Abolition of mevinolin-induced growth inhibition in human fibroblasts following transformation by simian virus 40.

The basal level of the gene expression and the activity of 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase was higher in SV40-transformed human fibroblasts (90-VA VI) than in normal ones (HDF). In both these cell types mevinolin (25 microM) caused an 85-90% depression of HMG CoA reductase activity and of the incorporation of [3H]acetate into sterols. In HDF this was coupled to an efficient block of cell growth, whereas the growth of 90-VA VI was only slightly reduced by mevinolin. In HDF, mevinolin (25 microM) also abolished essentially all dilichol synthesis, as measured by incorporation of [3H]acetate. In contrast, dolichol synthesis remained unaltered, or was increased, in mevinolin-treated 90-VA VI. We suggest that these different responses of dolichol synthesis may depend on different substrate affinities of the rate-limiting enzyme in the dolichol pathway. However, if 90-VA VI was treated with 25-hydroxycholesterol (25-OH), an alternative inhibitor of HMG CoA reductase, the cellular growth as well as dolichol synthesis was significantly decreased. Since the inhibitory effect of 25OH on HMG CoA reductase activity did not exceed that of mevinolin, it seems that 25-OH, besides HMG CoA reductase, inhibits steps distal to HMG CoA reductase. This notion was further supported by the finding that addition of mevalonate did not prevent the 25-OH-induced growth inhibition. However, if dolichol was added along with 25-OH, the block was partially prevented, indicating that a critical level of de novo synthesis of dolichol for cellular growth.

Increased expression of insulin-like growth factor I receptor in malignant cells expressing aberrant p53: functional impact.

We investigated the functional impact of p53 on insulin-like growth factor I receptor (IGF-IR) expression in malignant cells. Using the BL-41tsp53-2 cell line, a transfectant carrying temperature-sensitive (ts) p53 and endogenous mutant p53 (codon 248), we demonstrated a drastic down-regulation of plasma membrane-bound IGF-IRs on induction of wild-type p53. However, a similar response was obtained by treatment of BL-41tsp53-2 cells expressing mutant ts p53 with a p53 antisense oligonucleotide. Thus, even if the negative effect of wild-type p53 predominates under a competitive condition, these data indicate that mutant p53 may be important for up-regulation of IGF-IR. To further elucidate this issue, three melanoma cell lines (BE, SK-MEL-5, and SK-MEL-28) that overexpressed p53 were investigated. The BE cell line has a "hot spot" mutation (codon 248) and expresses only codon 248-mutant p53. SK-MEL-28 has a point mutation at codon 145. SK-MEL-5 cells did not exhibit any p53 mutations, but the absence of p21Waf1 expression suggested functionally aberrant p53. Our data suggest that interaction with Mdm-2 may underlie p53 inactivation in these cells. Using p53 antisense oligonucleotides, we demonstrated a substantial down-regulation of cell surface expression of IGF-IR proteins in all melanoma cell lines after 24 h. This was paralleled by decreased tyrosine phosphorylation of IGF-IR and growth arrest, and, subsequently, massive cell death was observed (this was also seen in BL-41tsp53-2 cells with mutant conformation of ts p53). Taken together, our results suggest that up-regulation of IGF-IR as a result of expression of aberrant p53 may be important for the growth and survival of malignant cells.

Evidence for protein dolichylation.

Labeling of human colon carcinoma cells with [3H]dol, followed by extensive delipidation and removal of dol-P oligosaccharides, showed that dol are bound to cellular proteins with sizes of 5, 10, 27, 75 and > 140 kDa. HPLC purification of proteolytic products of [3H]dol- and [35S]cys-labeled proteins revealed a hydrophobic peak containing both dol and cysteine. The dol/cys-labeled products were clearly separated from GG-cys, and exhibited a hydrophobicity between that of dol-P and dol. In another set of experiments delipidated proteins were treated with methyl iodide, which cleaves thioether bonds. After HPLC purification of released dol-like lipids, these were subjected to mass spectrometry. This demonstrated molecular ions with the same mass as that of dol. Taken together our data provide evidence for the existence of proteins covalently modified with dol.

Tamoxifen-induced cell death in malignant melanoma cells: possible involvement of the insulin-like growth factor-1 (IGF-1) pathway.

Recent data indicate that the estrogen receptor (ER) blocker tamoxifen (TAM) can induce cell death in malignant melanoma cells. However, as shown in the present study and several other studies melanoma cells usually do not express classical ERs. In the present study we investigated whether the cytotoxic effect of TAM on melanoma cells could depend on interference with the expression or function of the insulin-like growth factor-1 receptor (IGF-1R), a plasma membrane receptor important for cell survival in this tumor cell type. Several melanoma cell lines were included in the analysis. Administration of TAM at a concentration of 15 microm or more resulted in cell death of the melanoma cells within 48 h. TAM treatment was correlated to a slight to moderate inhibition of IGF-1 binding to IGF-1R. Since it has been reported that TAM can increase the release of IGF binding proteins (IGFBPs) we then investigated whether this mechanism could underly the decreased IGF-1 binding. However, we could demonstrate that the amount of released IGFBPs were unchanged or decreased in TAM-treated cells. Whereas TAM did not have any strong effect on IGF-1 binding and the expression of IGF-1R at the cell surface, it was was found to efficently block tyrosine phosphorylation of IGF-1R beta-subunit. Taken together, our data suggest that TAM-induced cytotoxicity of malignant melanoma cells can be due to inactivation of IGF-1R.

Factors released from human breast-cancer cells counteract the inhibitory effects of mevinolin on DNA-synthesis and morphology but not on hmg coa reductase-activity.

Treatment with mevinolin (an HMG CoA reductase inhibitor) blocks proliferation and causes characteristic morphological changes in human breast cancer cells (MDA231). In this study we demonstrate that the conditioned medium of these cells contains factors that stimulate DNA synthesis and normalize morphology in mevinolin-treated cells, without reducing the inhibition of HMG CoA reductase activity. These data suggest that the breast cancer cells produce and release mevalonate-derived products which influence DNA synthesis and morphology. By undertaking a simple purification of the conditioned medium we could demonstrate that the effects on DNA synthesis and morphology were mediated by different compounds.

Specific and sensitive detection of the EWS/FLI1 fusion protein in Ewing's sarcoma by Western blotting.

We applied Western blotting, using an antibody against the carboxy terminal of the FLI1 protein, for detection of the 68-kDa EWS/FLI1 fusion protein in cultured Ewing's sarcoma cells and in four surgical biopsies of Ewing's sarcoma. Of six different human cell lines, the 68-kDa fusion protein was identified only in Ewing's sarcoma cells carrying the t(11;22)(q24;q12) translocation. The four samples from Ewing's sarcoma patients were also found to contain the 68-kDa fusion protein. The lowest detection level for total protein loaded on the gel was 0.3 microg. When whole Ewing's sarcoma cells were used for Western blotting without prior protein extraction, the lowest detection level was 1,300 cells. It will be possible to use Western blotting for detection of the EWS/FLI1 fusion protein in the diagnosis of Ewing's sarcoma in surgical biopsy specimens, and possibly also in fine-needle aspirates. As the method is not dependent on the quality of mRNA in the sample and involves no risk of contamination, it will be a powerful complement to the reverse-transcription polymerase chain reaction (RT-PCR).

A highly aggressive primitive mesenchymal tumor with a translocation (1;19)(q12;q13.2).

Soft tissue sarcomas constitute a heterogeneous group of malignant tumors of mesenchymal origin, the classification of which may present a diagnostic challenge. We present here the cytological, histopathological, immunohistochemical, and cytogenetic findings of an unusual case of a highly aggressive sarcoma. Based on the morphology and the immunohistochemical profile, this primitive tumor and its metastases could not be conclusively classified as any of the defined subtypes of sarcomas, although the findings were suggestive of a variant of rhabdomyosarcoma. Cytogenetic characterization using G-banding, SKY, FISH, and CGH revealed almost identical chromosomal compositions of the primary tumor and the metastasis. The hypertetraploid karyotype was characterized by numerical imbalances as well as by an unbalanced translocation t(1;19)(q12;q13.2), which has not been previously reported.

Utility of a proliferation marker in distinguishing between benign naevocellular naevi and naevocellular naevus-like lesions with malignant properties.

In the present study we have investigated the utility of the proliferation marker MIB 1 in distinguishing between benign naevocellular naevi and naevocellular naevus-like lesions with malignant potential. Percentages of MIB 1 immunoreactivity in the intradermal portion of the lesions were determined. In benign congenital and acquired naevi, as well as in dysplastic naevi, there was no or only a slight intradermal melanocytic proliferation (0-2%), whereas vertical growth phase melanomas exhibited a substantial proliferative activity (11-48%). In five cases of naevus-lke lesions, which had all relapsed as unmistakable malignant melanomas (locally or metastatically) after primary surgery, there was also clear proliferative activity (9-67%). Our findings suggest that MIB 1 may be a useful tool in the routine histopathological examination of problematic naevocellular lesions.

Expression of the insulin-like growth factor-1 receptor and its anti-apoptotic effect in malignant melanoma: a potential therapeutic target.

The insulin-like growth factor-1 receptor (IGF-1R) and its possible protective effect on apoptotic cell death in malignant melanoma was analysed in four commercial melanoma cell lines. Inhibition of N-linked glycosylation by tunicamycin, which has previously been shown to block the translocation of IGF-1R to the cell surface, blocked cell growth and/or induced cell death in these cell lines. Treatment with alphaIR-3, an antibody blocking the binding domain of IGF-1R, also resulted in growth arrest and/or apoptosis. We also analysed lymph node metastases of malignant melanoma by Western blotting and immunohistochemistry. All these cases were shown to express IGF-1R at the cell surface. In three cases of lymph node metastases we had access to both tumour specimens and cultured cells. One of these exhibited a substantially higher expression of IGF-1R than the two other cases. The corresponding cell lines showed growth arrest and apoptosis following treatment with alphaIR-3. However, the two cell lines with low expression of IGF-1R were more sensitive in this respect. Furthermore, we demonstrated an inverse correlation between IGF-1R expression and the frequency of apoptotic cells in the tumour specimens. Our data suggest that IGF-1R is crucial for the viability of malignant melanoma cells in vitro as well as in vivo.

Requirement for mevalonate in the control of proliferation of human breast cancer cells.

The proliferative rate as well as the activity of 3-hydroxy-3-methylglutaryl CoA (HMG CoA) reductase, which regulates de novo synthesis of mevalonate, was comparable in the two human breast cancer cell lines Hs578T and MDA-231 when cultured in the presence of serum. Upon treatment with mevinolin (an HMG CoA reductase inhibitor) the proliferation of the cell lines was depressed with similar dose response kinetics. A depression of the enzymatic activity to a level of 1-1.5 pmol mevalonate/min/mg protein decreased DNA-synthesis by approximately 90%. In contrast, at slightly higher enzymatic activities, ie 2-2.5 pmol/min/mg protein, there was only a mild decrease in DNA-synthesis. Addition of mevalonate to a final concentrations of 0.77 mM completely prevented the mevinolin-induced block on cell proliferation in both cell lines. Exposure to serum-free medium caused by itself a depression of HMG CoA reductase activity to 2.5-3 pmol/min/mg protein in both cell lines. Whereas the proliferation of MDA-231 was not inhibited at all by serum depletion, this treatment decreased DNA-synthesis in Hs578T by nearly 80%. Interestingly, the addition of mevalonate also prevented this growth inhibition in Hs578T, irrespective of whether mevinolin was present or not. However, this required a 30-fold increase in the mevalonate concentration (23.1 mM) as compared to MDA-231. The present data indicate that mevalonate is not only necessary for cell proliferation, but also that mevalonate is involved in the serum-dependent control of cell proliferation in serum-sensitive cells. In this respect, serum seems to affect the utilization of mevalonate in the formation of mevalonate-derived growth-regulatory molecules, rather than regulating the de novo synthesis of mevalonate.

Reverse transcriptase polymerase chain reaction on fine needle aspirates for rapid detection of translocations in synovial sarcoma.

OBJECTIVE: To evaluate the utilization of fine needle aspiration (FNA) biopsy to obtain material for reverse-transcriptase polymerase chain reaction (RT-PCR) in the detection of the t(X;18)(p11.2;q11.2) translocation in synovial sarcomas. STUDY DESIGN: We applied RT-PCR to detection of synovial sarcoma fusion gene transcripts on fine needle aspirates. Five clinical samples were first analyzed: one was a tumor previously diagnosed as malignant hemangiopericytoma, one was a poorly defined tumor, and three were suspected synovial sarcomas. FNA material was transferred directly to the RT-PCR reaction tube without RNA extraction. RESULTS: The t(X;18) translocation could be detected on the limited amount of material that FNA provides. In each of the cases studied the representivity of the tumor samples was confirmed microscopically. CONCLUSION: Our protocol permits analysis directly on representative samples without extraction of RNA. The results imply that RT-PCR offers reliable detection of sarcoma fusion gene transcripts on fine needle aspirates. The procedure, apart from being applicable to outpatients, is rapid and sensitive.

Dolichol delays G1-arrest for one cell cycle in human fibroblasts subjected to depletion of serum or mevalonate.

It is well-established that some product(s) or metabolite(s) of mevalonate is (are) critical for growth of mammalian cells. In the search for this (these) compound(s) it seems meaningful to distinguish between compounds needed for cell cycle progression in proliferating cells and compounds needed for growth activation of arrested cells. By using time-lapse video recording we have studied the possible regulatory role of cholesterol, dolichol and mevalonate in the cell cycle of human diploid fibroblasts (HDF). HDF, which are serum-dependent, were rapidly growth-arrested in the first part of G1 upon removal of serum factors. They also responded to mevinolin (an HMG CoA reductase inhibitor) by a similar G1-block, indicating that a mevalonate-derived product is involved in the G1-located cell cycle control of HDF. Interestingly, dolichol counteracted the G1-block caused by both types of treatment. Hence, the early G1-cells could traverse the remainder of the cell cycle and divide despite depletion of serum or mevalonate. We also demonstrated that addition of dolichol resulted in a significant decrease in the rate of protein degradation. This protein stabilizing effect may constitute the mechanism by which dolichol delays the G1-arrest of HDF.

Characterization of hydrophobic prenyl groups of isoprenylated proteins in human cancer cells.

Extensive protease digestion of delipidated [3H]mevalonate (MVA)-labeled proteins, followed by HPLC separation of the products, is one approach to identify and study prenyl cysteines. Using this methodology three major [3H]MVA-labeled peaks appeared. Two of them represent farnesyl cysteine (FC) and geranylgeranyl cysteine (GGC). The third peak represents unknown products that are considerably more hydrophobic than FC and GGC, here designated HPC. Previously, we provided evidence that cysteine residues may also be modified by dolichyl groups. Dolichyl cysteines (DolC) belong to HPC. However, as shown in the present study, DolC only represents a minor portion of HPC. Data obtained from different sets of experiments, including [3H]GGOH-labeling and use of prenyl transferase inhibitors, suggest that HPC mainly involves CXC or CC residues with double-linked GG groups. In turn this points to the possibility that proteins modified by double GG groups are quite common, and may probably involve other proteins than the rab family of GTPases.

Dietary arachidonic acid protects mice against the fatty liver induced by a high fat diet and by ethanol.

Five groups of NMRI mice were fed ethanol or sucrose in a nutritionally adequate liquid diet for 9 days. The dietary fat consisted of olive oil with the fatty acid composition 18:1 77%, 18:2 10%, 18:0 and 16:0 12%. The ethanol treated groups received 5% w/v ethanol (E) or isocaloric sucrose (S). Two groups (S- and E-) received the diet without supplement. In two groups (S+ and E+) 7% of the fat was exchanged for arachidonic acid (20:4). In a fifth group (IE+) treated with ethanol and arachidonic acid the diet also contained indomethacin (10 mg/l). The mean intake of ethanol was about 20 g/kg/day. After 9 days animals were killed and liver lipids analyzed after Folch extraction. The post mortem accumulation of prostaglandin E2 in the kidney was measured by GC-MS. Dietary 20:4 was found to protect mice against fatty liver caused both by a high fat diet alone and in combination with ethanol. The liver triglycerides were 30.7 +/- 4.3 (S-), 46.1 +/- 6.9 (E-), 6.8 +/- 0.4 (S+) and 19.4 +/- 1.8 (E+). Prostaglandin levels in the kidney were depressed by ethanol treatment. Indomethacin gave variable degrees of PG synthesis inhibition. The degree of liver triglyceride accumulation in the IE+ group was inversely proportional to the degree of PG synthesis. The data suggest a role for liver 20:4 cyclooxygenase metabolites in fatty liver caused by high fat diets and ethanol.

Pre-operative radiotherapy in soft tissue tumors. Assessment of response by static post-contrast MR imaging compared to histopathology.

PURPOSE: To evaluate if static post-contrast MR imaging was adequate to assess tumor viability after pre-operative radiotherapy in soft tissue sarcoma. MATERIAL AND METHODS: Post-contrast MR imaging of 36 soft tissue sarcomas performed 0-54 days (median 13 days) after pre-operative radiotherapy, were retrospectively reviewed and compared to post-operative histopathology reports. The contrast enhancement of the tumor was visually graded as minor, moderate or extensive. From the post-operative histopathology reports, three types of tumor response to radiotherapy were defined: Poor, intermediate or good. The size of the tumors before and after radiation was compared. RESULTS: Even if most viable tumors enhanced more than non-viable tumors, there was major overlapping and significant contrast enhancement could be seen in tumors where histopathological examination revealed no viable tumor tissue. Based on histopathology, there were 12 good responders; 8 of these showed minor, 3 moderate and 1 extensive contrast enhancement on MR imaging. Sixteen tumors had an intermediate response; 3 showed minor, 8 moderate and 5 extensive enhancement. Eight tumors had poor response; none showed minor enhancement, 3 moderate and 5 extensive enhancement. Both increase and decrease in tumor size was seen in lesions with a good therapy response. CONCLUSION: Static post-contrast MR imaging cannot reliably assess tumor viability after pre-operative radiotherapy in soft tissue sarcoma. In tumors with no viable tumor tissue, moderate and extensive contrast enhancement can be seen.

Isoprenoid regulation of cell growth: identification of mevalonate-labelled compounds inducing DNA synthesis in human breast cancer cells depleted of serum and mevalonate.

Growth arrest induced by serum depletion and/or treatment with mevinolin (an inhibitor of mevalonate synthesis) in the human breast cancer cell line Hs578T was overcome by exogenous mevalonate, indicating that some product or metabolite of mevalonate may be involved in the mediation of serum-regulated growth of these cells. In the search for such compounds we first tested a variety of known end products of mevalonate with respect to their ability to counteract the inhibition of DNA synthesis caused by serum-free medium and mevinolin. Thereby high doses (10 micrograms/ml) of dolichol-20 were found to cause a partial counteraction. After straight-phase HPLC purification of endogenous lipids, isolated from 3H- or 14C-mevalonate-labelled Hs578T cultures, we found that non-sterol lipids co-eluting with dolichols efficiently induced DNA synthesis. After further purification with reverse-phase HPLC it was confirmed that virtually all of this effect was achieved by compounds(s) (seen as a single UV and radioactive peak) co-eluting with dolichol-20. Nanogram doses, at most, of this (these) compound(s) elicited a substantial stimulation of DNA synthesis. The lipid(s) also counteracted the inhibition by mevinolin of N-linked glycosylation, indicating that it (they) also interfere(s) with this processing. Since treatment with tunicamycin (an inhibitor of N-linked glycosylation) abolished this growth-stimulative effect, N-linked glycosylation seems to be a necessary event in the processes leading to lipid-induced initiation of DNA synthesis.

A cell cycle study of human mammary epithelial cells.

The growth regulation of human mammary epithelial cells (HMEC) cultured in a growth factor/hormone-enriched (e.g. EGF, insulin) medium with bovine pituitary extract as the only undefined supplement was studied. The doubling times of the cultures, in which the cells appear in colonies, was 55-72 h, and a considerable intercolonial heterogenecity in proliferative activity could be demonstrated. However, every colony, irrespective of the size of the growth fraction, comprised a sub-population of rapidly growing cells which had a mean generation time of approximately 22 h. When insulin was removed from the culture medium, HMEC proliferation was inhibited. This growth inhibition was shown to be a result of a cell cycle-specific block.

Mevalonate is essential for growth activation of human fibroblasts: evidence for a critical role of protein glycosylation in the prereplicative period.

Human diploid fibroblasts, arrested following serum or mevalonate depletion, were restimulated to a maximal rate of DNA synthesis within 24 h after the addition of serum or mevalonate, respectively. In both cases the initiation of DNA synthesis was preceded by a 12-h prereplicative phase. Upon the stimulation with serum there was a rapid increase in HMG-CoA reductase activity, reflecting an elevated formation of mevalonate, which reached its maximal value 4 h after serum replenishment. If this serum-induced increase in mevalonate synthesis was inhibited, the subsequent initiation of DNA synthesis was prevented. Serum stimulation also increased the level of N-linked glycosylation, an event that was dependent on the increase in HMG-CoA reductase activity. After treatment of the cells with tunicamycin, an inhibitor of N-linked glycosylation, they failed to enter the S-phase. However, an increased level of N-linked glycosylation was not required during the whole of the period after serum stimulation. Instead, it seemed to be of critical importance only during the mid stage of the prereplicative phase (i.e., 4-8 h after stimulation). Our data suggest that the N-linked glycosylation required for initiation of DNA synthesis is of high-molecular-weight (90-240 kDa) proteins. These high-molecular-weight glycoproteins may include growth factor receptors. Indirect evidence raises the possibility that the expression of growth factor receptors may play a regulatory role in the mevalonate-dependent growth activation of human fibroblasts.

Inhibition of N-linked glycosylation down-regulates insulin-like growth factor-1 receptor at the cell surface and kills Ewing's sarcoma cells: therapeutic implications.

The insulin-like growth factor-1 receptor (IGF-1R) has been shown to be of critical importance for tumor development and tumor cell survival of various types of malignancies. We have previously demonstrated that an adequate N-linked glycosylation of IGF-1R is required for its translocation to the cell surface in melanoma cells. This raises the possibility of using glycosylation inhibitors as therapeutic agents against IGF-1R-dependent malignancies. In this study we show that inhibition of N-linked glycosylation using tunicamycin or the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor lovastatin resulted in down-regulation of IGF-1R at the cell surface in Ewing's sarcoma cell lines (RD-ES and ES-1 cells). The down-regulation of plasma membrane-bound IGF-1R was correlated with a drastic decrease in IGF-1R autophosphorylation, suggesting biochemical inactivation of the receptor. Whereas RD-ES and ES-1 cells responded differently with regard to DNA synthesis, the decrease in IGF-1R expression was accompanied by a rapid and substantial decrease in survival of both cell lines. Our data suggest that relatively untoxic HMG-CoA reductase inhibitors (e.g. lovastatin) could have therapeutic significance in IGF-1R-dependent neoplasms like Ewing's sarcoma.