Pharmacological inhibitors of mammalian fatty acid synthase suppress DNA replication and induce apoptosis in tumor cell lines.

Pharmacological inhibitors of the anabolic enzyme, fatty acid synthase (FAS), including the natural product cerulenin and the novel compound c75, are selectively cytotoxic to cancer cells via induction of apoptosis, apparently related to the tumor cell phenotype of abnormally elevated fatty acid synthetic metabolism. As part of a larger effort to understand the immediate downstream effect of FAS inhibition that leads to apoptosis, the effects of these inhibitors on cell cycle progression were examined. Both FAS inhibitors produce rapid, profound inhibition of DNA replication and S phase progression in human cancer cells. The dose responses for fatty acid synthesis inhibition and DNA synthesis inhibition are similar. The kinetics of both effects are rapid, with fatty acid synthesis inhibition occurring within 30 min and DNA synthesis inhibition occurring within 90 min of drug exposure. Meanwhile, apoptotic changes are not detected until 6 h or later after inhibitor exposure. Fatty acid synthetic pathway activity and the magnitude of DNA synthesis inhibition by FAS inhibitors are increased in parallel by withdrawal of lipid-containing serum from the cultures. The mechanism of DNA synthesis inhibition by cerulenin is indirect, because expression of certain viral oncogenes rescues DNA synthesis/S phase progression in cerulenin-exposed cells. The data suggest a direct linkage at a regulatory level, between fatty acid synthesis and DNA synthesis in proliferating tumor cells.

Fatty acid synthase (FAS): a target for cytotoxic antimetabolites in HL60 promyelocytic leukemia cells.

Many human cancers express elevated levels of fatty acid synthase (FAS), with correspondingly increased fatty acid synthesis and abnormal fatty acid utilization. Recent studies have shown that the FAS inhibitor, cerulenin, is selectively cytotoxic to cell lines derived from human malignancies, suggesting that those carcinoma cells are dependent upon endogenous fatty acid synthesis for growth. These data further suggest that the fatty acid synthesis pathway is a potential target for chemotherapy development. The present studies demonstrate that cerulenin cytotoxicity is mediated by fatty acid pathway inhibition. Proliferating HL60 promyelocytic leukemia cells express high levels of FAS mRNA and protein and synthesize fatty acid predominantly for membrane phospholipid. Following exposure to 12-O-tetradecanoylphorbol-13-acetate, the FAS expression in HL60 cells is abolished, fatty acid synthesis diminishes, and the cells become insensitive to cerulenin while acquiring a differentiated, macrophage-like phenotype. HL60 cells adapted to growth in serum- and fatty acid-free medium show a dose-dependent sensitivity to cerulenin, which is reversed by palmitate, the major product of FAS, indicating that cerulenin cytotoxicity is mediated through fatty acid starvation. Cells grown in the presence of exogenous fatty acid partially downmodulate FAS expression and increase mean cell volume (phospholipid mass/cell) but retain their sensitivity to cerulenin, which is reversed by 3-fold excess oleate supplementation. These results demonstrate that malignant cells can retain dependence on endogenous fatty acid synthesis and sensitivity to FAS inhibitors in the presence of physiological fatty acid levels and thus support the notion that FAS inhibitors may be useful in treating cancer in vivo.

Inhibition of fatty acid synthesis induces programmed cell death in human breast cancer cells.

One of the key limiting factors in the treatment of advanced stage human epithelial malignancies is the lack of new, selective molecular targets for antineoplastic therapy. A substantial subset of human breast, ovarian, endometrial, colorectal, and prostatic cancers express elevated levels of fatty acid synthase, the major enzyme required for endogenous fatty acid biosynthesis, and carcinoma lines are growth inhibited by cerulenin, a noncompetitive inhibitor of fatty acid synthase. We have shown previously that the difference in fatty acid biosynthesis between cancer and normal cells is an exploitable target for metabolic inhibitors in the in vitro setting and in vivo in a human ovarian carcinoma xenograft in nude mice. Here, we report that cerulenin treatment of human breast cancer cells inhibits fatty acid synthesis within 6 h after exposure, that loss of clonogenic capacity occurs within the same interval, and that DNA fragmentation and morphological changes characteristic of apoptosis ensue.

Malonyl-coenzyme-A is a potential mediator of cytotoxicity induced by fatty-acid synthase inhibition in human breast cancer cells and xenografts.

A biologically aggressive subset of human breast cancers and other malignancies is characterized by elevated fatty-acid synthase (FAS) enzyme expression, elevated fatty acid (FA) synthesis, and selective sensitivity to pharmacological inhibition of FAS activity by cerulenin or the novel compound C75. In this study, inhibition of FA synthesis at the physiologically regulated step of carboxylation of acetyl-CoA to malonyl-CoA by 5-(tetradecyloxy)-2-furoic acid (TOFA) was not cytotoxic to breast cancer cells in clonogenic assays. FAS inhibitors induced a rapid increase in intracellular malonyl-CoA to several fold above control levels, whereas TOFA reduced intracellular malonyl-CoA by 60%. Simultaneous exposure of breast cancer cells to TOFA and an FAS inhibitor resulted in significantly reduced cytotoxicity and apoptosis. Subcutaneous xenografts of MCF7 breast cancer cells in nude mice treated with C75 showed FA synthesis inhibition, apoptosis, and inhibition of tumor growth to less than 1/8 of control volumes, without comparable toxicity in normal tissues. The data suggest that differences in intermediary metabolism render tumor cells susceptible to toxic fluxes in malonyl-CoA, both in vitro and in vivo.

Inhibition of fatty acid synthesis delays disease progression in a xenograft model of ovarian cancer.

One of the key limiting factors in the treatment of advanced stage human epithelial malignancies is the lack of selective molecular targets for antineoplastic therapy. A substantial subset of human ovarian, endometrial, breast, colorectal, and prostatic cancers exhibit increased endogenous fatty acid biosynthesis and overexpress certain enzymes in the pathway. Cell lines derived from these tumors use endogenously synthesized fatty acids for cellular functions, whereas normal cells and tissues appear to utilize dietary lipids preferentially. We have previously shown that the difference in fatty acid biosynthesis between cancer and normal cells is an exploitable target for metabolic inhibitors in vitro. Here, we report observations in vivo using the i.p. model of the multiply drug-resistant OVCAR-3 human ovarian carcinoma in nude mice which demonstrate that: (a) fatty acid synthase overexpression in OVCAR-3 is comparable to levels in primary human tumors assessed by immunohistochemistry; (b) fatty acid synthetic activity of OVCAR-3 is comparably elevated in vitro and in vivo and is 4 to >20-fold higher than normal murine tissues; (c) treatment with the specific fatty acid synthase inhibitor, cerulenin, markedly reduces tumor cell fatty acid biosynthesis in vivo; (d) fatty acid synthase inhibition produces regression of established ascites tumor; and (e) treatment with cerulenin causes reduction in ascites incidence, delay in onset of ascites, and significantly increased survival (P<0.04).

Pharmacological inhibition of fatty acid synthase activity produces both cytostatic and cytotoxic effects modulated by p53.

Fatty acid synthetic metabolism is abnormally elevated in tumor cells, and pharmacological inhibitors of the anabolic enzyme fatty acid synthase (FAS), including the natural product cerulenin and the novel synthetic compound c75, are selective inhibitors of tumor cell growth. We have recently reported that these two FAS inhibitors both produce rapid, potent inhibition of DNA replication and S-phase progression in human cancer cells, as well as apoptotic death. Here we report an additional characterization of the cellular response to FAS inhibition. RKO colon carcinoma cells were selected for study because they undergo little apoptosis within the first 24 h after FAS inhibition. Instead, RKO cells exhibited a biphasic stress response with a transient accumulation in S and G2 at 4 and 8 h that corresponds to a marked reduction in cyclin A- and B1-associated kinase activities, and then by accumulation of p53 and p21 proteins at 16 and 24 h and growth arrest in G1 and G2. The response of RKO cells to FAS inhibition resembled a genotoxic stress response, but DNA damage did not appear to be an important downstream effect of FAS inhibition, because none was detected using the single cell gel electrophoresis assay (comet assay) to assess DNA damage. p53 function is probably important in protecting RKO cells from FAS inhibition because, similar to many other tumor lines, RKO cells expressing a dominant negative mutant p53 gene underwent extensive apoptosis within 24 h after FAS inhibition. Sensitization of cells to FAS inhibitors by the loss of p53 raises the possibility that these agents may be clinically useful against malignancies carrying p53 mutations. Whereas induction of apoptosis appeared related to accumulation of the substrate, malonyl-CoA, after FAS inhibition, the cytostatic effects were independent of malonyl-CoA accumulation and may have resulted from product depletion.

Large-scale serial analysis of gene expression reveals genes differentially expressed in ovarian cancer.

Difficulties in the detection, diagnosis, and treatment of ovarian cancer result in an overall low survival rate of women with this disease. A better understanding of the pathways involved in ovarian tumorigenesis will likely provide new targets for early and effective intervention. Here, we have used serial analysis of gene expression (SAGE) to generate global gene expression profiles from various ovarian cell lines and tissues, including primary cancers, ovarian surface epithelia cells, and cystadenoma cells. The profiles were used to compare overall patterns of gene expression and to identify differentially expressed genes. We have sequenced a total of 385,000 tags, yielding >56,000 genes expressed in 10 different libraries derived from ovarian tissues. In general, ovarian cancer cell lines showed relatively high levels of similarity to libraries from other cancer cell lines, regardless of the tissue of origin (ovarian or colon), indicating that these lines had lost many of their tissue-specific expression patterns. In contrast, immortalized ovarian surface epithelia and ovarian cystadenoma cells showed much higher similarity to primary ovarian carcinomas than to primary colon carcinomas. Primary tissue specimens therefore appeared to be a better model for gene expression analyses. Using the expression profiles described above and stringent selection criteria, we have identified a number of genes highly differentially expressed between nontransformed ovarian epithelia and ovarian carcinomas. Some of the genes identified are already known to be overexpressed in ovarian cancer, but several represent novel candidates. Many of the genes up-regulated in ovarian cancer represent surface or secreted proteins such as claudin-3 and -4, HE4, mucin-1, epithelial cellular adhesion molecule, and mesothelin. Interestingly, both apolipoprotein E (ApoE) and ApoJ, two proteins involved in lipid homeostasis, are among the genes highly up-regulated in ovarian cancer. Selected serial analysis of gene expression results were further validated through immunohistochemical analysis of ApoJ, claudin-3, claudin-4, and epithelial cellular adhesion molecule in archival material. These experiments provided additional evidence of the relevance of our findings in vivo. The publicly available expression data reported here should stimulate and aid further research in the field of ovarian cancer.

A binary architectural grading system for uterine endometrial endometrioid carcinoma has superior reproducibility compared with FIGO grading and identifies subsets of advance-stage tumors with favorable and unfavorable prognosis.

The International Federation of Gynecology and Obstetrics (FIGO) grading of uterine endometrial endometrioid carcinoma requires evaluation of histologic features that can be difficult to assess, including recognition of small amounts of solid growth, distinction of squamous from nonsquamous solid growth, and assessment of degree of nuclear atypia. The authors describe a novel, binary architectural grading system that uses low-magnification assessment of amount of solid growth, pattern of invasion, and presence of necrosis to divide endometrioid carcinomas into low- and high-grade tumors. The authors analyzed its performance for predicting prognosis and with respect to intra- and interobserver reproducibility. A total of 141 endometrioid carcinomas from hysterectomy specimens were graded according to the FIGO system, nuclear grading, and the binary architectural system. A tumor was classified as high grade if at least two of the following three criteria were present: (1) more than 50% solid growth (without distinction of squamous from nonsquamous epithelium); (2) a diffusely infiltrative, rather than expansive, growth pattern; and (3) tumor cell necrosis. For tumors that were confined to the endometrium, only percent solid growth and necrosis were evaluated, and those with both solid growth of more than 50% and necrosis were considered high grade. All tumors were graded independently by three pathologists on two separate occasions. Both inter- and intraobserver agreement using the binary grading system (kappa = 0.65 and 0.79) were superior compared with FIGO (kappa = 0.55 and 0.67) and nuclear grading (kappa = 0.22 and 0.41). The binary grading system stratified patients into three distinct prognostic groups. Patients with stage I low-grade tumors with invasion confined to the inner half of the myometrium (stages IA and IB) had a 100% 5-year survival rate. Patients with low-grade tumors that invaded beyond the outer half of the myometrium (stage IC and stages II-IV) and those with high-grade tumors with invasion confined to the myometrium (stages IB and IC) had a 5-year survival rate of 67% to 76%. In striking contrast to patients with advance-stage low-grade tumors, patients with advance-stage high-grade tumors had a 26% 5-year survival rate. This binary grading system has advantages over FIGO and nuclear grading that permit greater interobserver and intraobserver reproducibility and should be tested in other studies of endometrial endometrioid carcinomas to validate its reproducibility and use for segregating patients into different prognostic groups.

Fatty acid synthase (FAS) expression in human breast cancer cell culture supernatants and in breast cancer patients.

Fatty acid synthase (FAS) is selectively expressed in certain human cancers, including carcinoma of the breast, prostate, colon, ovary, and endometrium, compared to normal human tissues and therefore is a putative tumor marker. In this study, we found FAS concentrations were elevated in cell culture supernatants during cell growth in two human breast cancer cell lines but not other cancer cell lines. A quantitative enzyme-linked immunosorbent assay and Western blot analysis were employed in this study. In addition, serum FAS levels were significantly higher in breast cancer patients with different clinical stages (Stage II: 0.59+/-0.09 units/l, Stage III: 0.79+/-0.13 units/l, and Stage IV: 1.39+/-0.35 units/l) compared with healthy subjects (0.27+/-0.02 units/l, P<0.05). Taken together, our data suggest that FAS expression may be a useful tumor marker for breast cancer and play a role in assessing cancer virulence.

Comparison of estrogen and progesterone receptor, Ki-67, and p53 immunoreactivity in uterine endometrioid carcinoma and endometrioid carcinoma with squamous, mucinous, secretory, and ciliated cell differentiation.

An analysis of 77 uterine endometrioid carcinomas was performed to compare pure endometrioid carcinomas and endometrioid carcinomas with various types of cellular differentiation for the expression of estrogen (ER) and progesterone (PR) receptors, p53, and Ki-67 and to correlate these findings with clinicopathologic features. Forty-three pure endometrioid carcinomas and 34 endometrioid carcinomas displaying additional types of cellular differentiation in at least 10% of the tumor (16 squamous, 11 mucinous, four ciliated cell, and three secretory) were analyzed. In 8 of the 16 tumors with squamous differentiation, the squamous component was histologically benign (low grade), and in eight tumors it was histologically malignant (high grade). In tumors showing various types of cellular differentiation except those with a high-grade squamous component, comparison of the endometrioid glandular component with the squamous, mucinous, secretory, and ciliated cell components showed that ER/PR, Ki-67, and p53 expression were generally higher in the glandular component compared with the various differentiated components. These findings parallel the changes that occur in the endometrium in the secretory phase of the menstrual cycle and, therefore, suggest that the differentiated components have undergone terminal differentiation. In contrast, in endometrioid carcinomas with a high-grade squamous component, Ki-67 and p53 expression were the same in the glandular and squamous components suggesting that squamous epithelium in these tumors represented another pathway of cellular differentiation but not one that was terminally differentiated. Endometrioid carcinomas with a high-grade squamous component had significantly higher grade (P = .002), stage (P < .001), cellular proliferation index (P = .0005), and worse outcome (P = .0009) compared with tumors with the other types of cellular differentiation, including those with a low-grade squamous component and pure low-grade endometrioid carcinomas. In addition, carcinomas with a high-grade squamous component occurred in older women and were more frequently associated with atrophic endometrium and less replacement hormone therapy, but the differences were not statistically significant. In conclusion, endometrioid carcinomas with various types of cellular differentiation can be broadly divided into two groups. Tumors with mucinous, secretory, and ciliated cell differentiation and those with a low-grade squamous component are similar to pure low-grade endometrioid carcinomas in that most have high ER and PR expression, low cellular proliferation indices, low p53 immunoreactivity, and good prognosis. In contrast, endometrioid carcinomas with a high-grade squamous component lack expression of ER and PR, have high cellular proliferation indices, often express p53, and have a prognosis similar to poorly differentiated endometrioid carcinomas.

Clear cell carcinoma of the endometrium is characterized by a distinctive profile of p53, Ki-67, estrogen, and progesterone receptor expression.

This study was designed to analyze certain clinicopathological features and the profile of p53, Ki-67, estrogen (ER), and progesterone (PR) receptor expression of clear cell carcinoma of the endometrium and to determine whether the pathogenesis of clear cell carcinoma can be accommodated by a dualistic model of endometrial carcinogenesis. In this model, endometrioid carcinoma develops from endometrial hyperplasia under unopposed estrogenic stimulation, and serous carcinoma develops in atrophic endometrium from a putative precursor lesion designated endometrial intraepithelial carcinoma (EIC). Twenty-one clear cell carcinomas of the endometrium were analyzed and compared with 77 endometrioid carcinomas of all grades and 30 serous carcinomas. Clear cell carcinomas showed a distinctive immunoprofile characterized by immunonegativity for ER and PR, low immunoreactivity for p53, and a high Ki-67 proliferation index. ER, PR, and Ki-67 expression were similar to serous carcinoma, but p53 expression was significantly lower in clear cell carcinoma (P < .05). ER and PR expression were significantly lower, and the Ki-67 proliferation index was significantly higher in clear cell carcinoma compared with endometrioid carcinomas (P < .05). p53 expression tended to be higher in clear cell carcinoma compared with endometrioid carcinoma, but the difference was not statistically significant. In contrast to endometrioid carcinoma, clear cell carcinoma was rarely associated with endometrial hyperplasia and serous carcinoma was not. Subdividing clear cell carcinoma morphologically into one that resembled serous carcinoma (clear cell carcinoma with serous features) and another that did not (typical clear cell carcinoma) showed that clear cell carcinoma with serous features had a higher Ki-67 proliferation index than typical clear cell carcinoma, although expression of ER, PR, and p53 were similar. Clear cell carcinoma with serous features was associated with EIC in 50% and was not associated with endometrial hyperplasia. In contrast, typical clear cell carcinoma was associated with endometrial hyperplasia in 40% and was not associated with EIC. In summary, this study provides evidence that clear cell carcinoma of the endometrium, like serous carcinoma, is estrogen independent and shows a high Ki-67 proliferation index. In contrast to serous carcinoma, strong p53 expression occurred less frequently in clear cell carcinoma and predominantly in clear cell carcinoma with serous features. The findings suggest that the molecular events that underlie the development of clear cell carcinoma differ from those of endometrioid and serous carcinoma.

Partial T-cell receptor gene rearrangement. A source of pseudo-clonal populations in thymomas and other thymic tissues.

The differentiation of thymocytes into mature post-thymic T cells requires rearrangement of T-cell antigen receptor genes from germline to a spectrum of spliced configurations encoding functional receptors. In the T-cell receptor beta chain locus, this process occurs via a hierarchical series of recombination events, linking "diversity" and "joining" segments, then "variable" and "diversity" segments. The authors report Southern blot analysis of the T-cell receptor beta locus in normal human thymic tissue after restriction digestion with Bam HI identifying rearranged DNA fragments in 5 of 6 samples, which probably represent an intermediate deletion joining D beta 1 to a J beta 2 segment without rearrangement of the upstream V region. Hybridization intensity was in the range of 5% to 30% of represented DNA. Reduction of signal from bands containing C beta 1 and J beta 2 sequences after Eco RI and Hind III digestion was consistent with this model. A probe specific for J beta 1 did not hybridize with the rearranged fragment while J beta 2 specific sequences did not hybridize with the rearranged fragment while J beta 2 specific sequences did, indicating a deletion of the region of J beta 1, but limited to sequences upstream of J beta 2. Most peripheral lymphoid specimens do not demonstrate similar rearranged DNA fragments, however T-cell-rich populations may do so. Analysis of 31 additional surgically resected thymic tissues and three polyclonal T-cell-rich peripheral lymphoid specimens revealed a similarly rearranged fragment in 13 of 14 thymuses with follicular hyperplasia; 6 of 9 thymomas; 5 of 6 malignant (invasive) thymomas; 0 of 2 thymic carcinomas; and, at very low abundance, in 3 of 3 peripheral T-cell populations. Because this nongermline T-cell receptor gene apparently reflects polyclonal incomplete rearrangement, rather than clonality, awareness of this phenomenon may help prevent erroneous diagnosis of T-cell lymphoma for mediastinal lymphoid lesions with an apparent "clonal" T-cell receptor gene rearrangement. If the intermediate deletion is derived from an ongoing process, the data suggest that in many cases neoplastic thymic epithelium may retain functions necessary not only to support a resident thymocyte population, but also to activate ongoing T-cell differentiation. Alternatively, the intermediate deletion may derive from abandoned non-productive rearrangements.

Immunohistochemical expression of human erythrocyte glucose transporter and fatty acid synthase in infiltrating breast carcinomas and adjacent typical/atypical hyperplastic or normal breast tissue.

To evaluate the immunohistochemical expression of GLUT1, human erythrocyte glucose transporter 1, and fatty acid synthase (FAS), 66 human breast carcinomas and adjacent peritumoral tissue were studied. GLUT1 and FAS were expressed in 53 and 61 carcinomas, in 17 and 14 typical/atypical hyperplastic tissues, and in 16 and 13 tissues adjacent to tumor normal breast tissue, respectively. Statistical analysis revealed association between invasive carcinomas, invasive carcinomas with in situ component and GLUT1 immunostaining. GLUT1 staining was associated with tumor grade, FAS with tumor stage, and GLUT1 and FAS coexpression with tumor grade. Controls expressed no immunostaining. GLUT1 and FAS are new markers involved in the biologic activities of cancer cells. GLUT1 and FAS coexpression may indicate increased use of energy by the neoplastic cells correlated with poorly differentiated features and aggressive behavior. The innovative finding that GLUT1 and FAS are observed in mammary carcinoma adjacent nonneoplastic tissues may suggest a role in detecting initial phases of breast carcinogenesis.

Lipogenic enzymes fatty acid synthase and acetyl-coenzyme A carboxylase are coexpressed with sterol regulatory element binding protein and Ki-67 in fetal tissues.

Endogenous fatty acid synthesis has been observed in some rapidly proliferating cells and tissues, both normal and neoplastic, and probably supports membrane synthesis. Sterol regulatory element binding proteins (SREBPs) are transcription factors that regulate the expression of genes for both cholesterol and fatty acid synthesis. The inactive precursor form resides in cytoplasmic membranes. Intracellular lipid depletion triggers proteolytic cleavage of SREBP, allowing the amino terminus to enter the nucleus and activate the expression of enzymes, including acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS), major biosynthetic enzymes for fatty acid synthesis. The expression patterns of ACC, FAS, SREBP, and Ki-67 in fetal tissues were compared to determine whether SREBP is likely to participate in the regulation of proliferation-associated fatty acid synthesis during fetal growth. Tissues from 22 fetuses, 12 first-trimester and 10 second-trimester (range 7.0 to 21.6 weeks), were studied. Serial 5-microm sections were stained with antibodies to ACC, FAS, SREBP, and Ki-67 and were compared. ACC, FAS, SREBP, and Ki-67 were coexpressed in the proliferative compartments of the intestines, skin, and kidney. ACC, FAS, and Ki-67 were coexpressed with little SREBP in lung and cytotrophoblast. SREBP, ACC, and FAS were coexpressed without Ki-67 in hepatocytes, ganglion cells, and intermediate trophoblast. The close linkage of SREBP, ACC, FAS, and Ki-67 in some proliferating fetal tissues suggests that in these tissues SREBP participates in the transcriptional regulation of lipogenic genes during proliferation. SREBP, ACC, and FAS coexpression without Ki-67 occurs in differentiated tissues that may synthesize fatty acids for other functions.

Activation of the c-myb locus is insufficient for the rapid induction of disseminated avian B-cell lymphoma.

We have previously reported that infection of 9- to 13-day-old chicken embryos with RAV-1 results in rapid development of a novel B-cell lymphoma in which proviral insertion has activated expression of the c-myb gene (E. Pizer and E. H. Humphries, J. Virol. 63:1630-1640, 1989). The biological properties of these B-cell lymphomas are distinct from those associated with the B-cell lymphomas that develop following avian leukosis virus proviral insertion within the c-myc locus. In an extension of this study, more than 200 chickens, infected as 10- to 11-day-old embryos, were examined for development of lymphomas that possess disrupted c-myb loci. Fourteen percent developed disseminated B-cell lymphoma. In the majority of these tumors, the RAV-1 provirus had inserted between the first and second exons that code for p75c-myb. However, insertions between the second and third exons and between the third and fourth exons were also detected. In situ analysis of myb protein expression in tumor tissue revealed morphological features suggesting that the tumor originates in the bursa. Within the bursa, the lymphoma appeared to spread from follicle to follicle without compromising the structural integrity of the organ. Tumor masses in liver demonstrated heterogeneous levels of myb protein suggestive of biologically distinct subpopulations. In contrast to the morbidity data, immunohistological analysis of bursae from 4- to 6-week-old chickens at risk of developing lymphomas bearing altered c-myb loci revealed lesions expressing elevated levels of myb in 16 of 19 birds. The activated myb lymphoma displayed very poor capacity to proliferate outside its original host. Only 1 of 33 in vivo transfers of tumor to recipient hosts established a transplantable tumor. None of the primary tumor tissue nor the transplantable tumor exhibited the capacity for in vitro proliferation. Similar experimental manipulation has yielded in vitro lines established from avian B-cell lymphomas expressing elevated levels of c-myc or v-rel. The dependence on embryonic infection for development of activated-myb lymphoma suggests a requirement for a specific target cell in which c-myb is activated by proviral insertion. It is likely, moreover, that continued tumor development requires elevated expression of myb proteins within a specific cell population in a restricted stage of differentiation.

A frequent deletion polymorphism on chromosome 22q13 identified by representational difference analysis of ovarian cancer.

Sizable homozygous deletions (>100 bp) of genomic DNA in cancer cells are typically interpreted as an indication of the location of a tumor suppressor gene. In an effort to identify novel ovarian growth-suppressing genes, we performed representational difference analysis (RDA) of ovarian cancer cells. One of the RDA probes identified a 276-bp region of chromosome 22q deleted in 47% of the ovarian cancer cell lines examined. This small deletion was also found in the genomic DNA of 25% of colon cancer cell lines examined and, surprisingly, in 18% of the blood DNA samples from healthy controls. The deleted allele, which was named u22q, has a frequency of approximately 50% in the population and is in Hardy-Weinberg equilibrium with the intact allele. The deleted DNA sequence is flanked by direct repeats and likely originated through a slipped mispairing mechanism. The deletion did not encompass known transcripts or expressed sequence tags. It therefore appears likely that u22q represents a common polymorphism, often hemizygous in ovarian cancer because of a high rate of LOH of chromosome 22q. These findings provide an example of a sizable homozygous deletion that does not appear to be associated with disease. Such a finding provides a cautionary tale for positional cloning projects initiated exclusively on the basis of the identification of homozygous deletions. The possibility that the deletions in question may be constitutive should always be considered since it is probable that the genome contains a large number deletions/insertions of various sizes.

Expression of fatty acid synthase is closely linked to proliferation and stromal decidualization in cycling endometrium.

Estrogen-driven proliferative phase growth is the most rapid physiological proliferative process that occurs in the adult. The tissue growth that occurs during this phase of the menstrual cycle requires incorporation of a substantial quantity of fatty acid into the structural lipids of cell membranes. Fatty acid synthase (FAS) is the major biosynthetic enzyme required for de novo synthesis of fatty acids. In this immunohistochemical study, we have observed that human endometrium displays distinct patterns of FAS expression in the proliferative and secretory phases of the normal menstrual cycle. Proliferative endometrial glands and stroma show high FAS expression that closely correlates with expression of Ki-67, estrogen and progesterone receptors, supporting the view that FAS expression plays a role in cellular proliferation in response to estrogen. FAS expression declines during early to midsecretory phase, then reappears in decidualized stromal cells in late secretory phase as well as in the decidua of pregnancy. The second wave of FAS expression correlates with progesterone-receptor localization in the decidual cells, a finding suggesting a second induction of FAS expression in the endometrium, associated with differentiation, that may be regulated by progesterone.

Vascular embolization of benign granulosa cells.

OBJECTIVE(S): Most conditions involving sex cord-stromal cells can be diagnosed on morphologic criteria alone. We describe a case of vascular embolization of benign granulosa cells in which immunohistochemistry was of value as a diagnostic tool. METHODS: We reviewed the clinical history and gross pathologic findings from a 48-year-old patient who presented with abdominal pain and fullness. Formalin-fixed paraffin-embedded sections were examined by routine H&E and immunohistochemical stains. RESULTS: Histologic examination of a grossly enlarged and cystic ovary revealed nests of cells within angiolymphatic spaces. Although the cells were cohesive and atypical, they were morphologically similar to the nearby graafian follicle. Immunohistochemistry showed positive labeling with antibodies to inhibin-alpha and cytokeratin in a pattern consistent with benign granulosa cells. CONCLUSION(S): Immunohistochemical stains for inhibin-alpha and cytokeratin are useful tools to help confirm granulosa cell origin, as demonstrated in this case involving an atypical histomorphologic picture of "embolization."

Sterol regulatory element-binding protein-1 participates in the regulation of fatty acid synthase expression in colorectal neoplasia.

Endogenous fatty acid synthesis has been observed in certain rapidly proliferating normal and neoplastic tissues. Sterol regulatory element-binding proteins (SREBPs) are transcription factors that regulate the expression of lipogenic genes including fatty acid synthase (FAS), the major biosynthetic enzyme for fatty acid synthesis. We have previously shown that SREBP-1, FAS, and Ki-67, a proliferation marker, colocalized in the crypts of the fetal gastrointestinal tract epithelium. This study sought to determine whether SREBP-1 participates in the regulation of proliferation-associated fatty acid synthesis in colorectal neoplasia. An immunohistochemical analysis of SREBP-1, FAS, and Ki-67 expression in 25 primary human colorectal carcinoma specimens showed colocalization in 22 of these. To elucidate a functional linkage between SREBP-1 activation and proliferation-associated FA synthesis, SREBP-1 and FAS content were assayed during the adaptive response of cultured HCT116 colon carcinoma cells to pharmacological inhibition of FA synthesis. Cerulenin and TOFA each inhibited the endogenous synthesis of fatty acids in a dose-dependent manner and each induced increases in both precursor and mature forms of SREBP-1. Subsequently, both the transcriptional activity of the FAS promoter in a luciferase reporter gene construct and the FAS expression increased. These results demonstrate that tumor cells recognize and respond to a deficiency in endogenous fatty acid synthesis by upregulating both SREBP-1 and FAS expression and support the model that SREBP-1 participates in the transcriptional regulation of lipogenic genes in colorectal neoplasia.