Systemic stromal effects of estrogen promote the growth of estrogen receptor-negative cancers

Numerous hormonal factors contribute to the lifetime risk of breast cancer development. These include inherited genetic mutations, age of menarche, age of menopause, and parity. Inexplicably, there is evidence indicating that ovariectomy prevents the formation of both estrogen receptor (ER)-positive and ER-negative breast cancers, suggesting that ER-negative breast cancers are dependent on ovarian hormones for their formation. To examine the mechanism(s) by which this may be occurring, we investigated the hypothesis that steroid hormones promote the outgrowth of ER-negative cancers by influencing host cell types distinct from the mammary epithelial cells. We used a novel xenograft mouse model of parturition-induced breast carcinoma formation, in which the tumors that arise following pregnancy lack the expression of nuclear hormone receptors, thereby recapitulating many clinical cases of this disease. Despite lacking ER expression, the tumors arising following pregnancy in this model require circulating estrogens for their formation. Moreover, increasing the levels of circulating estrogens sufficed to promote the formation and progression of ER-negative cancers, which was accompanied by a systemic increase in host angiogenesis and was attendant with the recruitment of bone marrow-derived stromal cells. Furthermore, bone marrow cells from estrogen-treated mice were sufficient to promote tumor growth. These results reveal a novel mechanism by which estrogens promote the growth of ER-negative cancers.

Akt1 ablation inhibits, whereas Akt2 ablation accelerates, the development of mammary adenocarcinomas in mouse mammary tumor virus (MMTV)-ErbB2/neu and MMTV-polyoma middle T transgenic mice

Ample evidence to date links the phosphatidylinositol 3-kinase-regulated protein kinase Akt with the induction and progression of human cancer, including breast cancer. However, there are three Akt isoforms with limited information about their specificity during oncogenesis. This study addresses the role of the three isoforms in polyoma middle T (PyMT) and ErbB2/Neu-driven mammary adenocarcinomas in mice. The effects of ablation of Akt1, Akt2, and Akt3 on the induction and the biology of these tumors were dramatically different, with ablation of Akt1 inhibiting, ablation of Akt2 accelerating, and ablation of Akt3 having a small, not statistically significant, inhibitory effect on tumor induction by both transgenes. Whereas PyMT-induced tumors are all invasive, Akt1(-/-)Neu-induced tumors are more invasive than Akt2(-/-)Neu-induced tumors. Invasiveness, however, does not always correlate with metastasis. Ablation of individual Akt isoforms does not affect the development of the mammary gland during puberty or the expression of the transgenes. Akt ablation, therefore, influences tumor induction by modulating transgene-induced oncogenic signaling. Immunostaining for Ki-67 and cyclin D1 and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assays on tissue sections revealed that the delay of tumor induction in Akt1 knockout mice is due to the inhibitory effects of Akt1 ablation on cell proliferation and survival. Given that these animal models exhibit significant similarities to human breast cancer, the results of the present study may have significant translational implications because they may influence how Akt inhibitors will be used in the treatment of human cancer.

A mouse model of human breast cancer metastasis to human bone

Currently, an in vivo model of human breast cancer metastasizing from the orthotopic site to bone does not exist, making it difficult to study the many steps of skeletal metastasis. Moreover, models used to identify the mechanisms by which breast cancer metastasizes to bone are limited to intracardiac injection, which seeds the cancer cells directly into the circulation, thus bypassing the early steps in the metastatic process. Such models do not reflect the full process of metastasis occurring in patients. We have developed an animal model of breast cancer metastasis in which the breast cancer cells and the bone target of osteotropic metastasis are both of human origin. The engrafted human bone is functional, based on finding human IgG in the mouse bloodstream, human B cells in the mouse spleen, and normal bone histology. Furthermore, orthotopic injection of a specific human breast cancer cell line, SUM1315 (derived from a metastatic nodule in a patient), later resulted in both bone and lung metastases. In the case of bone, metastasis was to the human implant and not the mouse skeleton, indicating a species-specific osteotropism. This model replicates the events observed in patients with breast cancer skeletal metastases and serves as a useful and relevant model for studying the disease.

The melanocyte differentiation program predisposes to metastasis after neoplastic transformation

The aggressive clinical behavior of melanoma suggests that the developmental origins of melanocytes in the neural crest might be relevant to their metastatic propensity. Here we show that primary human melanocytes, transformed using a specific set of introduced genes, form melanomas that frequently metastasize to multiple secondary sites, whereas human fibroblasts and epithelial cells transformed using an identical set of genes generate primary tumors that rarely do so. Notably, these melanomas have a metastasis spectrum similar to that observed in humans with melanoma. These observations indicate that part of the metastatic proclivity of melanoma is attributable to lineage-specific factors expressed in melanocytes and not in other cell types analyzed. Analysis of microarray data from human nevi shows that the expression pattern of Slug, a master regulator of neural crest cell specification and migration, correlates with those of other genes that are important for neural crest cell migrations during development. Moreover, Slug is required for the metastasis of the transformed melanoma cells. These findings indicate that melanocyte-specific factors present before neoplastic transformation can have a pivotal role in governing melanoma progression.

Loss of Heterozygosity Occurs via Mitotic Recombination in Trp53+/− Mice and Associates with Mammary Tumor Susceptibility of the BALB/c Strain

Loss of heterozygosity (LOH) occurs commonly in cancers causing disruption of tumor suppressor genes and promoting tumor progression. BALB/c-Trp53(+/-) mice are a model of Li-Fraumeni syndrome, exhibiting a high frequency of mammary tumors and other tumor types seen in patients. However, the frequency of mammary tumors and LOH differs among strains of Trp53(+/-) mice, with mammary tumors occurring only on a BALB/c genetic background and showing a high frequency of LOH, whereas Trp53(+/-) mice on a 129/Sv or (C57BL/6 x 129/Sv) mixed background have a very low frequency of mammary tumors and show LOH for Trp53 in only approximately 50% of tumors. We have performed studies on tumors from Trp53(+/-) mice of several genetic backgrounds to examine the mechanism of LOH in BALB/c-Trp53(+/-) mammary tumors. By Southern blotting, 96% (24 of 25) of BALB/c-Trp53(+/-) mammary tumors displayed LOH for Trp53. Karyotype analysis indicated that cells lacking one copy of chromosome 11 were present in all five mammary tumors analyzed but were not always the dominant population. Comparative genomic hybridization analysis of these five tumors indicated either loss or retention of the entire chromosome 11. Thus chromosome loss or deletions within chromosome 11 do not account for the LOH observed by Southern blotting. Simple sequence length polymorphism analysis of (C57BL/6 x BALB/c) F1-Trp53(+/-) mammary tumors showed that LOH occurred over multiple loci and that a combination of maternal and paternal alleles were retained, indicating that mitotic recombination is the most likely mechanism of LOH. Nonmammary tumors of BALB/c mice also showed a high frequency of LOH (22 of 26, 85%) indicating it was not a mammary tumor specific phenomenon but rather a feature of the BALB/c strain. In (C57BL/6 x BALB/c) F1-Trp53(+/-) mice LOH was observed in 93% (13 of 14) of tumors, indicating that the high frequency of LOH was a dominant genetic trait. Thus the high frequency of LOH for Trp53 in BALB/c-Trp53(+/-) mammary tumors occurs via mitotic recombination and is a dominant genetic trait that associates with the occurrence of mammary tumors in (C57BL/6 x BALB/c) F1-Trp53(+/-) mice. These results further implicate double-strand DNA break repair machinery as important contributors to mammary tumorigenesis.

Loss of expression of the putative tumor suppressor NES1 gene in biopsy-proven ductal carcinoma in situ predicts for invasive carcinoma at definitive surgery

PURPOSE

The loss of expression of NES1, a novel putative tumor suppressor gene, is an early marker of breast tumorigenesis. NES1 is expressed in normal breast tissue and ductal hyperplasia but is absent or markedly diminished in invasive cancer. In cases of ductal carcinoma in situ (DCIS), NES1 expression has been shown previously to be present in approximately 50% of specimens. This study examined the expression level of NES1 in diagnostic biopsy samples found to contain pure DCIS. These data were then correlated with the pathologic findings found at definitive local surgery.

METHODS AND MATERIALS

Twenty-nine cases with initial biopsy showing DCIS without invasive carcinoma followed by subsequent reexcision were discovered and archived. Formalin-fixed tissue specimens were obtained for analysis. Each biopsy specimen was subjected to hematoxylin-eosin staining and reviewed by two pathologists to confirm the diagnosis of pure DCIS. NES1 cDNA (1069 bp), including 238 bp of 5' and 3' untranslated region and the entire protein-coding region, was cloned into a vector. To generate the antisense and sense RNA probes, the plasmid was linearized and the transcription reaction was carried out with polymerases T7 and T3, respectively. The detection of in situ hybridization probes was performed using an mRNAlocator-Biotin Kit. Staining was characterized as negative (0/1+) or positive (2+/3+). Subsequent to an initial biopsy diagnosis of DCIS, all cases had a definitive surgical procedure. Detailed sectioning of the resultant tissue was performed and subjected to hematoxylin-eosin staining to determine the presence or absence of invasive carcinoma.

RESULTS

The initial diagnostic biopsy specimens showed that 17 of 17 high-grade, 3 of 7 intermediate-grade, and 3 of 5 low-grade DCIS specimens were negative for NES1 expression. Of the 6 cases of DCIS found to be positive for NES1 expression, none (0%) were subsequently found to have invasive carcinoma at definitive surgery. In contrast, the loss of NES1 expression in the initial diagnostic biopsy was associated with a 40% incidence of invasive carcinoma at definitive surgery. Additional stratification by nuclear grade showed invasive carcinoma in 5 (83%) of 6 NES1-negative, low- to intermediate-grade DCIS (p </=0.01) and 4 (24%) of 17 NES1-negative, high-grade DCIS (p </=0.05).

CONCLUSION

These results show that a lack of NES1 expression in DCIS identified at the diagnostic biopsy predicts for a high risk of invasive cancer in the definitive surgical specimen. The predictive value of NES1 expression appears to be particularly relevant for low- and intermediate-grade DCIS.

BALB/c alleles for Prkdc and Cdkn2a interact to modify tumor susceptibility in Trp53+/- mice

In mice heterozygous for p53 (Trp53(+/-)), the incidence of mammary tumors varies among strains, with C57BL/6 being resistant and BALB/c being susceptible. Mammary tumor phenotypes were examined in female Trp53(+/-) F1 mice (C57BL/6 x BALB/c;n = 19) and N2 backcross mice [(C57BL/6 x BALB/c) x BALB/c] (n = 224). Susceptibility to mammary tumors segregated as a dominant phenotype in F1 females, but a higher frequency and shorter latency in N2 mice indicated a contribution from recessive-acting modifiers. Segregation of the hypomorphic BALB/c alleles for DNA-dependent protein kinase catalytic subunit (Prkdc) and p16(INK4A) (Cdkn2a) was analyzed in the N2 mice. The time to first tumor (considering all tumor types) was significantly different among the four genotype combinations (P = 0.01). Cdkn2a had a strong effect (P = 0.008) but was restricted to Prkdc(B/B) mice (P = 0.001), indicating a strong interaction between the loci. Differences in mammary tumor occurrence among genotypes for Prkdc and Cdkn2a in N2 mice were not statistically significant. This study indicates that BALB/c Prkdc and Cdkn2a alleles do modify tumor incidence in Trp53(+/-) mice and highlights the complexity of gene interaction effects in determining cancer phenotypes but discounts these alleles as major recessive loci contributing to spontaneous mammary tumor susceptibility.

Epithelial cell cycling predicts p53 responsiveness to γ-irradiation during post-natal mammary gland development

The tumor suppressor gene, TP53, plays a major role in surveillance and repair of radiation-induced DNA damage. In multiple cell types, including mammary epithelial cells, abrogation of p53 (encoded by Trp53) function is associated with increased tumorigenesis. We examined γ-irradiated BALB/c-Trp53+/+ and -Trp53–/– female mice at five stages of post-natal mammary gland development to determine whether radiation-induced p53 activity is developmentally regulated. Our results show that p53-mediated responses are attenuated in glands from irradiated virgin and lactating mice, as measured by induction of p21/WAF1 (encoded by Cdkn1a) and apoptosis, while irradiated early- and mid-pregnancy glands exhibit robust p53 activity. There is a strong correlation between p53-mediated apoptosis and the degree of cellular proliferation, independent of the level of differentiation. In vivo, proliferation is intimately influenced by steroid hormones. To determine whether steroid hormones directly modulate p53 activity, whole organ cultures of mammary glands were induced to proliferate using estrogen plus progesterone or epidermal growth factor plus transforming growth factor-α and p53 responses to γ-irradiation were measured. Regardless of mitogens used, proliferating mammary epithelial cells show comparable p53 responses to γ-irradiation, including expression of nuclear p53 and p21/WAF1 and increased levels of apoptosis, compared to non-proliferating irradiated control cultures. Our study suggests that differences in radiation-induced p53 activity during post-natal mammary gland development are influenced by the proliferative state of the gland, and may be mediated indirectly by the mitogenic actions of steroid hormones in vivo.

Analysis of normal epithelial cell specific-1 (NES1)/kallikrein 10 mRNA expression by in situ hybridization, a novel marker for breast cancer

PURPOSE

Normal epithelial cell specific-1 (NES1)/kallikrein 10 gene is expressed in normal mammary and prostate epithelial cells, but the expression of NES1 mRNA and protein is markedly reduced in established breast and prostate cancer cell lines although the NES1 gene is intact. Here, we wished to assess whether NES1 expression is down-regulated in primary breast cancers.

EXPERIMENTAL DESIGN

We developed and used an in situ hybridization technique with an antisense NES1 probe to detect NES1 mRNA in sections of normal breast specimens, typical and atypical ductal hyperplasia, ductal carcinoma in situ, and infiltrating ductal carcinoma.

RESULTS

All of the 30 normal breast specimens showed high NES1 expression. Notably, 18 (75%) of 24 typical and atypical breast hyperplasia specimens showed high NES1 expression, with weak-to-moderate expression in 6 (25%). Significantly, 13 (46%) of 28 ductal carcinoma in situ specimens lacked NES1 expression, and the remaining 15 (54%) showed weak-to-moderate expression. Finally, 29 of 30 (97%) infiltrating ductal carcinoma grades I-III samples lacked NES1 mRNA, with weak expression in the remaining one sample.

CONCLUSIONS

Our results demonstrate that NES1 mRNA is expressed in normal breast tissue and benign lesions, with loss of NES1 expression during tumor progression. We suggest that NES1 expression may serve as a molecular tool in the study of breast cancer progression. Studies with larger series of specimens should help assess whether NES1 expression can be a diagnostic and/or prognostic marker in breast and other cancers.

Development of spontaneous mammary tumors in BALB/c p53 heterozygous mice. A model for Li-Fraumeni syndrome

Breast cancer is the most frequent tumor type among women in the United States and in individuals with Li-Fraumeni syndrome. The p53 tumor suppressor gene is altered in a large proportion of both spontaneous breast malignancies and Li-Fraumeni breast cancers. This suggests that loss of p53 can accelerate breast tumorigenesis, yet p53-deficient mice rarely develop mammary tumors. To evaluate the effect of p53 loss on mammary tumor formation, the p53(null) allele was back-crossed onto the BALB/c genetic background. Median survival was 15.4 weeks for BALB/c-p53(-/-) mice compared to 54 weeks for BALB/c-p53(+/-) mice. Sarcomas and lymphomas were the most frequent tumor types in BALB/c-p53(-/-) mice, whereas 55% of the female BALB/c-p53(+/-) mice developed mammary carcinomas. The mammary tumors were highly aneuploid, frequently lost the remaining wild-type p53 allele, but rarely lost BRCA1. Although mammary tumors were rarely detected in BALB/c-p53(-/-) female mice, when glands from BALB/c-p53(-/-) mice were transplanted into wild-type BALB/c hosts, 75% developed mammary tumors. The high rate of mammary tumor development in the BALB/c background, but not C57Bl/6 or 129/Sv, suggests a genetic predisposition toward mammary tumorigenesis. Therefore, the BALB/c-p53(+/-) mice provide a unique model for the study of breast cancer in Li-Fraumeni syndrome. These results demonstrate the critical role that the p53 tumor suppressor gene plays in preventing tumorigenesis in the mammary gland.

Cytoplasmic sequestration and functional repression of p53 in the mammary epithelium is reversed by hormonal treatment

Proper function of the p53 tumor suppressor gene is critical for inhibiting tumor development in a broad spectrum of tissues. Although the mammary gland is highly susceptible to tumor formation, the functional status of p53 in the normal tissue had not been investigated. Therefore, expression, localization, and activity of p53 were examined in normal mammary tissues. High levels of p53 protein were found expressed in the cytoplasm of the ductal epithelium of the quiescent mammary gland. Ionizing radiation failed to recruit p53 to the nucleus, and p53-dependent responses were minimal. However, transient hormonal stimulation resulted in nuclear accumulation of p53, an induction of p21/WAF1, and a 5-fold increase in apoptosis after ionizing radiation. Therefore, the functional state of wild-type p53 in the mammary epithelium can be regulated by hormonal stimuli.

Expression of MDM2 during mammary tumorigenesis

The MDM2 oncoprotein encodes a 90 kDa nuclear phosphoprotein capable of abrogating the growth suppressive functions of p53 and pRb tumor suppressor proteins by direct interaction. Alternative splicing of MDM2 protein coding sequences has been documented during tumor progression in human ovarian and bladder carcinomas. The aim of this study was to determine whether alternative splicing of MDM2 occurs during breast tumorigenesis in mice and humans and whether protein coding sequences were affected. Specimens representing normal and malignant breast tissues from the murine D2 mammary tumor model system and human breast carcinomas were examined. Three distinct mdm2 mRNA transcripts of 3.3, 1.6 and 1.5 kb were detected in normal and malignant murine mammary tissues by Northern blot analysis using a full-length mdm2 cDNA probe. Additional Northern blot analysis using a probe derived from exon 12 of murine mdm2 demonstrated that the 1.5 and 1.6 kb transcripts lack sequences encoding the C-terminus of the protein. No evidence of internal deletions of protein coding sequences of mdm2 was detected in any of the normal mammary tissues or D2 murine mammary tumors examined by reverse transcription PCR (RT-PCR). Three distinct MDM2 transcripts of 6.7, 4.7 and 1.9 kb were detected in malignant human breast tissue by Northern blot analysis using a cDNA probe specific for the complete open reading frame of human MDM2. However, a cDNA probe specific for the last exon of human MDM2 hybridized only to the 6.7 and 4.7 kb transcripts, demonstrating that the 1.9 kb transcript lacked protein coding sequences contained in exon 12. Similarly, no internal deletions were detected in a panel of malignant human breast tissues using RT-PCR and analogous primers within human MDM2. Therefore, breast tumors differ from other solid tumors reported previously in that no internal deletions of MDM2 protein coding sequences were observed. However, the data document the presence of multiple MDM2 mRNA transcripts in both normal and malignant breast tissues. A subset of MDM2 transcripts were shown to lack the last exon which contains sequences coding for the RING and zinc fingers and domains which are targets for caspase-3 mediated proteolytic degradation and are required to target p53 for proteosomal degradation.

Regulation of p53 and its targets during involution of the mammary gland

Post-lactational involution of the mammary gland provides a system in which to study the expression and function of genes that regulate apoptosis in the context of a normal tissue. The functions of the p53 tumor suppressor gene have been extensively studied as a mediator of apoptosis in response to DNA damage, but its regulation in normal physiologic processes has been poorly characterized. Expression of p53 mRNA was shown to be among the first genes to be induced in mammary tissue following weaning of neonates. Although involution proceeds in the absence of a functional p53 gene, it is delayed compared to normal individuals. Therefore, involution can be viewed as biphasic with initial responses being sensitive to p53, whereas secondary responses being p53-independent. These observations can be exploited to determine the subset of genes that are p53-responsive and that mediate the effects of p53 in normal mammary tissue.

Delayed involution of the mammary epithelium in BALB/c-p53null mice

In mammals, weaning of neonates and subsequent milk stasis initiates removal of the secretory epithelium of the mammary gland by apoptosis. The p53 tumor suppressor gene is induced rapidly following weaning of neonates, but its role in the process of involution has not been defined. Therefore, experiments were performed to identify the cell types in which the p53 gene is expressed during involution and determine the consequences of its absence in BALB/c-p53null mice. Both p53 mRNA and protein were detected in the mammary epithelium within 48 h following weaning and resulted in an eightfold increase in levels of p21WAF1 mRNA. Induction of p21WAF1 mRNA was absent in BALB/c-p53null mice, and therefore, was shown to be p53-dependent. The BALB/c-p53null mice exhibited delayed involution of the mammary epithelium, as measured by 60% greater epithelial area compared to BALB/c-p53(wt) mice through 5 days post-weaning. The delay was transient with no differences being apparent at 7 days post-weaning. Expression of the stromal protease stromelysin-1 was unaffected by the absence of p53 suggesting that stromal responses were intact. These data demonstrate that p53 participates in the first stage of involution initiated by the epithelium itself, but does not affect the second phase during which stromal proteases are induced.

Continuing role of a frozen-tissue bank in molecular pathology

The growth of molecular diagnostics and its application in various clinical laboratories have made it necessary to standardize the methods used to freeze and store tissues used in molecular testing. It may now be advantageous to preserve fresh tissues and other specimen types in a central frozen-tissue bank so that sample preparation and storage conditions are appropriate for molecular applications and so that the specimen inventory can be efficiently managed. The pathology laboratory is a logical site for the facility because the professional and technical expertise available is focused on the complex scientific and regulatory aspects of laboratory medicine. Organizationally, the tissue-bank program should be overseen by a surgical pathologist to integrate it into routine surgical pathology activities. A member of the laboratory technical staff can serve as the tissue-bank coordinator with responsibility for systematic storage and retrieval of specimens and routine maintenance of equipment and supplies. To facilitate the tissue-freezing procedure and efficient storage of multiple types of specimens, 2.0 ml cryogenic vials are used as the uniform storage container. All specimens are stored at -140 to -150 degrees C in the vapor phase of liquid nitrogen. The specimen inventory data are maintained with a computerized program specifically designed to manage complex specimen storage. A frozen-tissue bank is easily implemented in a pathology laboratory and is a valuable institutional asset for diagnostic and research purposes.

The role of androgen receptor gene mutations in male breast carcinoma

Certain germline mutations (607Arg-Gln, 608Arg-Lys) in the androgen receptor gene have been associated with the occurrence of breast cancer in males suffering from partial androgen insensitivity. To assess whether somatic mutations in this gene could be detected in breast carcinoma, archival tumor tissue of males without clinical evidence of androgen insensitivity was screened for point mutations in the androgen receptor gene. DNA was retrieved by chloroform-phenol extraction from formalin-fixed, paraffin-embedded tissues. Exons 2-8 of the androgen receptor gene, encoding the DNA- and hormone-binding regions of the receptor, were amplified by polymerase chain reaction and subjected to nonisotopic single strand conformation assay (SSCA) to screen for point mutations. In the tumor DNA, no variations suggestive of mutations were encountered on SSCA. However, in a control patient with partial androgen insensitivity and predominantly female phenotype, the germline mutation 607Arg-Gln was identified in blood leukocyte DNA. Our results indicate that somatic mutations of the androgen receptor are not required for the development of male breast cancer. This, however, does not exclude an increased risk of breast carcinoma in patients with androgen insensitivity.

Ring chromosomes in dermatofibrosarcoma protuberans are composed of interspersed sequences from chromosomes 17 and 22

Ring chromosomes are found in most dermatofibrosarcoma protuberans (DFSPs), and recent reports demonstrate that portions of the DFSP ring chromosomes derive from chromosome 17. In this study we characterized ring chromosomes in three DFSPs using a combined approach of karyotyping, chromosome painting, and comparative genomic hybridization. Chromosome painting demonstrated that the ring chromosomes in each DFSP were composed of discontinuous, interwoven sequences from chromosomes 17 and 22. Amplification of chromosomes 17 and 22 sequences was confirmed in each of these cases by comparative genomic hybridization, and over-representation of chromosomes 17 and 22 sequences was also demonstrated by comparative genomic hybridization in 1 of 2 cytogenetically unremarkable DFSPs. We conclude that amplification of chromosomes 17 and 22 sequences, in ring form, is a characteristic aberration in DFSP.

Specimen storage and the use of a relational database

Advances in genetic research make laboratory specimens a valuable source of DNA. Regulations call for quick turnaround time in locating stored specimens. Personal computers and database software make it possible to store, locate, and inventory samples efficiently and assist in research work and cooperation between laboratory sites.

Platelet-derived growth factor in fibrous musculoskeletal disorders: a study of pathologic tissue sections and in vitro primary cell cultures

Despite the great variability in the clinical behavior of fibrous lesions of the musculoskeletal system, they are composed of cytologically similar fibrocytes. Receptors for estrogen or progesterone, or both, are present in some of these lesions and some increase their rate of growth during periods of high levels of sex steroid hormones. The platelet-derived growth factor-B (PDGF-B) proto-oncogene encodes the B chain of PDGF, a mitogen for fibrocytes. Tissue from aggressive fibromatosis, fibrous dysplasia, plantar fibromatosis, and recurrent plantar fibromatosis was analyzed with use of the polymerase chain reaction and in situ hybridization for the expression of PDGF-B and PDGF beta receptor. Cell culture was used to determine if estrogen and progesterone stimulation modulated the expression of PDGF-B. Aggressive fibromatosis, fibrous dysplasia, and recurrent plantar fibromatosis expressed PDGF-B; plantar fibromatosis, normal plantar fascia, normal fascia lata, and mature scar did not. All of the tissues expressed PDGF beta receptor. The level of expression in aggressive fibromatosis and fibrous dysplasia was four times that in the recurrent plantar fibromatosis. Estrogen and progesterone stimulation in aggressive fibromatosis resulted in an increase in the level of expression. Therefore, the detection of PDGF-B may be an adjunct in the pathologic identification of locally invasive lesions. Its production may be a common mechanism leading to a fibroproliferative response through deregulation of the control of growth by both paracrine and autocrine mechanisms.

Equipment and organization of a frozen tissue bank--an update

The growth of molecular diagnostics and its application in various clinical laboratories has made it necessary to standardize the methods used to freeze and store tissues used in molecular testing. It may now be advantageous to preserve fresh tissues and other specimen types in a central frozen tissue bank so that sample preparation and storage conditions are appropriate for molecular applications and so that the specimen inventory can be efficiently managed. The pathology laboratory is a logical site for this facility since the professional and technical expertise available is focused on the complex scientific and managerial aspects of laboratory medicine. Organizationally, the tissue bank program should be overseen by a surgical pathologist in order to integrate it into routine surgical pathology activities. A member of the laboratory technical staff can serve as the tissue bank coordinator with responsibility for systematic storage and retrieval of specimens and routine maintenance of equipment and supplies. In order to facilitate the tissue freezing procedure as well as efficient storage of multiple types of specimens, 2.0 ml cryogenic vials are used as the uniform storage container. All specimens are stored at -140 to -150 degrees C in the vapor phase of liquid nitrogen. The specimen inventory data are maintained with a computerized program specifically designed to manage complex specimen storage. A frozen tissue bank is easily implemented in a pathology laboratory and is a valuable institutional asset for diagnostic and research purposes.

Molecular biology of brain tumors

Molecular technology has opened new vistas in the analysis of brain tumors. It appears that, for most tumors, there is a complex interaction between two sets of genes--the oncogenes and tumor suppressor genes. The successive mutation and loss of these genes lead to the multistep process of tumor formation. In this article, current understanding of the genetic aberrations in a number of primary human brain tumors is discussed.

Neu oncogene expression in ovarian tumors: a quantitative study

We studied neu mRNA expression by slot blot analysis and protein product expression by capture ELISA and immunohistochemistry in 57 primary and metastatic ovarian neoplasms, two paraovarian leiomyosarcomas, and eight normal ovaries. Some 61% of ovarian tumors but none of the paraovarian neoplasms or normal ovaries overexpressed neu mRNA. A total of 96% of the ovarian tumors that overexpressed neu were of epithelial type. Epithelial ovarian tumors had significantly higher amounts of the neu oncogene product as determined by capture ELISA than either germ cell and stromal tumors or normal ovaries (p less than 0.025). Different subtypes of ovarian carcinomas had significantly different amounts of neu oncogene product as measured by capture ELISA; endometrioid tumors had the highest, and poorly differentiated carcinomas not otherwise specified had the lowest (p less than 0.025). ELISA values, mRNA overexpression, and immunohistochemical staining intensity did not correlate with stage at diagnosis or architectural or nuclear grade in ovarian tumors. We conclude that capture ELISA is a simple, effective way to measure the neu oncogene protein product and that there is a good correlation between ELISA levels and immunohistochemical staining intensity. However, ELISA values did not correlate with stage or histologic prognostic factors in ovarian neoplasms.