Transforming growth factor beta 1 induces squamous carcinoma cell variants with increased metastatic abilities and a disorganized cytoskeleton

Previous studies indicated that mouse transformed keratinocytes undergo an epithelial-fibroblastic conversion when cultured in the presence of TGF-beta1. This conversion is associated in vivo with a squamous-spindle carcinoma transition. We derived epithelioid (A6, FPA6) and spindle (B5) clonal cell variants from a squamous carcinoma cell line (PDV) after treatment with TGF-beta1. FPA6 cells were isolated from the ascites fluid of an A6-tumor-bearing mouse. FPA6 and A6 cell lines produced in nude mice mixed carcinomas with a squamous and poorly differentiated component. Both cell lines coexpressed keratins and vimentin and synthesized E-cadherin protein, although FPA6 cells cultured at early passages (FPA6-ep) had reduced levels of E-cadherin mRNA and increased synthesis of keratin K8, a marker of malignant progression. Immunofluorescence analysis revealed that FPA6-ep cells exhibited a disorganized cytoskeleton with keratins forming focal juxtanuclear aggregates and loss of F-actin stress fibers and cortical bundles, and E-cadherin was localized in the cytoplasm out of cell-cell contact areas. Sporadic cells in A6 and PDV cultures also presented those anomalous keratin structures, suggesting that FPA6 cells originated from a subpopulation of A6 tumor cells that metastasized into the peritoneal cavity. The analysis of the spontaneous and experimental metastatic potentials of the cell lines showed that epithelioid and fibroblastic cell variants had acquired metastatic abilities compared to PDV which was nonmetastatic. The FPA6-ep cell line exhibited a highly aggressive behavior, killing the animals at about 17 days after intravenous injection of the cells into athymic mice. The phenotype of FPA6-ep cells was unstable and reverted at later passages in which the normal organization of keratin and F-actin in filaments and the localization of E-cadherin at cell-cell contacts were restored. This phenotypic reversion occurred concomitantly with a reduction of the experimental metastatic potential of FPA6 cells.     

Human bone cells stimulate the growth of human breast carcinoma cells

Human breast cancer cells were cultured together with their metastatic target, bone tissue, to analyze possible growth promotion effects. The coculture of human osteosarcoma cells (TE-85) with human mammary carcinoma cells (ZR-75.1) resulted in up to 8.4-fold stimulation of proliferation of the breast tumor cells. Cell contact of the two cultures was permitted through the channels of Nuclepore filters. However, physical contact turned out not to be necessary, since the proliferative stimulus was also mediated by a bone-derived diffusible factor. Conditioned medium (CM), collected from human primary bone cultures, enhanced the rate of proliferation of several breast tissue cell lines (ZR-75.1, BT-20, HBL-100), while some lines were not affected by osteoblast CM. Breast tissue lines responding to bone CM express low to intermediate levels of the c-erbB-2 gene, in contrast to nonstimulated lines, which overexpress the gene. Recent observations of metastatic spread in breast cancer patients suggest a distinctive pattern of secondary tumor distribution in association with c-erbB-2 protein expression. Bone tissue seems to be a preferential target for metastases of c-erbB-2-negative breast tumors.     

Differential inhibition by hyperammonemia of the electron transport chain enzymes in synaptosomes and non-synaptic mitochondria in ornithine transcarbamylase-deficient spf-mice: restoration by acetyl-L-carnitine

These studies were undertaken to assess the relative expression and autocrine activation of the epidermal growth factor receptor (EGFR) in normal and transformed prostatic epithelial cells and to determine whether EGFR activation plays a functional role in androgen-stimulated growth of prostate cancer cells in vitro. EGFR expression was determined by Western blot analysis and ELISA immunoassays. Immunoprecipitation of radiophosphorylated EGFR and evaluation of tyrosine phosphorylation was used to assess EGFR activation. The human androgen-independent prostate cancer cell lines PC3 and DU145 exhibited higher levels of EGFR expression and autocrine phosphorylation than normal human prostatic epithelial cells or the human androgen-responsive prostate cancer cell line LNCaP. PC3 and DU145 cells also showed higher levels of autonomous growth under serum-free defined conditions. Normal prostatic epithelial cells expressed EGFR but did not exhibit detectable levels of EGFR phosphorylation when cultured in the absence of exogenous EGF. Addition of EGF stimulated EGFR phosphorylation and induced proliferation of normal cells. LNCaP cells exhibited autocrine phosphorylation of EGFR but did not undergo significant proliferation when cultured in the absence of exogenous growth factors. A biphasic growth curve was observed when LNCaP cells were cultured with dihydrotestosterone (DHT). Maximum proliferation occurred at 1 nM DHT with regression of the growth response at DHT concentrations greater than 1 nM. However, neither EGFR expression nor phosphorylation was altered in LNCaP cells after androgen stimulation. In addition, DHT-stimulated growth of LNCaP cells was not inhibited by anti-EGFR. These studies show that autocrine activation of EGFR is a common feature of prostatic carcinoma cells in contrast to normal epithelial cells. However, EGFR activation does not appear to play a functional role in androgen-stimulated growth of LNCaP cells in vitro.     

Growth-inhibitory effects of transforming growth factor-beta 1 on myeloid leukemia cell lines

Transforming growth factor-beta1 is a pleiotropic cytokine involved in a variety of biological processes in both transformed and normal cells, including regulation of cellular proliferation and differentiation; its predominant action on hematopoietic cells is to inhibit cell growth. We used growth factor-dependent cell lines to assess TGF-beta1 effects on human myeloid leukemia cell growth. While four lines were completely or predominantly resistant, TGF-beta1 inhibited effectively, albeit to various extents, the growth of 12 other cell lines. This effect was dose dependent and specific, because a neutralizing anti-TGF-beta1 antibody prevented TGF-beta1-induced growth suppression. In the present system, basic fibroblast growth factor, known as an antagonist of TGF-beta1 counteracting its inhibitory effects, did not abrogate the suppressive effects of TGF-beta1. Other growth-stimulatory cytokines negated the TGF-beta1-induced inhibition in several cell lines, again to various extents. When proliferation was enhanced by growth-promoting cytokines (e.g. granulocyte-macrophage colony-stimulating factor, GM-CSF, stem cell factor, SCF, or PIXY-321), some previously TGF-beta1-sensitive cell lines acquired cellular resistance toward TGF-beta1-mediated growth suppression, whereas four other cell lines remained susceptible to TGF-beta1 growth inhibition despite possible counteraction by other cytokines. Thus, three growth response patterns to TGF-beta1 were seen: (1) constitutive resistance; (2) factor-dependent relative resistance; and (3) sensitivity to growth inhibition indifferent to counteracting cytokines. In the latter case, TGF-beta1 did not downregulate expression of one specific growth factor receptor. These studies indicate that human myeloid leukemia cells, represented here by leukemia cell lines as model systems, exhibit heterogeneous growth responses to TGF-beta1; its inhibitory effects can be modulated or completely alleviated by positive antagonistic cytokines. The availability of TGF-beta1-susceptible and -refractory cell lines allows for detailed investigations on the mechanisms of these regulatory pathways, the nature of TGF-beta1-resistance, and the possible contribution of acquired TGF-beta1-resistance to disease progression.     

Relation of epidermal growth factor receptor concentration to growth of human esophageal cancer cell lines

The relation between the concentration of epidermal growth factor (EGF) receptor and the effects of EGF on cell proliferation were studied using 16 newly established human esophageal cancer cell lines. According to 125I-EGF binding assay, the amount of EGF receptor was found to vary from 6 x 10(4) to 1.2 x 10(7) (sites/cell). Changes in EGF-stimulated tyrosine-specific protein kinase activity almost paralleled changes in the number of EGF receptors per cell. Amplification of EGF receptor gene was detected in only one cell line. Under monolayer culture conditions, we found three types of growth responses of esophageal cell lines to EGF; growth in 5 cell lines was inhibited and that in 4 cell lines was stimulated while that in the other 7 cell lines remained unaffected. Relation was observed between the number of EGF receptors per cell and the growth response to EGF. On the other hand, cell lines whose growth was inhibited by EGF in monolayer culture were stimulated by EGF in soft agar culture, though the opposite was not necessarily true.     

Effects of modulation of basic fibroblast growth factor on tumor growth in vivo

BACKGROUND: Recombinant human basic fibroblast growth factor (rHu-bFGF) is known to stimulate proliferation in some tumor cells and to modulate tumor vascularization. PURPOSE: The purpose of this study was to examine the possible role of this agent in the development of tumors. The study was designed to determine the effects of modulating bFGF activity in vivo in tumor models from cell lines with different responses to bFGF and with different content and receptor levels of bFGF. METHODS: Two tumor cell lines (human DLD-2 colon carcinoma and rat C6 glioma) were characterized for bFGF content and bFGF receptor levels by Western blot analysis in cultured cells and by studies of [125I]rHu-bFGF binding to sections from xenografts grown in nude mice. Tumor cell proliferation was monitored after treatment with rHu-bFGF or the DG2 or DE6 IgG monoclonal antibody to rHu-bFGF in culture and in vivo. RESULTS: C6 cells exhibited 7800 high-affinity receptors for rHu-bFGF per cell (dissociation constant [Kd] = 46 pM), while DLD-2 cells lacked high-affinity receptors. rHu-bFGF stimulated [3H]thymidine uptake by C6 cells, but the addition of DG2 IgG prevented this stimulation; rHu-bFGF had no effect on [3H]thymidine incorporation by DLD-2 cells. C6 cells had higher levels of immunoreactive bFGF than did DLD-2 cells. The xenografts from both cell lines exhibited high-affinity [125I]rHu-bFGF binding that was concentrated on vascular-like structures. rHu-bFGF at a dosage of 0.25 mg/kg given intraperitoneally daily for 18 days caused a twofold increase in DLD-2 tumor weight but had little effect on the growth of C6 xenografts. In contrast, daily intravenous injections of DG2 IgG given to mice had no effect on DLD-2 tumor growth but reduced growth of C6 tumors by approximately 30%--a statistically significant difference. CONCLUSIONS: The addition of exogenous rHu-bFGF or of a neutralizing antibody resulted in significant alterations in tumor growth in vivo, which were specific for tumor type and bFGF characteristics. While some of these effects may be mediated by the bFGF-responsive endothelial cells of the tumor vasculature (DLD-2 colon carcinoma), others may result from inhibition of bFGF-dependent tumor cell proliferation (C6 glioma). IMPLICATIONS: Studies that measure tumor blood flow are necessary to confirm that these effects are mediated by changes in tumor vasculature.     

Selective growth of transformed cell lines by rat liver perfusate

Perfused rat liver releases growth-promoting activity for viral, spontaneous, and chemically transformed cells. After 5 days of incubation with perfusate, cell lines 3T12-NY (a spontaneous fibroblast transformant), NQ-T1 (a chemically transformed fibroblast line), W-8 (a chemically transformed epithelial rat liver cell line increase in cell growth above controls. Their respective normal counterparts: 3T3 Cl 42, A31-714, K-16, and HEF are not so stimulated. Within another set, the virally transformed mouse fibroblast cell line, SV3T3, exhibits a 27-fold increase in growth; however, 3T3 (mouse, fibroblasts), Py3T3 (polyomatransformed 3T3 cells), SV-Fl2-101 (a flat revertant line), and SV-Py-3T3 (a doubly transformed line) are nonresponsive. Perfused rat liver also release survival activity for SV-3T3 cells. The growth-stimulating activity in liver perfusate is selective for transformed cells. It is suggested that the liver may play a role in suporting neoplasia in vivo.     

Interleukin-6-mediated autocrine growth promotion in human glioblastoma multiforme cell line U87MG

Human glioblastoma multiforme cell lines, brain tumor biopsy tissue, and normal human fetal brain synthesize interleukin (IL)-6 and IL-6 receptor (IL-6R). Neither of these is expressed in human neurons or neuroblastoma cell lines in culture. Astrocytes from fetal brain grown in culture retain the ability to synthesize IL-6 but do not express IL-6R as inferred from RT-PCR and Southern blot studies. Coexpression of IL-6 and IL-6R in the glioblastoma cell line U87MG is confirmed by immunofluorescence staining. Both specific monoclonal antibodies against IL-6 and IL-6R and antisense oligonucleotide to IL-6 mRNA inhibit the growth of U87MG cells in culture, suggesting the existence of a functional autocrine growth loop. Anti-IL-6 antibodies also inhibit the growth of glioblastoma cell lines U373 and U118. The expression of IL-6 by human fetal astrocytes in culture is highly suggestive of its role as an oncofetal protein responsible for rapid proliferation of fetal and tumor cells but not cells of adult brain.     

The role of vascular endothelial growth factor and interleukins in the pathogenesis of severe ovarian hyperstimulation syndrome

Recent studies have suggested that the proliferation of malignant gliomas may result from activation of protein kinase C (PKC)-mediated pathways; conversely, inhibition of PKC may provide a strategy for blocking tumor growth. In the current studies, we examined the effect of a novel PKC inhibitor, calphostin C, which is a selective, highly potent, photo-activatable inhibitor of the PKC regulatory domain, on the proliferation and viability of three established and three low-passage malignant glioma cell lines, four low-passage low-grade glioma cell lines, and in adult human and neonatal rat non-neoplastic astrocyte cell lines in vitro. Under light-treated conditions, calphostin C consistently inhibited cell proliferation in each of the tumor cell lines and in the neonatal rat astrocyte cell line with a 50% effective concentration of 30 to 50 ng/ml (40 to 60 nm), which was comparable to the previously reported median inhibitory concentration (IC50) for PKC inhibition by calphostin C. Complete elimination of proliferation was achieved at concentrations of 50 to 100 ng/ml (60 to 125 nM). Cell viability decreased sharply with calphostin C concentrations of 100 to 300 ng/ml (125 to 380 nM). In contrast, under light-shielded conditions, calphostin C had a comparatively modest effect on cell proliferation and viability, with a median effective concentration of approximately 300 ng/ml. No significant inhibition of proliferation was noted in the non-neoplastic adult astrocyte cell line under either light-treated or light-shielded conditions. These findings provide further evidence that PKC may play an essential role in mediating the proliferation of both benign and malignant glioma cells in vitro and may also contribute to the proliferation of non-neoplastic immature astrocytes. Light-sensitive inhibition of proliferation and viability by agents such as calphostin C may provide a novel strategy for applying photodynamic therapy to the treatment of neoplastic glial cells.     

Autonomous growth in serum-free medium and production of hepatocellular carcinomas by differentiated hepatocyte lines that overexpress transforming growth factor alpha 1

Transforming growth factor alpha (TGF-alpha) is a polypeptide closely associated with hepatocyte proliferation in vivo and in vitro. In order to investigate the mechanisms by which TGF-alpha contributes to hepatocyte replication and transformation, we isolated hepatocytes from mice bearing a human TGF-alpha transgene and examined their growth properties and gene expression in defined, serum-free culture. The transgenic hepatocytes continued to overexpress human TGF-alpha mRNA and peptide, and were able to proliferate without exogenous growth factors in primary culture, in contrast to nontransgenic mouse hepatocytes. In short-term culture the transgenic hepatocytes underwent 1 wave of DNA replication at 72-96 h in culture before senescing, similar to nontransgenic hepatocytes supplemented with epidermal growth factor. Constitutive expression of TGF-alpha rendered the transgenic hepatocytes unresponsive to further growth stimulation by exogenous TGF-alpha, as well as other mitogens such as epidermal growth factor and hepatocyte growth factor. However, it did not alter their sensitivity to growth inhibition by TGF beta 1, 2 and 3. The addition of nicotinamide to the culture medium enabled both transgenic and epidermal growth factor-supplemented normal hepatocytes to replicate repeatedly and survive for > or = 2 months in primary culture while maintaining differentiated traits. From these long-term primary cultures of transgenic and nontransgenic hepatocytes, we established immortalized cell lines (designated TAMH and NMH lines, respectively). Both lines continued to express differentiated adult hepatocytic markers such as albumin, alpha-1-antitrypsin, transferrin, and connexin 26 and 32 mRNAs, but also expressed mRNAs for the oncofetal markers alpha-fetoprotein and insulin-like growth factor II. Unlike the near-diploid NMH hepatocyte line, the transgenic TAMH hepatocyte line was quasi-tetraploid, strongly expressed human TGF-alpha mRNA, and was highly tumorigenic in nude mice. Well-differentiated hepatocellular carcinomas developed in nude mice given injections of the TAMH line, and these appeared similar to the primary liver tumors seen in TGF-alpha transgenic mice with regard to histology and strong expression of mouse and human TGF-alpha, insulin-like growth factor II, and alpha-fetoprotein mRNAs. Our data show that TGF-alpha overexpression causes autonomous hepatocyte proliferation and contributes to neoplasia but that additional cellular alterations must occur for carcinogenesis. Inappropriate expression of insulin-like growth factor II may constitute one of these steps. The TGF-alpha transgenic mouse hepatocyte line TAMH appears to undergo transformation in a similar manner to that of hepatocytes overexpressing TGF-alpha in vivo, and should serve as an ideal system in which to study hepatocarcinogenesis.     

Human GMP synthetase. Protein purification, cloning, and functional expression of cDNA

GMP synthetase is a key enzyme in the de novo synthesis of guanine nucleotides. Human GMP synthetase has been purified to homogeneity, and a cDNA encoding the enzyme has been isolated from the T-lymphoblastoma cell line, A3.01. The open reading frame encodes a protein of 693 amino acids with a predicted molecular weight of 76,725. The cDNA complements a guaA mutant of Escherichia coli, which lacks a functional GMP synthetase and extracts from the transformed E. coli exhibit GMP synthetase activity, which is absent in the parental strain. RNA hybridization analysis shows that human GMP synthetase is encoded by a single 2.4-kilobase message. DNA hybridization analysis suggests that the human GMP synthetase is encoded by one gene. In several human cell lines, the level of mRNA expression is substantially higher in proliferating, transformed cells than in nontransformed cells. In two transformed cell lines, treatment with phorbol ester inhibits proliferation and results in a dramatic down-regulation in the levels of GMP synthetase mRNA and protein.     

Lack of effect of hematopoietic growth factors on human breast epithelial cell growth in serum-free primary culture

A number of recombinant cytokines believed to regulate normal hematopoiesis are now being used in cancer treatment protocols to reduce the myelosuppressive toxicity of intensive chemoradiotherapy regimens. It is widely assumed that such cytokines are relatively specific for hematopoietic cells, although some cell lines derived from a variety of non-hematopoietic human tumors can respond to some of these factors. However, relatively little is known about their ability to stimulate (or inhibit) the proliferation of freshly isolated normal or malignant non-hematopoietic cells. We have used a serum-free culture medium that selectively supports the growth of human breast epithelial cells (HBEC) obtained directly from normal or malignant tissue samples to evaluate potential stimulatory or inhibitory effects of eight cytokines: granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, Steel factor, interleukin-2, interleukin-3, interleukin-6, transforming growth factor-beta and macrophage inflammatory protein-1 alpha, on these cells cultured both in the presence of epidermal growth factor, a potent stimulator of HBEC growth, and in its absence. HBEC growth was assessed after 7 and 14 days using the tetrazolium-dye reduction assay. Potential effects on the well studied MCF-7 breast cancer cell line, cultured under the same conditions, were also investigated. None of the cytokines (which were tested over a wide range of concentrations) had any modulating effect on the growth of normal or malignant HBEC under the conditions used with the exception of transforming growth factor-beta, which was consistently and significantly inhibitory.(ABSTRACT TRUNCATED AT 250 WORDS)     

The roles of cytokines and retinoic acid in the regulation of human thyroid cancer cell growth

The purpose of this study was to investigate the effects of cytokines and retinoic acid in human thyroid cancer cell growth. Cellular proliferation studies of the CGTH W-1 and SW 579 cell lines were performed with various cytokines and all-trans retinoic acid (RA). Cell number was determined by cell counting and incorporation of [3H]thymidine into DNA. Inhibitory effects of tumour necrosis factor alpha (TNF-alpha) were found in both cell lines. SW 579 was more sensitive to TNF-alpha. The SW 579 cell line revealed gradually decreased cell proliferation in [3H]thymidine incorporation studies as TNF-alpha concentration increased. In contrast, the CGTH W-1 cell line revealed prominent suppressive effects when the TNF-alpha concentrations increased over 1 ng/ml. An inhibitory effect of interleukin 1 beta (IL-1 beta) on CGTH W-1 cells was noted at the concentration of 1 ng/ml, however, IL-1 beta failed to demonstrate an inhibitory effect in SW 579 cells.     

Underexpression of a novel gene, dia2, impairs the transition of Dictyostelium cells from growth to differentiation

Hepatocyte growth factor/scatter factor (HGF/SF) is a multifunctional cytokine with mitogenic, motogenic, and morphogenic activities. In addition, HGF/SF inhibits the proliferation of some tumor cell lines, but its mechanism remains poorly understood. We determined in this study whether HGF/SF induces cell death of a Meth A mouse sarcoma cell line in vitro, whose proliferation is remarkably suppressed by HGF/SF. Inhibition of Meth A cell growth by HGF/SF was dose-dependent and maximal at a concentration of 30 ng/ml. The percentage of dead cells increased to 22% upon treatment with 30 ng/ml of HGF/SF for 96 h, whereas that in untreated cultures was less than 5%. Staining of these cells nuclei with Hoechst 33342 revealed condensation of the chromatin and nuclear fragmentation. Gel electrophoresis of DNA from HGF/SF-treated cells showed a typical ladder pattern. Cells with a fractional DNA content also increased five-fold in the HGF/SF-treated cultures as analyzed by flow cytometry after propidium iodide staining. These are features typical of apoptosis. Concurrent addition of 12-O-tetradecanoylphorbol 13-acetate (TPA) with HGF/SF augmented the apoptosis induced by the growth factor, while TPA alone caused little death. This enhancement was largely blocked by addition of the specific protein kinase C inhibitor GF 109203X. These results indicate that HGF/SF induced the apoptotic cell death of the Meth A sarcoma cell line and that protein kinase C activation augmented the growth factor-induced apoptosis.     

Inhibition of growth of primary human tumour cell cultures by a 4-anilinoquinazoline inhibitor of the epidermal growth factor receptor family of tyrosine kinases

The epidermal growth factor receptor (EGFR) is thought to mediate the action of the mitogens EGF and tumour growth factor-alpha (TGF-alpha) in a variety of cancers, including those of the lung, breast and ovary. A number of new selective inhibitors of EGFR tyrosine kinase have now been developed as potential new antitumour agents. We used a potent inhibitor of this tyrosine kinase, 6-amino-4-[(3-bromophenyl)amino]-7-(methylamino)quinazoline (SN 25531; PD 156273), to determine the responses of primary cultures derived from patients with cancer of the lung, ovary, breast, cervix and endometrium. Cells were cultured in 96-well plates and proliferation assessed by incorporation of 3H-thymidine. Measured growth inhibitory concentrations IC50 values) varied from 1 nM to 14 microM with a 1000-fold differential between sensitive and resistant cultures. Results were compared with rates of proliferation, estimated using a paclitaxel-based method. We also measured the IC50 values for the tyrosine kinase inhibitor using a number of established human cell lines, and compared them with EGFR content using fluorescent antibody staining and flow cytometry. The presence of EGFR was found to be necessary, but not sufficient, for in vitro response. Only a small number of cell lines (3 of 7 for lung, 1 of 7 for ovarian, 2 of 3 squamous cell and 0 of 12 for melanoma) were sensitive to the tyrosine kinase inhibitor. In contrast, 40 of the 50 primary cultures (including 14 of 15 lung cancer samples and 14 of 19 ovarian cancer samples) were sensitive.     

Personality and social competency following unilateral stroke

To understand the nature and extent of oncogene involvement in the development of neoplasia, an experimental model of goat ovarian granulosa cells stimulated by LH was chosen. In the course of these studies, several cell lines were developed which were essentially non-tumorigenic primary cell lines. One of them, however, was spontaneously transformed being immortalized and tumorigenic. These cell lines, transformed and non-transformed, should serve as contralateral cell lines to study differential oncogene expression in hormonally induced cell proliferation, and elucidate possible hormone-oncogene nexus which may be operative in the genesis of cancer. In the present report, we have studied expression of c-myc, c-ras, c-myb, c-fos and c-sis cellular oncogenes in the cell lines by immunocytochemistry using monoclonal antibodies. In the rest of our text we refer to these cellular oncogenes as oncogenes. The results reveal differential expression of the oncogenes. The striking difference between the non-transformed AIMS/GRXII cells and the transformed AIMS/GRXVIII cells was the absence of ras protein expression in the transformed AIMS/GRXVIII cells which intensely expressed the c-myc, c-myb, c-fos, and c-sis proteins. c-ras protein was expressed in the non-transformed AIMS/GRXVIII cell line and primary cultures. c-myc protein was expressed exclusively in the AIMS/GRXVIII transformed cells. The myc activity seen in the transformed cell line may be correlated to cell proliferation. These results show the variation of phenotype in cell lines derived from a single tissue source.