Modulation of oncogenic potential by alternative gene use in human prostate cancer.

Only a small percentage of primary prostate cancers have genetic changes. In contrast, nearly 90% of clinically significant human prostate cancers seems to express high levels of the nuclear phosphoprotein pp32 by in situ hybridization. Because pp32 inhibits oncogene-mediated transformation, we investigated its paradoxical expression in cancer by comparing the sequence and function of pp32 species from paired benign prostate tissue and adjacent prostatic carcinoma from three patients. Here we demonstrate that pp32 is expressed in benign prostatic tissue, but pp32r1 and pp32r2, closely-related genes located on different chromosomes, are expressed in prostate cancer. Although pp32 is a tumor suppressor, pp32r1 and pp32r2 are tumorigenic. Alternative use of the pp32, pp32r1 and pp32r2 genes may modulate the oncogenic potential of human prostate cancer.

Resistance of neoplasms to immunological destruction: role of a macrophage chemotaxis inhibitor.

Several tissue culture lines of 6C3HED, a murine lymphoma, were more susceptible to immunologic destruction in vivo than the highly virulent 6C3HED line maintained by serial intramuscular transplantation. The attenuated tissue culture cells were rejected by normal syngeneic recipients, but thymectomized mice were unable to reject attenuated cells. In such mice, the growth rate of attenuated cells was equivalent to the growth rate of virulent cells in normal syngeneic mice. The increased susceptibility of attenuated cells to destruction by syngeneic hosts was shown to correlate with decreased production by the tumor cells of a macrophage chemotaxis inhibitor, and not with altered antigen density. In addition, when inhibitor isolated from virulent cells was administered to mice challenged with attenuated cells, the latter cells became virulent in vivo. When attenuated and virulent cells were administered simultaneously in the same host, the attenuated cells were able to develop into progressively growing tumors. The data suggest that the successful growth of neoplastic cells in normal may require tumor cells to produce factors which subvert the ability of the host to mobilize macrophages rapidly at the tumor site.

Antibody-mediated suppression of grafted lymphoma. IV. Influence of time of tumor residency in vivo and tumor size upon the effectiveness of suppression by syngeneic antibody.

In the suppression of the growth of a mouse lymphoma 6C3HED by antibody, the effectiveness of antibody in suppressing growing or established tumor cells and comparable number of freshly injected tumor cells is quantitatively similar. The effectiveness of antibody diminishes markedly when the number of tumor cells per mouse reaches the level of 10(6) due to the development of a macrophage shortage. At the 10(5) tumor cells level, antibody-mediated suppression takes place in an optimal manner and between 10(5) and 10(4) tumor cell numbers, the amount of antibody required to suppress 50% of the tumor cells is directly proportional to the number of tumor cells suppressed.

Immunotherapy of cancer with antibody.

A long-term suppression of a transplanted solid tumor that has been growing in a syngeneic animal can be achieved by the administration of antibody against the tumor. The susceptibility of such growing tumor cells to antibody treatment is similar to that of a comparable number of freshly injected tumor cells.

Structure of pp32, an acidic nuclear protein which inhibits oncogene-induced formation of transformed foci.

pp32 is a nuclear protein found highly expressed in normal tissues in those cells capable of self-renewal and in neoplastic cells. We report the cloning of cDNAs encoding human and murine pp32. The clones encode a 28.6-kDa protein; approximately two-thirds of the N-terminal predicts an amphipathic alpha helix containing two possible nuclear localization signals and a potential leucine zipper motif. The C-terminal third is exceptionally acidic, comprised of approximately 70% aspartic and glutamic acid residues; the predicted pI of human pp32 is 3.81. Human and murine pp32 cDNAs are 88% identical; the predicted proteins are 89% identical and 95% similar. Although the structure of pp32 is suggestive of a transcription factor, pp32 did not significantly modulate transcription of a reporter construct when fused to the Gal4 DNA-binding domain. In contrast, in cotransfection experiments, pp32 inhibited the ability of a broad assortment of oncogene pairs to transform rat embryo fibroblasts, including ras + myc, ras + jun, ras + E1a, ras + mutant p53, and E6 + E7. In related experiments, pp32 inhibited the ability of Rat 1a-myc cells to grow in soft agar, whereas it failed to affect ras-induced focus formation in NIH3T3 cells. These results suggest that pp32 may play a key role in self-renewing cell populations where it may act in the nucleus to limit their sensitivity to transformation.

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.

A novel M(r) 32,000 nuclear phosphoprotein is selectively expressed in cells competent for self-renewal.

We investigated the association between expression of a novel M(r) 32,000 nuclear phosphoprotein (pp32) and cell proliferation in vivo using the well-characterized physiological model of androgen-dependent regeneration of prostate in orchiectomized rats, pp32 is expressed at high levels in neoplastic cell lines and in certain anatomically defined stem cell compartments of normal human tissues such as intestinal crypt epithelial cells. Immunohistochemistry and in situ hybridization were used to monitor pp32 expression in rat ventral prostatic epithelium following castration and androgen restoration. Castrated rats retained only 6% of prostate wet weight compared to intact controls but were capable of complete gland restoration upon androgen replacement. In intact controls, pp32 expression localized to small acini at the periphery of the gland and to rare basal cells in the central regions. Ten days following castration, there was a 3,5-fold enrichment in the frequency of pp32-positive cells with greater than 56% of remaining epithelial cells expressing pp32 protein. In situ hybridization showed that all remaining epithelial cells contained pp32 mRNA. Upon testosterone replacement, pp32 expression and localization returned to that of intact controls. In order to determine the association between pp32 expression and cell division, DNA synthesis was monitored by bromodeoxyuridine incorporation during prostate involution and regeneration. Bromodeoxyuridine incorporation peaked 3 days after androgen replacement and occurred diffusely throughout the gland. Thus, pp32-positive cells are anatomically distinguishable from the population of terminally differentiating cells undergoing rapid expansion. Preliminary immunohistochemical studies of human prostatic neoplasia demonstrated increased expression of pp32 in human prostatic adenocarcinoma and prostatic intraepithelial neoplasia compared to benign prostatic hypertrophy and normal human prostate. The highest degree of expression occurred in the higher Gleason grades and prostatic intraepithelial neoplasia. This work suggests that pp32 is a nuclear protein which has a selective but presently undefined role in cells competent for self-renewal.

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.

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).

Tumor suppression and potentiation by manipulation of pp32 expression.

Alternative use of genes of the closely-related pp32 family is a common occurrence in human prostate cancer. pp32r1 and pp32r2, the oncogenic members of the pp32 family, are expressed in prostatic adenocarcinoma, while adjacent benign prostate continues to express pp32. This study focuses upon the role of pp32 in tumor suppression. We demonstrate that antisense inhibition of pp32 in NIH3T3 cells leads to a variety of phenotypic changes associated with transformation including reduced serum dependence and loss of contact inhibition. NIH3T3 cells with antisense-inhibited pp32 are not tumorigenic, but are markedly more susceptible to oncogenic stimuli such as ras. In contrast, constitutive expression of pp32 abolishes ras mediated transformation in vitro and tumorigenesis in vivo. These data demonstrate, from the functional aspect, that pp32 acts as a tumor suppressor. Furthermore, inactivation of pp32 function through alternative gene use may be a critical event in tumor evolution and progression.

Enzymes of the fatty acid synthesis pathway are highly expressed in in situ breast carcinoma.

Expression of high levels of fatty acid synthase (FAS), an important enzyme in fatty acid synthesis, has been identified in a wide variety of human carcinomas. In breast and prostate carcinoma, FAS expression appears to be associated with aggressive disease. Recent biochemical studies have demonstrated that FAS expression in cancer cells connotes activation of the entire fatty acid synthesis pathway leading to the production of palmitic acid. Here, we explore the immunohistochemical expression of FAS and human acetyl-CoA carboxylase (HACC), the rate-limiting enzyme in fatty acid synthesis, in breast cancer progression from histologically normal breast through the development of in situ duct and lobular carcinoma to infiltrating carcinoma. Both FAS and the Mr 275,000 isoform of HACC are expressed in a small subset of cells in normal breast lobules and terminal ducts. Upon development of either in situ duct or lobular carcinoma, FAS and both isoforms of HACC are expressed at higher levels and in a majority of the cells. These findings suggest that expression of the enzymes of fatty acid synthesis are frequently altered early in the progression of human breast carcinoma.

pp32 overexpression induces nuclear pleomorphism in rat prostatic carcinoma cells.

Nuclear pleomorphism is an important diagnostic factor in tumour pathology. Traditionally, nuclear pleomorphism is evaluated qualitatively or semiquantitatively, often as a component of tumour grade; the molecular basis of nuclear pleomorphism, however, remains unclear. In this study, we investigated the quantitative effects on nuclear morphology of overexpressing pp32, a recently described nuclear phosphoprotein highly expressed in self-renewing and neoplastic cell populations. Assessment of Feulgen-stained transfected and control lines of AT3.1, a rat prostatic carcinoma cell line, using a computerized Cellular Image Analysis System (BD CAS-200) showed that stable overexpression of human pp32 in AT3.1 cells is accompanied by marked increases in the coefficient of variation of nuclear shape, nuclear size and chromatin textures but not in DNA content. In contrast, stable transfection with control vector, with ras, or with bcl-2 failed to affect nuclear morphology. Cell cycle analysis further showed that pp32-related increases in variation of nuclear structure manifested principally in G1. These studies suggest that pp32 plays a role either directly or indirectly in the control of nuclear shape of G1 cells.

Expression of haptoglobin-related protein in primary and metastatic breast cancers. A longitudinal study of 48 fatal tumors.

The ability to establish a prognosis for patients with early breast cancer is an important clinical issue. Recent studies have shown that antibodies to haptoglobin-related protein (Hpr) may be useful in stratifying early patients with breast cancer according to their relative risks of recurrence. Nearly 30% of early breast cancers express proteins bearing Hpr epitopes. Hpr-positive breast cancers are more likely to recur after primary resection and are associated with shorter disease-free intervals. This immunohistochemical study examines temporal changes in Hpr expression during the course of disease in 48 patients with fatal breast carcinoma. Thirty-seven primary tumors (77%) were Hpr positive. Ten of the 11 initially negative tumors (91%) were Hpr positive at the time of recurrence. In contrast, only 10 of the 37 initially positive tumors (27%) were Hpr negative with relapse. Of 18 axillary nodes that were examined, 16 (89%) were Hpr positive; all four lymph nodal metastases in patients with initially negative primary tumors were Hpr positive. The authors conclude that the acquisition of Hpr expression parallels increased malignant potential and that Hpr expression, once acquired, tends to remain a permanent characteristic of any given mammary tumor.

Expression of oncogenic antigen 519 (OA-519) in prostate cancer is a potential prognostic indicator.

Predicting the prognosis of patients with prostate cancer is a clinically important problem. Previous studies have indicated that the expression of haptoglobin-related protein epitopes in samples of breast cancer in early stages was associated with earlier relapses and higher risk for tumor recurrence. Oncogenic antigen 519 (OA-519) is the new marker designation for molecules expressing haptoglobin-related protein epitopes. The objective of this immunohistochemical study was to examine OA-519 expression in prostate cancer samples and its relationship to the established prognostic indicators of tumor grade, tumor volume, and clinical stage. Forty-two consecutive tissue samples of prostate adenocarcinoma were examined using an affinity-purified anti-OA-519 antibody. Twenty specimens (48%) tested positive, whereas 22 (52%) tested negative. No staining was observed in normal or hyperplastic prostate tissue. Staining occurred in 6 of 9 (67%) grade III, 14 of 23 (61%) grade II, and in none of 10 (0%) grade I cases (I vs. II and/or III: Fisher exact test, P less than 0.006). Twenty-three of the 42 samples were transurethral resection specimens with cancer; 11 (48%) of these tested positive. The mean percentage of tissue chips with tumor, a measure of tumor volume, was significantly higher in the positive group (57%) than in the negative group (15%) (P = 0.004). The proportion of positively stained cases increased with advancing clinical stage, with 25% of Stage A cases expressing OA-519, and 46%, 67%, and 64% of Stages B, C, and D, respectively, expressing OA-519. OA-519 expression correlates with higher tumor grades, larger tumors, and possibly with advanced stage, and thus, it is potentially of prognostic value in prostate cancer.

In situ hybridization-theory and practice.

In situ hybridization is a technique to determine and localize target nucleic acids in morphologically preserved tissue sections. Recent advances in methods have greatly increased the sensitivity of the technique, and it is currently possible to detect extremely few copies of any given target sequence with nonisotopic methods. In this teaching review, we integrate theoretical background, technical considerations, and guidelines for usage for this important component of molecular diagnosis.

Erythrocyte protein 4.1 binds and regulates myosin.

Myosin was recently identified in erythrocytes and was shown to partition both with membrane and cytosolic fractions, suggesting that it may be loosely bound to membranes [Fowler, V. M., Davis, J. Q. & Bennett, V. (1985) J. Cell Biol. 100, 47-55, and Wong, A. J., Kiehart, D. P. & Pollard, T. D. (1985) J. Biol. Chem. 260, 46-49]; however, the molecular basis for this binding was unclear. The present studies employed immobilized monomeric myosin to examine the interaction of myosin with erythrocyte protein 4.1. In human erythrocytes, protein 4.1 binds to integral membrane proteins and mediates spectrin-actin assembly. Protein 4.1 binds to rabbit skeletal muscle myosin with a Kd = 140 nM and a stoichiometry consistent with 1:1 binding. Heavy meromyosin competes for protein 4.1 binding with Ki = 36-54 nM; however, the S1 fragment (the myosin head) competes less efficiently. Affinity chromatography of partial chymotryptic digests of protein 4.1 on immobilized myosin identified a 10-kDa domain of protein 4.1 as the myosin-binding site. In functional studies, protein 4.1 partially inhibited the actin-activated Mg2+-ATPase activity of rabbit skeletal muscle myosin with Ki = 51 nM. Liver cytosolic and erythrocyte myosins preactivated with myosin light-chain kinase were similarly inhibited by protein 4.1. These studies show that protein 4.1 binds, modulates, and thus may regulate myosin. This interaction might serve to generate the contractile forces involved in Mg2+-ATP-dependent shape changes in erythrocytes and may additionally serve as a model for myosin organization and regulation in non-muscle cells.

Microscale, filtration-type binding assay for studying myosin-erythrocyte protein 4.1 interactions.

In vitro binding of skeletal muscle myosin and the erythrocyte cytoskeleton linker protein, band 4.1, was evaluated in a novel small-volume, filtration-based binding assay. The assay equipment consisted of a plastic grid containing several buffer-filled wells into which were placed small nylon screens. Myosin was covalently tethered to an agarose (Sepharose) support and aliquots of this resin were pipetted onto the surface of the submerged nylon screen. Following addition of radiolabeled protein 4.1, and an appropriate incubation period, the myosin-Sepharose beads and bound protein 4.1 were separated by wicking the buffer from beneath the nylon screen with a piece of filter paper. Nylon screens, with adherent resin beads, and the filter paper wicks were then counted to give the amounts of bound and free protein 4.1, respectively. This system proved to be a rapid, simple, and quantitative method for evaluating the behavior of a myosin binding protein under conditions in which free myosin would be prone to assemble into filaments. Moreover, since the assay separates bound and free components within a few seconds, it is well suited for the analysis of low-affinity interactions.

Expression of haptoglobin-related protein and its potential role as a tumor antigen.

These studies describe the detection of a haptoglobin species, its characterization as the HPR gene product, and its association with both pregnancy and neoplasia. Previous work showed that the early recurrence of human breast cancer correlated with immunohistochemical staining with a commercial antiserum ostensibly directed against pregnancy-associated plasma protein A (PAPP-A). Use of this antiserum to guide purification of the putative antigen led to the present identification and purification of a strongly immunoreactive protein species distinct from PAPP-A that was present in the plasma of pregnant women at term. Unlike PAPP-A, a homotetramer of 200-kDa polypeptides, the immunoreactive protein consists of a light (alpha) chain (16.5 kDa) and a heavy (beta) chain (40 kDa); protein microsequencing of the beta chain showed it to be a member of the haptoglobin family. The alpha chain of this haptoglobin species differs from ordinary haptoglobin 1 and 2 alpha chains both structurally and immunologically and represents the product of the HPR gene, haptoglobin-related protein (Hpr), since (i) the apparent molecular mass is the same as that predicted for Hpr alpha chain, (ii) the peptide map differs from that of haptoglobin 1 in a manner predicted by the HPR nucleotide sequence, (iii) monospecific antibodies that react with epitopes shared by the unique alpha chain and a synthetic peptide derived from the HPR nucleotide sequence do not detect these epitopes in either haptoglobin 1 or 2, and (iv) sequences of alpha-chain peptides were consistent with this identification, excluding haptoglobin 1 but not haptoglobin 2. The immunohistochemical reactivity of antibodies raised to the synthetic Hpr peptide is similar to that of anti-PAPP-A. Moreover, staining of neoplastic breast tissue is abolished by preincubation with purified Hpr.

Haptoglobin-related protein (Hpr) epitopes in breast cancer as a predictor of recurrence of the disease.

The early discrimination of clinically aggressive breast cancer from indolent disease would be clinically useful. Some human breast cancers express haptoglobin-related protein (Hpr), the HPR gene product, or a substance that shares epitopes with it. We retrospectively examined the association between the expression of Hpr and the recurrence of cancer in 70 patients with early breast cancer (Stage I or II) treated by mastectomy from 1977 through 1985, using immunohistochemical analysis of routinely processed paraffin-embedded tissue and evaluating it without knowledge of the patients' status. The expression of Hpr epitopes was associated with earlier recurrence according to life-table analysis (P less than 0.0002). Progesterone-receptor status (determined in 64 patients), tumor size, clinical stage, axillary-lymphnode status, mitotic index, and tumor necrosis also predicted recurrence, but multivariate analysis showed that Hpr-epitope expression was an independent prognostic factor. Since both Hpr status and progesterone-receptor status were independent predictors of recurrence, they could be combined to stratify the cases further: breast cancer was found to have recurred in 11 of 12 patients (92 percent) who were positive for Hpr and negative for progesterone receptors, in 5 of 11 (45 percent) who were positive for Hpr and positive for progesterone receptors, and in 9 of 41 (22 percent) who were negative for Hpr, in whom progesterone-receptor status had little effect. We conclude that Hpr-epitope expression is a clinically important predictor of the recurrence of cancer in patients with early breast cancer, especially in combination with progesterone-receptor status.

Antibody-mediated suppression of tumor growth. I. Suppression by murine IgG1 isolated from alloantiserum.

The tumor suppressive activity of murine IgG1 antibody was studied in vivo. IgG1 was isolated from hyperimmune alloantisera against a murine lymphoma, 6C3HED, by absorption with heat-killed, formalinized Staphylococcus aureus. Cowan strain I, followed by DEAE ion exchange chromatography and Sephadex G-200 gel filtration chromatography. The isolated IgG1, which had no detectable IgM, IgA, IgG2a, IgG2b or IgG3, could suppress the growth of the tumor. In addition, DEAE and Sephadex G-200 column profiles of the in vivo tumor suppressive activity showed good correlation with the profiles of total IgG1 immunoglobulin and anti-tumor antibody assayed for IgG1 heavy chains and kappa light chains. The IgG1 tumor suppressive activity was not diminished after heating at 56 degrees C for 30 min.