RAS enzyme-linked immunoblot assay discriminates p21 species: a technique to dissect gene family expression

Apoptosis-related gene and protein expression in human lymphoma xenografts (Raji) after low dose rate radiation using 67Cu-2IT-BAT-Lym-1 radioimmunotherapy

Despite low radiation dose rates, radioimmunotherapy (RIT) has proven particularly effective in the treatment of malignancies, such as lymphoma. Apoptosis has been suggested to be a major mechanism for cell death from continuous low-dose rate radiation from radioimmunotherapy. The goal of this study was to examine Raji lymphoma xenografts for induction of apoptosis and modulation of apoptosis-related gene and protein expression in response to 67Cu-2IT-BAT-Lym-1 RIT. In preclinical and clinical trials, 67Cu-2IT-BAT-Lym-1 has shown an exceptionally long tumor residence time associated with substantial cumulated radiation doses. The Raji model mirrors human lymphomas that have mutant p53 and increased BCL2 expression. Untreated athymic BALB/c nu/nu mice and mice treated with 400 micrograms Lym-1, or 335-500 microCi 67Cu on less than 400 micrograms Lym-1 antibody, were observed for toxicity and response over 84 days. Subgroups of 4-5 mice were sacrificed at 3, 6 and 24 h after therapy so that tumors could be examined for poly(ADP-ribose) polymerase (PARP) and DNA ladder evidence for apoptosis and for BCL2, p53, p21, GADD45, TGF-beta 1 and c-MYC gene and protein expression. Untreated tumors had little evidence of apoptosis and Lym-1 had no effect on apoptosis or gene expression. 67Cu-2IT-BAT-Lym-1 RIT induced an overall response rate of 50% with tolerable toxicity, and 29% of the tumors were cured at cumulated tumor radiation doses of about 1800 cGy. Apoptosis was greatly increased in the RIT treated Raji xenografts as evidenced by cleavage of PARP to the characteristic 85 kD fragment at 3 and 6 h and by the DNA cleavage pattern. BCL2 gene and protein expression were substantially decreased at 3 and 24 h, respectively, after 67Cu-2IT-BAT-Lym-1 RIT despite only modest cumulated radiation doses (56 cGy at 3 h). Evidence for apoptosis preceded tumor regression by 4-6 days. In these therapy-resistant, human lymphoma tumors treated with 67Cu-2IT-BAT-Lym-1, apoptosis was convincingly demonstrated to be a major mechanism for the effectiveness of RIT and occurred by p53-independent mechanisms.

Exogenous E2F expression is growth inhibitory before, during, and after cellular transformation

To gain insight into the tumor suppressor properties of E2F1, we investigated growth inhibition by the E2F family of transcription factors using a tissue culture model system. We first show that exogenous E2F expression causes an 80% decrease in NIH3T3 colony formation and activated c-Ha-Ras-mediated focus formation. Inhibition of Ras-mediated transformation was dependent upon E2F DNA binding activity but did not require amino- or carboxy-terminal E2F1 protein interaction domains. Because E2F upregulation has been suggested to be associated with a neoplastic phenotype, it was possible that increased E2F activity would not be inhibitory to previously transformed cells. However, we found that exogenous E2F was also inhibitory to growth of NIH3T3 cells previously transformed by Ras or Neu. Further characterization revealed that exogenous E2F expression is inhibitory at very early times after transfection, causing dramatic losses in transfected cell populations. Interestingly, those few cells which do establish appear to be unaffected by the overexpressed E2F. Therefore, we propose that increased E2F activity may only be tolerated in a subset of cells which have acquired specific alterations that are dominant over E2F-mediated growth inhibition.

Increased expression of a high molecular weight (130 KD) protein kinase C isoform in a differentiation-defective ras-transfected keratinocyte line

The role of ras on protein kinase C (PKC) signaling was examined in two keratinocyte cell lines. Increasing the level of extracellular calcium from 0.15 mM to 1.0 mM induces some features of differentiation in the spontaneously immortalized HaCaT line, but fails to do so in a c-H-ras-transfected subline (ras-HaCaT). Raising extracellular calcium also induced a transient increase in membrane-associated PKC activity 5 min after calcium addition, in HaCaT, but not in the ras-HaCaT cells. Partial purification of PKC from the membrane/particulate fraction revealed the major isoform expressed in HaCaT to be an 80 KD species recognized by the anti-PKC alpha antibody. In ras-HaCaT, the major expressed isoform is a 130 KD species recognized by the PKC beta antibody. The kinase activity of the partially purified high molecular weight PKC is phospholipid dependent but calcium independent. Further evaluation of PKC in the HaCaT and ras-HaCaT membrane/particulate cell fraction by immunoblotting using affinity-purified antibodies against PKC alpha, beta, delta, epsilon and zeta revealed a 130 KD band reacting with the PKC delta antibody. Increased expression of this high molecular weight protein was observed in ras-HaCaT. Immunoprecipitation of PKC in ras-HaCaT using the PKC delta antibody also revealed a 130 KD species. Analysis of the PKC delta immunoprecipitate demonstrated a phospholipid, but not calcium-dependent kinase which autophosphorylated. These results suggest that the 130 KD protein may be a novel (calcium-independent) PKC (nPKC) isoform and increased expression in the ras-transfected HaCaT may be a consequence of oncogenic ras expression. This 130 KD species may also play a role in the ras-associated inhibition of differentiation in HaCaT.

Phosphorothioate oligonucleotides reduce melanoma growth in a SCID-hu mouse model by a nonantisense mechanism

In our efforts to investigate the biologic role of Ha-ras oncogenes in human melanoma by Ha-ras phosphorothioate antisense oligonucleotides, we observed that antisense, sense, and scrambled control oligonucleotides at a concentration of 10 microM all similarly and strongly inhibited growth of our human melanoma target cell line SK-2 in vitro but without specific decrease of the target protein. Cell numbers with respect to the untreated control were reduced by 84% +/- 4.2% (ISD), 82.9% +/- 3.6%, and 84% +/- 3%, respectively. In vivo studies in a SCID-hu mouse model confirmed these findings. Both antisense and sense control oligonucleotides administered through osmotic pumps significantly (p < 0.006) reduced the mean tumor weight (1.5 g +/- 0.4 g and 1.8 g +/- 0.8 g, respectively) in comparison with saline-treated (5.7 g +/- 0.7 g) or untreated control animals (5.8 g +/- 1.0 g). The vascularity of oligonucleotide-treated tumors was greatly reduced. Clinical signs of oligonucleotide-related toxicity were not observed, and there was no evidence of histopathologic alterations in a variety of mouse tissues. We could demonstrate that the antimelanoma effects can be abrogated in vitro by adding basic fibroblast growth factor (bFGF). In the context of the importance of bFGF in melanocyte biology and angiogenesis, we argue in favor of an interaction between polyanionic phosphorothioate oligonucleotides and bFGF in our melanoma system. These findings stress the notion that phosphorothioate oligonucleotides may be promising antineoplastic lead compounds capable of employing antitumor effects by mechanisms other than specific inhibition of gene expression.

c-Ha-rasEJ transfection of rat aortic smooth muscle cells induces epidermal growth factor responsiveness and characteristics of a malignant phenotype

Although the role of several protooncogenes, including sis, myc, and myb in the regulation of growth and differentiation of vascular cells has been examined in some detail, limited information is available on the contribution of ras genes to these processes. In the present studies the influence of oncogenic ras transfection on the phenotypic expression of rat aortic smooth muscle cells (SMCs) was examined. Cultured rat aortic SMCs during early passage (P4) were transfected by lipofection with c-Ha-rasEJ in a pSV2 neo vector or with pSV2 neo vector alone. Stable transfectants were selected in G418 over a 6-week period. Oncogene-transfected cells (ras-LF-1) exhibited differences in morphology and growth pattern relative to vector controls (neo-LF-1), or naive SMCs, including the development of prominent processes and the appearance of focal cellular arrangements giving rise to latticelike structures. Southern analysis revealed multiple integration of oncogenic ras in ras LF-1 cells. Transfection of c-Ha-rasEJ was associated with a twofold increase in p21 levels relative to pSV2 vector controls demonstrating that exogenous ras was expressed in these cells. Overexpression of ras p21 afforded SMCs a lower serum requirement for growth compared to vector controls, anchorage independent growth on soft agar, and acquisition of epidermal growth factor (EGF) responsiveness. Stimulation of serum-deprived SMCs with 5% fetal bovine serum (FBS) increased steady-state levels of c-Ha-ras mRNA in both ras-LF-1 and neo-LF-1 but ras induction was more pronounced in ras-transfected cells. alpha-smooth muscle (SM) actin gene expression was markedly reduced in ras-transfected cells relative to vector controls. These results show that transfection of c-Ha-rasEJ into aortic SMCs induces an altered phenotypic state characterized by alterations in growth factor-related signal transduction and tumorigenic potential.

Immunodetection of the p21-ras products in human normal and preneoplastic tissues and solid tumors: a review

Immunohistochemical detection of p21-ras to identify and characterize preneoplastic or neoplastic lesions in human tissues is reviewed. Information concerning the commercially available antibodies is presented. Antibodies DWP, Ras-10, Y13-259, YA6-172, NCC-001, and NCC-004 are fully documented with respect to their behavior in appropriate specificity tests and appear to be reliable reagents. After reviewing the data we have identified three groups of tissues or organs with respect to positive immunostaining for p21-ras as the significant criterion of malignancy. These three groups comprise (1) tissues for which no definite conclusion could be drawn (colon, lung, bladder, ovary, and neural and odontogenic tissues) despite occasional claims to the contrary, (2) tissues for which conclusions were negative (pancreas and stomach), and (3) tissues for which p21-ras staining positively discriminated malignant from normal tissues (liver, uterus, and salivary gland). Immunohistochemically detectable levels of products from a mutated ras gene could be demonstrated in a fraction of the samples from colon, lung, and bladder carcinomas, as well as in some histologically normal tissues adjacent to a colon carcinoma. The possibility that a higher relative intensity of the immunostaining reaction for p21-ras might discriminate malignant tissues from normal tissues or benign lesions in breast, pancreas, stomach, lung, uterus, or thyroid samples is suggested. Further studies now appear warranted and a strategy is proposed to validate the conclusions reached thus far.

An in vitro model of ovarian epithelial carcinogenesis: changes in cell-cell communication and adhesion occurring during neoplastic progression

To investigate the cellular mechanisms of ovarian epithelial carcinogenesis, a series of progressively transformed rat ovarian surface epithelial (ROSE) cell lines were developed and studied. Transfection of primary ROSE cells and an immortalized ROSE line (ROSE 199) with the pSV3neo plasmid (SV40 T-antigen) yielded transformed lines which retained epithelial morphology. In vivo selection of these pSV3neo cell populations resulted in further phenotypic transformation. Transfection of ROSE 199 with pSV2neo/c-H-rasEJ (rasEJp21) resulted in a malignant line which appeared fibroblast-like and formed invasive sarcomas both in athymic mice and in immunocompetent rats. Gap junctional intercellular communication (GJIC) and cell-cell adhesion were studied in this series of ROSE lines. Both c-H-rasEJ-transformation and in vivo selection resulted in a significant reduction of GJIC between adjoining cells and a transition of in vitro migration as continuous epithelial sheets to the dissociation of individual cells. This apparent shift in cell adhesiveness was associated with reduced expression of the E-cadherin adhesion molecule. Our data suggest that neoplastic progression of the ovarian surface epithelium may be associated with concomitant reductions in GJIC, E-cadherin expression and functional adhesiveness.

Cooperativity of SV40 T antigen and ras in progressive stages of transformation of human fibroblasts

Human diploid fibroblasts immortalized by SV40 T antigen provide an experimental system for studying the progression and synergism in transformation by secondary oncogenes. We have utilized the human fibroblast line HAL, which was immortalized with an orgin-defective SV40 genome encoding a temperature-sensitive T antigen, to study the cooperativity between SV40 T antigen and the ras oncogene in the progression of transformation. This study demonstrates that HAL cells possess characteristic growth patterns, requiring 10% serum, are anchorage dependent, and express a temperature-sensitive T antigen. HAL cells rely on the normal functioning of T antigen for continual growth and therefore do not proliferate at 39 degrees C. Three new derivatives of the HAL cell line were generated by microinjection of the ras oncogene. The cell line v-ras-HAL was derived by microinjection of HAL cells with v-Ha-ras DNA. The cell lines c-rasSVneo-HAL and c-rasLTRhygro-HAL were established by microinjection of HAL cells with the plasmids pSV2neoT24 or fpHVT24, respectively, wherein the ras gene is transcriptionally regulated by the cellular promoter and driven by either the SV40 enhancer or an upstream LTR enhancer. The three ras containing cell lines grow in reduced serum concentrations (0 to 5%), are anchorage independent, and express both T antigen and ras p21. The v-ras-HAL and c-rasSVneo-HAL cell lines are still dependent upon the normal functioning of T antigen for continual growth at 39 degrees C, however the c-rasLTRhygro-HAL cell line does proliferate at 39 degrees C in 10% serum-containing medium. Therefore, we propose that neither v-Ha-ras nor c-ras can replace T antigen at 39 degrees C; rather T antigen and ras cooperate in progressive stages of transformation of human fibroblasts.

Bladder cancer. Human leukocyte antigen II, interleukin-6, and interleukin-6 receptor expression determined by the polymerase chain reaction

The prediction of tumour biology rarely rests upon a single characteristic of the malignancy. The analysis of a single gene can complement standard histologic evaluation. The investigation of new parameters as well as the routine clinical analysis of gene expression is often limited because of the small amount of tissue available. This is particularly true of de novo human bladder cancers because they are generally small or handled in such a way as to hinder the analysis of multiple different parameters. Analysis of expressed mRNA by the polymerase chain reaction (RNA/PCR) is a method that allows the development of a profile of bladder cancer gene expression. The authors report the use of the RNA/PCR method to examine in bladder cancer the expression of the human leukocyte antigen (HLA) class II gene family (HLA-DR, DQ, and DP) as well as interleukin-6 (IL-6) and the interleukin-6 receptor (IL-6R). All de novo transitional cell carcinomas, one squamous carcinoma, and two transitional cell carcinoma cell lines expressed the majority of HLA class II genes. All samples expressed IL-6R RNA whereas production of IL-6 message was limited to one of the cell lines and to the high-grade bladder cancers. These results were combined with stage, grade, and DNA content to develop a profile of the cancers examined. Although an improved predictive index based on gene expression analysis by RNA/PCR has not been realized, a broader survey of human tumors for expression of these genes and others is likely to refine the classification of bladder cancer.

ras p21 expression in ovine pulmonary carcinoma

We have adapted an enzyme-linked immunoblot assay (ELIBA) for the detection of a c-ras proto-oncogene and oncogene protein products in human cell lines and tumors of 21,000 daltons molecular weight (p21ras) to studies of tissues derived from sheep. In the ELIBA, a double antibody system is used in which p21ras proteins are initially immunoprecipitated from protein extracts with monoclonal antibodies, and subsequently identified using additional anti-ras antibodies. Binding is identified with a non-radioactive enzyme-linked colorimetric detection system. In the present study, the ELIBA system was used to study twenty-seven ovine lung specimens, representing normal lung, inflammatory, and neoplastic lesions. We detected p21ras protein expression in every tissue examined, but the nature and amount of the protein product varied significantly among the tissues examined. Some tissues expressed multiple ras species. Broncho-alveolar carcinoma specimens were most likely to express c-Ki-ras proteins. Mutant proteins of c-N-ras and c-Ki-ras were detected in several bronchoalveolar carcinoma specimens, based on migrational differences between mutant and normal proteins in 15% polyacrylamide gels. The results of this study demonstrate the utility of the ELIBA system for detection of c-ras expression in ovine lung tissues, and demonstrate the ability of the system to discriminate specific ras protein species. The prognostic significance of ras expression in sheep pulmonary carcinoma has yet to be determined.