Germline and somatic mutations of the hMSH2 gene were determined in a Japanese hereditary nonpolyposis colorectal cancer (HNPCC) family fulfilling the Amsterdam criteria. PCR-SSCP-sequencing of genomic DNA detected a somatic hMSH2 mutation of an A deletion at codon 227-229 in a duodenal carcinoma and a somatic hMSH2 mutation of an A insertion at codon 21 in a gastric carcinoma from affected family members, both carcinomas exhibiting high microsatellite instability. However, no germline hMSH2 mutation was detected by the PCR-SSCP-sequencing method. Genomic DNA was then analyzed by Southern blot hybridization using three hMSH2 cDNA probes (probe A involving exons 1-5, probe B involving exons 4-11 and probe C involving exons 9-16) after digestion by restriction enzymes, EcoRI, HindIII and NsiI. The NsiI digest of DNA from normal tissues of affected members exhibited an aberrant 8.6 kb restriction fragment, in addition to the normal 10.6 kb fragment, when hybridized to probes A and B. This suggested the presence of a heterozygous 2kb genomic deletion encompassing exon 4, 5 or 6. RT-PCR-sequencing revealed that the deleted region encompassed exon 5. This novel genomic deletion of the hMSH2 gene was confirmed to be pathogenic, and the Southern hybridization pattern was applied to the pre-symptomatic diagnosis.     

The detection of mutations induced in vitro in the human p53 gene by hydrogen peroxide with the restriction site mutation (RSM) assay.

We have analysed five mutation hotspots within the p53 gene (codons 175, 213, 248, 249, and 282) for mutations induced by hydrogen peroxide (H(2)O(2)), employing the restriction site mutation (RSM) assay. In addition, four other restriction sites covering non-hotspot codons of exons 5-9 of the p53 gene (codons 126, 153/54, 189 and the 3' splice site of exon 9) were analysed by the RSM assay for H(2)O(2)-induced mutations. Two cell types were concurrently analysed in this study, i.e. primary fibroblast cells and a gastric cancer cell line. Using the RSM assay, H(2)O(2)-induced mutations were only detected in exon 7 of the p53 gene. This was true for both cell types. These mutations were mainly induced in the Msp I restriction site (codon 247/248) and were predominantly GC to AT transitions (71%). Hence these GC to AT mutations were presumably due to H(2)O(2) exposure, possibly implicating the 5OHdC adduct, which is known to induce C to T mutations upon misreplication. Importantly, this study demonstrates that the RSM methodology is capable of detecting rare oxidative mutations within the hotspot codons of the p53 tumour suppressor gene. Hence, this methodology may allow the detection of early p53 mutations in pre-malignant tissues.     

Combined point mutations in codon 12 and 13 of KRAS oncogene in prostate carcinomas

Prostate cancer is a common malignancy that develops by structural mutation(s) and/or other genetic alterations in specific genes.The G to T transversions in codon 12 and C to T transitions in codon 13 of KRAS proto-oncogene are predominant point mutations that occur in about 20% of different cancers in human. In the current study it was aimed to investigate the prevalence and predictive significance of KRAS mutations in patients with prostate carcinomas. In a total of 30 fresh tumoural tissue specimens were investigated in patients with prostate carcinoma. All tumoural specimens were histo-pathologically diagnosed and genotyped for codon 12, 13 KRAS point mutations by reverse hybridisation and direct sequencing methods. KRAS mutations were found in 12 (40%) samples with 29 samples deriving from adenocarcinomas and 1 sample was small cell prostate carcinoma. In 1 (3.44%) sample codon 12 was found to be mutated and in 2 (6.8%) samples codon 13 and in 9 (31%) samples combined codon 12 and 13 were found to be mutated particularly in higher grade of tumoural tissues. Our study, based on representative collection of human prostate tumours, indicates that combined mutations in codons 12 and 13 KRAS are relatively infrequent and most commonly occur in prostate carcinomas.     

Novelty of Axin 2 and lack of Axin 1 gene mutation in colorectal cancer: a study in Kashmiri population

Colorectal cancer is (CRC) one of the leading causes of mortality and morbidity. Various genetic factors have been reported to be involved in the development of colorectal cancers including Axin gene. Axin, a major scaffold protein, plays an important role in various bio signaling pathways. We aim to study mutational pattern of Axin gene in colorectal cancer patients of Kashmiri population. The paired tumor and adjacent normal tissue specimens of 50 consecutive patients with CRC were used in our study. The DNA preparations were evaluated for the occurrence of Axin 1 and Axin 2 gene mutations by direct DNA sequencing. We analyzed exon 1a, 1b, 1c, 2, 4, 6, and 10 of Axin 1 and exon 7 of Axin 2. In this study, we found a novel mutation of G>T (GCT>TCT) transversion in exon 7 of Axin 2 gene at codon G695T (p.alanine >?serine) at a frequency of 6% (3/50). In the same exon of Axin 2 gene a single nucleotide polymorphism (SNP) was detected in codon L688L (CCT>CTT) at a frequency of 36% (18/50). In exon 1c of Axin 1 a SNP was detected at codon D726D (GAT>GAC) at a frequency of 62.5% (31/50). Both the SNPs were synonymous hence do not lead to change of amino acid. Although Axin 1 and Axin 2 gene mutations have been found to be involved in the development of colorectal cancers, it seems to be a relatively rare event in Kashmiri population. However, an interesting finding of this study is the novelty of Axin 2 gene mutations which may be a predisposing factor in ethnic Kashmiri population to CRC.     

Prevalence and penetrance of germline BRCA1 and BRCA2 mutations in a population series of 649 women with ovarian cancer

A population-based series of 649 unselected incident cases of ovarian cancer diagnosed in Ontario, Canada, during 1995-96 was screened for germline mutations in BRCA1 and BRCA2. We specifically tested for 11 of the most commonly reported mutations in the two genes. Then, cases were assessed with the protein-truncation test (PTT) for exon 11 of BRCA1, with denaturing gradient gel electrophoresis for the remainder of BRCA1, and with PTT for exons 10 and 11 of BRCA2. No mutations were found in all 134 women with tumors of borderline histology. Among the 515 women with invasive cancers, we identified 60 mutations, 39 in BRCA1 and 21 in BRCA2. The total mutation frequency among women with invasive cancers, 11.7% (95% confidence interval [95%CI] 9.2%-14.8%), is higher than previous estimates. Hereditary ovarian cancers diagnosed at age <50 years were mostly (83%) due to BRCA1, whereas the majority (60%) of those diagnosed at age >60 years were due to BRCA2. Mutations were found in 19% of women reporting first-degree relatives with breast or ovarian cancer and in 6.5% of women with no affected first-degree relatives. Risks of ovarian, breast, and stomach cancers and leukemias/lymphomas were increased nine-, five-, six- and threefold, respectively, among first-degree relatives of cases carrying BRCA1 mutations, compared with relatives of noncarriers, and risk of colorectal cancer was increased threefold for relatives of cases carrying BRCA2 mutations. For carriers of BRCA1 mutations, the estimated penetrance by age 80 years was 36% for ovarian cancer and 68% for breast cancer. In breast-cancer risk for first-degree relatives, there was a strong trend according to mutation location along the coding sequence of BRCA1, with little evidence of increased risk for mutations in the 5' fifth, but 8.8-fold increased risk for mutations in the 3' fifth (95%CI 3.6-22.0), corresponding to a carrier penetrance of essentially 100%. Ovarian, colorectal, stomach, pancreatic, and prostate cancer occurred among first-degree relatives of carriers of BRCA2 mutations only when mutations were in the ovarian cancer-cluster region (OCCR) of exon 11, whereas an excess of breast cancer was seen when mutations were outside the OCCR. For cancers of all sites combined, the estimated penetrance of BRCA2 mutations was greater for males than for females, 53% versus 38%. Past studies may have underestimated the contribution of BRCA2 to ovarian cancer, because mutations in this gene cause predominantly late-onset cancer, and previous work has focused more on early-onset disease. If confirmed in future studies, the trend in breast-cancer penetrance, according to mutation location along the BRCA1 coding sequence, may have significant impact on treatment decisions for carriers of BRCA1-mutations. As well, BRCA2 mutations may prove to be a greater cause of cancer in male carriers than previously has been thought.     

Three novel germline mutations in MLH1 and MSH2 in families with Lynch syndrome living on Jeju island, Korea

Hereditary non-polyposis colorectal cancer (HNPCC) is an autosomal dominant syndrome characterized by predisposition to early-onset cancers. HNPCC is caused by heterozygous loss-of-function mutations within the mismatch repair genes MLH1, MSH2, MSH6, PMS1, and PMS2. We genotyped the MLH1 and MSH2 genes in patients suffering from Lynch syndrome and in 11 unrelated patients who were diagnosed with colorectal cancer and had subsequently undergone surgery. Five Lynch syndrome patients carried germline mutations in MLH1 or MSH2. Two of these were identified as known mutations in MLH1: deletion of exon 10 and a point mutation (V384D). The remaining three patients exhibited novel mutations: a duplication (937_942dupGAAGTT) in MLH1; deletion of exons 8, 9, and 10; and a point mutation in MLH1 (F396I) combined with multiple missense mutations in MSH2 (D295G, K808E, Q855P, and I884T). The findings underline the importance of efficient pre-screening of conspicuous cases.     

Predisposition for cysteine substitutions in the immunoglobulin-like chain of FGFR2 in Crouzon syndrome

Four cases of Crouzon syndrome, one familial and three sporadic, were investigated for mutations in exon B of the fibroblast growth factor receptor 2 (FGFR2) gene. In the familial case, a mutation was found at codon 340 that exchanged tyrosine for histidine. Mutations at codon 342, detected in the three sporadic cases, replaced a cysteine by another amino acid. While three of the mutations have been described before, the fourth mutation, a CG transversion at codon 342 in one of the sporadic cases, has not been recognized previously. Compilation of all exon B mutations in Crouzon syndrome described to date revealed that 6 of the 8 sporadic and 2 of the 9 familial cases have mutations in codon 342. These mutations caused the substitution of cysteine for another amino acid. Given that a mutation in codon 342 was found in 8 out of 17 cases and that in 9 cases the mutation occurred at five additional positions, codon 342 of exon B of the FGFR2 gene may be predisposed to mutations in Crouzon syndrome.     

Prevalence of c-KIT Mutations in Gonadoblastoma and Dysgerminomas of Patients with Disorders of Sex Development (DSD) and Ovarian Dysgerminomas

Activating c-KIT mutations (exons 11 and 17) are found in 10-40% of testicular seminomas, the majority being missense point mutations (codon 816). Malignant ovarian dysgerminomas represent ～3% of all ovarian cancers in Western countries, resembling testicular seminomas, regarding chromosomal aberrations and c-KIT mutations. DSD patients with specific Y-sequences have an increased risk for Type II Germ Cell Tumor/Cancer, with gonadoblastoma as precursor progressing to dysgerminoma. Here we present analysis of c-KIT exon 8, 9, 11, 13 and 17, and PDGFRA exon 12, 14 and 18 by conventional sequencing together with mutational analysis of c-KIT codon 816 by a sensitive and specific LightCycler melting curve analysis, confirmed by sequencing. The results are combined with data on TSPY and OCT3/4 expression in a series of 16 DSD patients presenting with gonadoblastoma and dysgerminoma and 15 patients presenting pure ovarian dysgerminomas without DSD. c-KIT codon 816 mutations were detected in five out of the total of 31 cases (all found in pure ovarian dysgerminomas). A synonymous SNP (rs 5578615) was detected in two patients, one DSD patient (with bilateral disease) and one patient with dysgerminoma. Next to these, three codon N822K mutations were detected in the group of 15 pure ovarian dysgerminomas. In total activating c-KIT mutations were found in 53% of ovarian dysgerminomas without DSD. In the group of 16 DSD cases a N505I and D820E mutation was found in a single tumor of a patient with gonadoblastoma and dysgerminoma. No PDGFRA mutations were found. Positive OCT3/4 staining was present in all gonadoblastomas and dysgerminomas investigated, TSPY expression was only seen in the gonadoblastoma/dysgerminoma lesions of the 16 DSD patients. This data supports the existence of two distinct but parallel pathways in the development of dysgerminoma, in which mutational status of c-KIT might parallel the presence of TSPY.     

Most human carcinomas of the exocrine pancreas contain mutant c-K-ras genes

Using in vitro gene amplification by the polymerase chain reaction (PCR) and mutation detection by the RNAase A mismatch cleavage method, we have examined c-K-ras genes in human pancreatic carcinomas. We used frozen tumor specimens and single 5 micron sections from formalin-fixed, paraffin-embedded tumor tissue surgically removed or obtained at autopsy. Twenty-one out of 22 carcinomas of the exocrine pancreas contained c-K-ras genes with mutations at codon 12. In seven cases tested, the mutation was present in both primary tumors and their corresponding metastases. No mutations were detected in normal tissue from the same cancer patients or in five gall bladder carcinomas. We conclude from these results that c-K-ras somatic mutational activation is a critical event in the oncogenesis of most, if not all, human cancers of the exocrine pancreas.     

BRCA2 in American families with four or more cases of breast or ovarian cancer: recurrent and novel mutations, variable expression, penetrance, and the possibility of families whose cancer is not attributable to BRCA1 or BRCA2.

In order to evaluate the role of inherited BRCA2 mutations in American families--particularly the appearance in America of European founder mutations--the BRCA2 coding sequence, 5' UTR, and 3' UTR were screened in 22 Caucasian American kindreds with four or more cases of breast or ovarian cancer. Six mutations were found that cause a premature-termination codon; four of them have been reported elsewhere, and two are novel. In the four families with previously seen mutations, the distinct lineages at high risk of cancer were of Dutch, German, Irish, and Ashkenazi Jewish ancestry; mutations in Europe reflect these ancestries. The families with novel mutations were Puerto Rican Hispanic (exon 9 deletion 995delCAAAT) and Ashkenazi Jewish (exon 11 deletion 6425delTT). Among female BRCA2-mutation carriers, risks of breast cancer were 32% by age 50 years, 67% by age 70 years, and 80% by age 90 years, yielding a lifetime risk similar to that for BRCA1 but an older distribution of ages at onset. BRCA2 families also included multiple cases of cancers of the male breast (six cases), ovary (three cases), fallopian tube (two cases), pancreas (three cases), bladder (two cases), and prostate (two cases). Among 17 Ashkenazi Jewish families with four or more breast or ovarian cancers, 9 families (including 3 with ovarian cancer and 1 with male breast cancer) carried none of the three ancient mutations in BRCA1 or BRCA2. To date, both BRCA2 and BRCA1 have been screened by SSCA, supplemented by the protein-truncation test, in 48 families with four or more breast or ovarian cancers. Mutations have been detected in BRCA1 in 33 families, in BRCA2 in 6 families, and in neither gene in 9 families, suggesting both the probable cryptic nature of some mutations and the likelihood of at least one other BRCA gene.     

Multiple mutations of the p53 gene in human mammary carcinoma

Alteration of the p53 tumor suppressor gene is the most common genetic abnormality in human cancer. In breast cancer, depending on the stage of disease and method of detection, mutation rates of 25-60% have been observed. Multiple mutations of p53 gene in the same tumor however, are rarely reported. In this study we explored the frequency of multiple mutations of p53 gene in mammary carcinoma in a cohort of south Florida patients. Three hundred eighty-four cases of primary breast cancer diagnosed between 1984 and 1986 at the University of Miami, Jackson Medical Center were subjects of this study. Sequence analysis of exons 5 through 8 of p53 was performed on cloned PCR-amplified DNA of formalin-fixed, paraffin-embedded tumors. Two hundred thirty-four of 384 breast cancers (61%) had p53 mutation. Of those, 36 tumors showed more than one mutation; 31 tumors had two mutations, three showed three, one tumor had five mutations, and one case carried six mutations. The majority of mutations were missense (43) followed by silent (35); and most occurred within a single exon. Our study suggests that multiple mutations of p53 suppressor gene in breast cancer are more common than currently believed.     

Mutation analysis of the RET proto-oncogene in Dutch families with MEN 2A, MEN 2B and FMTC: two novel mutations and one de novo mutation for MEN 2A

Hereditary C-cell carcinoma is encountered in multiple endocrine neoplasia type 2A (MEN 2A), MEN 2B, and familial medullary thyroid carcinoma (FMTC). Mutations of the RET proto-oncogene are associated with all three diseases. To obtain an insight into the molecular heterogeneity of MEN 2 syndromes and FMTC in the Netherlands, probands of 20 MEN 2A families, two FMTC families, and seven MEN 2B families were analyzed by the polymerase chain reaction (PCR), DNA sequencing, and restriction enzyme digestion for abnormalities in the RET proto-oncogene. RET mutations were found in all cases. All MEN 2A families had a mutation involving one of five cysteine codons in exons 10 and 11 of RET. Two novel dinucleotide mutations and a de novo mutation were found. Both FMTC families had a mutation of the Cys at codon 618. All MEN 2B probands carried a Met to Thr mutation in exon 16. All mutations could be confirmed by restriction enzyme digestion of PCR amplicons. Identification of the RET mutation in the Dutch population with hereditary C-cell carcinoma facilitates genetic testing for families or individuals at risk for MEN 2A, FMTC, and MEN 2B.     

Structure of human holocarboxylase synthetase gene and mutation spectrum of holocarboxylase synthetase deficiency

Holocarboxylase synthetase (HLCS) is an enzyme that catalyzes the incorporation of biotin into apo-carboxylases, and its deficiency causes biotin-responsive multiple carboxylase deficiency. The reported sequences of cDNA for human HLCS from liver, lymphocyte, and KG-1 myeloid cell lines differ at their 5' regions. To elucidate variations of the human HLCS mRNA and longer 5' cDNA ends, we performed screening of the human liver cDNA library and rapid amplification of the cDNA ends (RACE). Our results suggest the existence of three types of HLCS mRNA that start at different exons. The first type starts at exon 1, and the second type starts at exon 3, and both are found in various human tissues. The third type, corresponding to the cDNA from the KG-1 cell, starts at exon 2 of the HLCS gene. Various splicing patterns from exons 3-6 were also observed. None of the variations of cDNA found created a new initiation codon. Mutation screening from exons 6-14, therefore, was sufficient to detect amino acid changes in HLCS in patients. Our direct sequencing strategy for screening mutations in the HLCS gene revealed mutations in five Japanese patients and seven non-Japanese patients. Our analyses involving 12 Japanese and 13 non-Japanese patients and studies by others indicate that (1) there is no panethnically prevalent mutation; (2) the Arg508Trp, Gly581Ser, and Val550Met mutations are found in both Japanese and non-Japanese populations; (3) the IVS10+5G-->A mutation is predominant and probably a founder mutation in European patients; (4) the 655-656insA, Leu237Pro, and 780delG mutations are unique in Japanese patients; (5) the spectrum of the mutations in the HLCS gene may vary substantially among different ethnic groups.     

A missense mutation (Trp86----Arg) in exon 3 of the lipoprotein lipase gene: a cause of familial chylomicronemia.

We have investigated a patient of English ancestry with familial chylomicronemia caused by lipoprotein lipase (LPL) deficiency. DNA sequence analysis of all exons and intron-exon boundaries of the LPL gene identified two single-base mutations, a T----C transition for codon 86 (TGG) at nucleotide 511, resulting in a Trp86----Arg substitution, and a C----T transition at nucleotide 571, involving the codon CAG encoding Gln106 and producing Gln106----Stop, a mutation described by Emi et al. The functional significance of the two mutations was confirmed by in vitro expression and enzyme activity assays of the mutant LPL. Linkage analysis established that the patient is a compound heterozygote for the two mutations. The Trp86----Arg mutation in exon 3 is the first natural mutation identified outside exons 4-6, which encompass the catalytic triad residues.