Mutation analysis in the BRCA2 gene in primary breast cancers.

Breast cancer, one of the most common and deleterious of all diseases affecting women, occurs in hereditary and sporadic forms. Hereditary breast cancers are genetically heterogeneous; susceptibility is variously attributable to germline mutations in the BRCA1 (ref. 1), BRCA2 (ref. 2), TP53 (ref. 3) or ataxia telangiectasia (ATM) genes, each of which is considered to be a tumour suppressor. Recently a number of germline mutations in the BRCA2 gene have been identified in families prone to breast cancer. We screened 100 primary breast cancers from Japanese patients for BRCA2 mutations, using PCR-SSCP. We found two germline mutations and one somatic mutation in our patient group. One of the germline mutations was an insertion of an Alu element into exon 22, which resulted in alternative splicing that skipped exon 22. The presence of a 64-bp polyadenylate tract and evidence for an 8-bp target-site duplication of the inserted DNA implied that the retrotransposal insertion of a transcriptionally active Alu element caused this event. Our results indicate that somatic BRCA2 mutations, like somatic mutations in the BRCA1 gene, are very rare in primary breast cancers.

A novel metalloprotease/disintegrin-like gene at 17q21.3 is somatically rearranged in two primary breast cancers.

From chromosomal region 17q21.3, where a tumour suppressor gene(s) for breast and ovarian cancers is thought to be present, we have isolated a novel gene from a cosmid clone that revealed somatic rearrangements in two breast cancers. The gene (MDC) encodes a 524-amino acid metalloprotease-like, disintegrin-like and cysteine-rich protein with sequence similarity to members of the snake-venom metalloprotease/disintegrin family and guinea-pig sperm-surface protein PH-30. These proteins have been implicated in cell-cell or cell-extracellular matrix interactions. Rearrangements in both tumours involve multiple exons and disrupt the coding region of the new MDC.

Experience with intradermal injection and intradermal-plus-deep injection in the radioguided sentinel node biopsy of early breast cancer patients.

AIMS: Methods of administering (99m)Tc-phytate during sentinel node biopsy of early breast cancer patients were compared to improve the sensitivity of the technique. METHODS: Two injection methods, intradermal vs. intradermal-plus-deep injection, were compared in 648 early breast cancer patients. Intradermal injection was done in 323 consecutive patients (325 breasts), and intradermal-plus-deep injection was done in 325 consecutive patients (329 breasts). The following items were compared: (1) The number of axillary nodes detected scintigraphically and removed surgically, and the breast number of micrometastasis to axillary nodes; (2) The number of internal mammary nodes detected scintigraphically and removed surgically; and (3) The sensitivity of axillary SNB. RESULTS: The number of axillary nodes scintigraphically detected was 1.63+/-0.80 (mean+/-SD) in patients given intradermal injection, and was 1.82+/-0.94 in patients given intradermal-plus-deep injection. The number of axillary nodes surgically removed was 1.78+/-0.93 in patients given intradermal injection, and was 1.95+/-0.99 in patients given intradermal-plus-deep injection. The visualization of internal mammary nodes was superior with intradermal-plus-deep injection (5/325 for intradermal, and 51/329 for intradermal-plus-deep). The putative sensitivity was 71/72 (98.6%) for the intradermal-plus-deep method and 56/62 (90.3%) for the intradermal method. The frequency of detection of micrometastasis was 24 in 71 true positive (38.8%) for the intradermal-plus-deep method and 13 in 56 true positive (23.2%) for the intradermal method. CONCLUSIONS: The SNB procedure with the intradermal-plus-deep injection method detected more axillary and internal mammary nodes, more (not statistically significant) micrometastasis and improved the putative sensitivity more than the SNB procedure with the intradermal injection method.

Radioactivity thresholds for sentinel node biopsy in breast cancer.

AIMS: The aim of the present study is to clarify the level of radioactive lymph node should be biopsied after the most radioactive SN is removed. METHODS: SNB using radionuclide was performed in our hospital for 1179 primary breast cancers between April 2000 and October 2005; most (1177/1179) were performed successfully. Our criterion for harvesting SNs is to remove tissue until no radioactive site is present. The level of radioactivity and the order of removal of each lymph node were compared with pathologic results. RESULTS: More than 2 (overall average 1.9) radioactive SNs were biopsied in 686 of 1177 breasts. Cancer positive results were recorded for 142 breasts with multiple SNs. In 142 breasts, 64 showed metastasis to the most radioactive node only, 39 showed metastasis other than the most radioactive node only, and 39 showed the most radioactive node and other radioactive nodes. Moreover, if several other criteria were applied, false-positive cases were increased significantly. CONCLUSIONS: It is necessary to harvest radioactive lymph nodes other than the most radioactive. Moreover, efforts to remove every radioactive lymph node will minimize false-negative results.

Accumulation of genetic alterations and progression of primary breast cancer.

In order to detect common regions of deletion, 219 breast tumors were examined for loss of heterozygosity at several loci on chromosomes 3p, 16q, and 17 by restriction fragment length polymorphism analysis. Allelic deletions of loci on chromosomes 3p, 13q, 16q, and 17, and amplification of the erbB2 oncogene, were analyzed and compared with histopathological and clinical features. Common regions of deletion were detected within chromosomal bands 3p13-14.3, 16q22-23, 17p13 (two separated loci), and 17q21. Concordant losses of alleles on chromosomes 3p, 13q, 16q, 17p, and 17q were observed. A significant association was detected between loss of heterozygosity on chromosomes 17p and 17q and amplification of the erbB2 oncogene (17p, P = 0.000721, by Fisher's exact test; 17q, P less than 0.001, chi 2 = 12.135). Furthermore, tumors showing highly malignant phenotypes had accumulated more genetic changes at the loci studied than those having less malignant phenotypes on the basis of histopathological classification, lymph node metastasis, and tumor size. These results suggested that accumulation of genetic alterations, including loss of function of tumor suppressor genes on chromosomes 3p, 13q, 16q, and 17, and amplification of the erbB2 oncogene, may contribute to tumor development and/or progression in primary breast cancer.

Allelotype of breast cancer: cumulative allele losses promote tumor progression in primary breast cancer.

Allele loss on a specific chromosome has implied the existence of a tumor suppressor gene such as the p53 gene and the RB gene. In order to determine which chromosome(s) carries a tumor suppressor gene(s) that contributes to tumor progression in primary breast cancer, we analyzed the loss of heterozygosity for each autosomal chromosome arm by using 39 restriction fragment length polymorphism markers including 25 variable numbers of tandem repeat probes. In 79 primary breast cancers, we found the frequent loss on the long arm of chromosome 13 (21%), the long arm of chromosome 16 (45%), and the short arm of chromosome 17 (56%). Interestingly, breast cancers in which loss of both chromosomes 13q and 17p was detected showed more malignant histopathological features, and a group of the tumors in which chromosome 16q loss was detected presented with frequent lymph node metastasis. Furthermore, the result of the deletion mapping on chromosome 17p implied the existence of a tumor suppressor gene distal to the p53 gene as well as the p53 gene itself for primary breast cancer. These results suggest that at least 4 tumor suppressor genes exist on chromosomes 13q, 16q, and 17p for primary breast cancer.

Absence of endothelial cells, central necrosis, and fibrosis are associated with aggressive inflammatory breast cancer.

We recently established a new human inflammatory breast cancer (IBC) xenograft (WIBC-9) originating from a patient with IBC. The graft was transplantable in BALB/c nude and severe combined immunodeficient (SCID) mice. WIBC-9 was frequently accompanied by lung metastasis and exhibited erythema of the overlying skin, reflecting its human counterpart. Histological study of the original tumor and WIBC-9 revealed invasive ductal carcinoma with a hypervascular structure of solid nests and marked lymphatic permeation in the overlying dermis. In the central part of the solid nests, absence of endothelial cells, central necrosis, and fibrosis were observed. In vitro, WIBC-9 formed tube-like structures and loops, reflecting its in vivo feature and its human counterpart. WIBC-9 exhibited aneuploidy, ErbB-2 gene amplification, and an absence of estrogen receptor and progesterone receptor, which is consistent with IBC. Comparative studies of WIBC-9, three established non-IBC xenografts, and a human breast cancer cell line (SK-BR3) by reverse transcription-PCR, ELISA, and immunohistochemistry indicated that certain human genes (interleukin 8, vascular epidermal growth factor, basic fibroblast growth factor, angiopoietin 13, Flt-1, Tie-2, and Tie-1) and certain murine genes (integrin alpha(v)beta3, flt-1, tie-2, vascular epidermal growth factor, and CD31) were overexpressed in exposure to tumor cells. The molecular basis and these unique histological features may be associated with aggressive IBC on angiogenic and nonangiogenic pathways.

Detailed deletion mapping of chromosome 17q in ovarian and breast cancers: 2-cM region on 17q21.3 often and commonly deleted in tumors.

Using 11 restriction fragment length polymorphism markers, we examined loss of heterozygosity on the long arm of chromosome 17, where one or more genes responsible for hereditary breast and ovarian cancers may be present, in sporadic forms of 94 ovarian and 246 breast cancers. Loss of heterozygosity was observed in 33 of 84 (39.3%) ovarian and in 88 of 214 (41.1%) breast cancers that were informative with at least one marker. Detailed deletion mapping of chromosome 17q in these cancers identified two distinct, commonly deleted regions. One was located between 17q12 and 17q21.3 and the other between 17q25.1 and 17q25.3. In breast cancers, the proximal commonly deleted region was between two loci defined by markers CI17-701 and CI17-730 at 17q21.3, which are 2.4 cM apart. This segment overlaps the region that includes the putative gene for hereditary breast and ovarian carcinomas. The results suggest that at least two tumor suppressor genes associated with sporadic ovarian and breast cancers are present on chromosome 17q and that one of them may be the same gene that is responsible for the hereditary form.

The human prohibitin gene located on chromosome 17q21 is mutated in sporadic breast cancer.

A gene called "prohibitin" was isolated as a candidate antiproliferating gene in rat liver cells. We have isolated the human homologue of the rat prohibitin gene and mapped it to chromosome 17q12-21 where a gene responsible for hereditary breast cancer was localized. DNA sequence analysis of 2 exons in this gene in 23 sporadic breast cancers, which showed loss of heterozygosity on the long arm of chromosome 17 or developed in patients 35 years old or younger, identified 4 cases of somatic mutation; 2 of these were missense mutations; 1 showed a 2-base deletion resulting in truncation of the gene product due to a frame shift; the other had a C to T transition in an intron adjacent to an intron-exon boundary. These results suggest that this gene may be a tumor suppressor gene and is associated with tumor development and/or progression of at least some breast cancers.

Correlation of loss of alleles on the short arms of chromosomes 11 and 17 with metastasis of primary breast cancer to lymph nodes.

To examine the role of loss of heterozygosity (LOH) during tumor development and/or progression, we looked for correlations between metastasis of breast cancer to a regional lymph node(s) and LOH of chromosomal arms 11p, 13q, 16q, 17p, and 17q, where frequent losses in primary tumors have been detected. No correlation between lymph node metastasis and LOH of chromosomes 13q, 16q, or 17q was observed. However, tumors showing LOH of chromosomes 11p (chi 2 = 10.82, P less than 0.01) and 17p (chi 2 = 6.78, P less than 0.01) revealed a significantly higher incidence of metastasis to a regional lymph node(s) than tumors without LOH on these chromosomal arms. Furthermore, only four of 30 (13%) patients with tumors that retained both 11p and 17p had metastasis to a regional lymph node(s), compared with 24 of 32 (75%) patients with tumors that had lost both 11p and 17p. Analysis of LOH with markers on chromosomes 11p and 17p in a large number of tumors indicated that the peritelomeric region of each of these chromosomal arms contains a tumor suppressor gene that may be associated with tumor progression, particularly metastasis to a regional lymph node(s).

The effect of an old surgical scar on sentinel node mapping in patients with breast cancer: a report of five cases.

AIMS: To study the significance of lymphatic drainage disruption due to a surgical scar in sentinel node mapping (SNM) in breast cancer patients. METHODS: We reviewed patients with stage I breast cancer who had undergone SNM and had an old surgical scar in the ipsilateral breast. RESULTS: Of 534 breast cancer patients who had undergone SNM, five patients had an old scar in the ipsilateral breast. Inter-pectoral nodes, internal nodes, intramammary nodes, and contralateral axillary nodes were identified as sentinel nodes in three cases. In the remaining two cases, no sentinel lymph nodes were identified. CONCLUSIONS: An old surgical scar in the breast may cause lymphatic drainage disruption, resulting in abnormal radioactive colloid uptake during SNM.

Allelic loss at 1p34-36 predicts poor prognosis in node-negative breast cancer.

Allelic losses of specific chromosomal regions in the DNA of tumor cells, which imply loss of tumor suppressor genes normally resident at those loci, may become useful postoperative prognostic indicators for breast cancers that have not yet metastasized to lymph nodes. To examine whether specific allelic losses might correlate with postoperative disease-free survival, we tested tumors from a cohort of 228 node-negative breast cancer patients for allelic losses at 18 microsatellite loci chosen to represent either a known tumor suppressor gene or a region where genetic alterations are frequent in breast tumors. We followed the patients clinically for 5 years or until death (if patient death occurred before completion of 5 years of follow-up). Patients whose tumors had lost an allele at 1p34-36 bore significantly higher risks of postoperative recurrence than those whose tumors retained both alleles of the markers in that region [the 5-year recurrence rate was 15% among patients with losses versus 2% among patients with retention (P = 0.001)]. Multivariate analysis demonstrated that allelic loss at 1p34-36 was an independent postoperative predictor of shorter disease-free survival (hazard ratio, 5.8; P = 0.0117). Thus, allelic losses at 1p34-36 in a tumor might have a potential to serve as a negative prognostic indicator to guide postoperative management of breast cancer patients, especially in the selection of high-risk women who will benefit from adjuvant chemotherapy and endocrine therapy.

Allelic losses of loci at 3p25.1, 8p22, 13q12, 17p13.3, and 22q13 correlate with postoperative recurrence in breast cancer.

We previously defined 18 chromosomal regions in which frequent allelic losses were observed in breast cancers (T. Sato et al., Cancer RES:, 50: 7184-7189, 1990; Y. Harada et al., Cancer (PHILA:), 74: 2281-2286, 1994; I. Ito et al., BR: J. Cancer, 71: 438-441, 1995; K. Tsukamoto et al., Cancer (PHILA:), 78: 1929-1934, 1996; S. Matsumoto et al., Genes Chromosomes Cancer, 20: 268-274, 1997; T. Yokota et al., JPN: J. Cancer RES:, 88: 959-964, 1997; K. Tsukamoto et al., Cancer (PHILA:), 82: 317-322, 1998; A. Iida et al., Genes Chromosomes Cancer, 21: 108-112, 1998; K. Fukino et al., Genes Chromosomes Cancer, 24: 345-350, 1999; T. Yokota et al., Cancer (PHILA:), 85: 447-452, 1999; Y. Utada et al., JPN: J. Cancer RES:, 91: 293-300, 2000). To identify specific allelic losses that might correlate with postoperative recurrence, we examined tumors from a cohort of 504 breast cancer patients, who were followed clinically for 5 years postoperatively, for allelic losses of 18 microsatellite markers. Patients whose tumors had lost an allele at 3p25.1, 8p22, 13q12, 17p13.3, or 22q13 had significantly higher risks of recurrence than those whose tumors retained both alleles at those loci; at 3p25.1, the 5-year recurrence rate was 27% among patients with losses versus 18% with retention (P = 0.0131); at 8p22, 27% versus 14% (P = 0.0129); at 13q12, 28% versus 15% (P = 0.0109); at 17p13.3, 27% versus 20% (P = 0.0482); and at 22q13, 29% versus 20% (P = 0.0477). These data indicate that loss of heterozygosity at any one of these five specific loci is a significant predictor of postoperative recurrence among patients who have undergone surgery for breast cancer. These allelic losses can serve as negative prognostic indicators to guide postoperative management of patients.

Overrepresentation of the EBAG9 gene at 8q23 associated with early-stage breast cancers.

EBAG9, an estrogen-responsive gene located at 8q23 was identified in an effort to clone CpG-binding sites. Its product was later found to be identical to RCAS1, a cancer cell-surface antigen implicated in immune escape. We determined the sequence of the complete cDNA and the genomic structure for EBAG9. EBAG9 gene copy number in 21% (27 of 129) primary breast cancers we examined; EBAG9 mRNA was consistently expressed in cancer cell lines. Detailed physical mapping of the 8q arm, including polymorphic markers for EBAG9 and the CMYC loci, revealed allelic gain of either EBAG9, CMYC, or both, in 45% (58 of 129) of the breast cancers we examined. The EBAG9 gene was increased exclusively in 16 of the 27 tumors showing gain at that locus; the other 11 showed gain of a larger chromosomal region containing both EBAG9 and CMYC. Analysis of subsequent series of 144 primary breast cancers for allelic gain at EBAG9 and CMYC locus showed a similar degree of gain at EBAG9, CMYC, or both. When a total of 273 breast cancers from two series were combined and analyzed for clinicopathological correlation, almost all of the tumors with EBAG9 increased but not those with CMYC. Twenty-eight of 29 were T1/T2 stage carcinomas (<5 cm in diameter), whereas one third (21 of 61) of the tumors in which CMYC was increased but EBAG9 was not, were advanced T3-stage tumors (P = 0.0012). These data suggest that EBAG9 and CMYC gene are independent targets of gain and that overrepresentation of EBAG9 may play a specific role in early stages of breast carcinogenesis.

Identification of a new commonly deleted region within a 2-cM interval of chromosome 11p11 in breast cancers.

Allelic loss has been observed on the short arm of chromosome 11 in a variety of human cancers. We have examined 184 breast cancers for allelic loss anywhere in chromosome 11p, using 15 well-spaced microsatellite markers. Allelic loss was observed in 86 cases (47%) and a new commonly deleted region 2-cM in length was identified at 11p11 between loci D11S986 and D11S1313, in addition to a 12-cM region of a common deletion at 11p15.5. A significant association was found between allelic loss on 11p15.5 and LOH on 11p11 and the loss of progesterone receptors.

Frequent multiplication of chromosome 1q in non-invasive and papillotubular carcinoma of the breast.

Carcinogenesis is considered to be a multistep process that may involve cumulative genetic alterations; one of these mechanisms, gain of chromosomal material, has the potential to activate tumor-promoting genes in breast carcinogenesis. Using 12 polymorphic microsatellite markers on the long arm of chromosome 1 (1q), we examined 130 sporadic breast carcinomas for abnormalities in the copy numbers of these loci in tumor cells using a differential PCR method. We also sought correlations between alterations on 1q and several clinicopathological parameters. At every locus examined, a 2-3-fold increase in copy number of an allele in tumor material was observed in one third of the tumors (46 of 130, 35%), indicating 'multiplication' of 1q. This multiplication involved the entire long arm in majority of those tumors (43 cases, 93%). The multiplication of 1q was observed more frequently in non-invasive ductal and papillotubular histological types than in solid-tubular and scirrhous types (13/25, 52% vs. 27/90, 30%) (P = 0.041). The predominant chromosomal alterations on 1q in breast carcinomas are found to be multiplications rather than losses. The multiplication represents polysomy of the entire region of 1q, and may confer a growth advantage during development and/or progression of non-invasive ductal and papillotubular histologic types of breast carcinomas.

Frequent multiplication of chromosomal region 8q24.1 associated with aggressive histologic types of breast cancers.

Carcinogenesis is considered to be a multi-step process that may involve cumulative genetic alterations. One such alteration, gain of chromosomal material, has the potential for activating genes that promote carcinogenesis in breast tissues. Using 14 polymorphic microsatellite markers on the long arm of chromosome 8 (8q), we examined 142 sporadic breast cancers for abnormalities in the copy-numbers of these loci. At each locus examined, a 2- to 3-fold increase in intensities of bands representing single alleles was observed in 57 (40%) of the tumors, indicating that 'multiplication' of the DNA sequence had occurred on 8q. A 16-cM region on 8q24.1 was commonly multiplied among the tumors with partial multiplications. Multiplication on 8q24.1 was observed more frequently in invasive solid-tubular or scirrhous tumors (48/92, 52%) than in less aggressive histologic types (7/25, 28%, P = 0.031). Thus, multiplication of tumor-promoting gene(s) located on 8q24.1 may play a role in the development and/or progression of a substantial proportion of primary breast cancers, particularly those of the invasive histology.

Loss of heterozygosity at 3p24-p25 as a prognostic factor in breast cancer.

Differences in clinical course and biological characteristics among breast cancers will probably be explained ultimately by variations in the pattern of genetic alterations among the many genes that can play roles in carcinogenesis. Loss of heterozygosity (LOH) of a particular chromosomal region in a tumor, which presumably indicates loss of a growth-regulating 'tumor-suppressor' gene in that region, may represent a useful marker for postoperative prognosis. In earlier work we observed LOH at chromosomal regions 3p14-p21 and/or 3p24-p25 in a large proportion of breast cancers. To examine whether allelic losses in either of those regions might correlate with postoperative survival, we tested tumors from a cohort of 504 breast cancer patients for allelic losses of microsatellite markers in the relevant portions of chromosome 3p. Five years postoperatively, patients whose tumors had undergone LOH at 3p24-p25 were found to have borne significantly higher risks of mortality than women whose tumors retained both alleles at that locus; i.e. the 5-year mortality rate was 22% among patients with losses at 3p24-p25 vs. 9% with retentions of heterozygosity at that locus (P=0.0014). These data indicate that LOH at 3p24-p25 is a significant predictive factor for postoperative survival of patients who have undergone surgery for breast cancer.

Somatic mutation of the PTEN/MMAC1 gene in breast cancers with microsatellite instability.

The extent to which microsatellite instability (MI) contributes to the etiology of breast cancer has not been established in any large-scale studies. We examined 528 samples of tumor DNA from patients with primary breast cancer for MI, using 14 polymorphic CA-repeat markers. The frequency of MI in these tumors was unexpectedly low (10/528, 1.9%). The ten MI+ tumors were analyzed for mutations in five potential target genes that contain simple repeat sequences (TGFBIIR, IGF2R, hMSH6, BAX and PTEN/MMAC1). A somatic insertion of an extra adenine in the (A)6 region at codon 321-323 (exon 8) of the PTEN/MMAC1 gene, leading to a frame-shift, was identified in one tumor. This observation represented the first documented instance of PTEN/MMAC1 alteration in a MI+ primary breast cancer.

The morphologic feature of mucus leakage appearing in low papillary carcinoma of the breast.

This report summarizes the clinicopathologic findings in 11 cases of low papillary carcinoma of the breast accompanied by the morphologic feature of mucus leakage into the mammary stroma. These cases were characterized by two morphologic findings. First, abundant mucus produced by the tumor cells filled the intraductal spaces where neoplastic epithelium formed very low papillary projections, ie, a feature of mucinous-producing low papillary carcinoma in situ. Second, there was expansive leakage of mucus into the mammary stroma occasionally accompanied by a few epithelial cells. All the cases showed a high level of mucus production and contained no elements of invasive ductal carcinoma or ordinary invasive mucinous carcinoma. These cases have no evidence of direct invasion of the mammary stroma by malignant cells. The average age of the 11 patients was 41 years. Foci of microcalcification were seen in some tumors (seven cases; 64%). There were no cases with lymph node metastases. All the patients underwent mastectomy with no adjuvant therapy, and they are currently alive and well.