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Summary The molecular basis of sarcoidosis phenotype heterogeneity and its relationship to effective treatment of sarcoidosis have not been elucidated. Peripheral samples from sarcoidosis subjects who participated in a Phase II study of golimumab [anti-tumour necrosis factor (TNF)-α] and ustekinumab [anti-interleukin (IL)−12p40] were used to measure the whole blood transcriptome and levels of serum proteins. Differential gene and protein expression analyses were used to explore the molecular differences between sarcoidosis phenotypes as defined by extent of organ involvement. The same data were also used in conjunction with an enrichment algorithm to identify gene expression changes associated with treatment with study drugs compared to placebo. Our analyses revealed marked heterogeneity among the three sarcoidosis phenotypes included in the study cohort, including striking differences in enrichment of the interferon pathway. Conversely, enrichments of multiple pathways, including T cell receptor signalling, were similar among phenotypes. We also identify differences between treatment with golimumab and ustekinumab that may explain the differences in trends for clinical efficacy observed in the trial. We find that molecular heterogeneity is associated with sarcoidosis in a manner that may be related to the extent of organ involvement. These findings may help to explain the difficulty in identifying clinically efficacious sarcoidosis treatments and suggest hypotheses for improved therapeutic strategies.

Lung function is a major criterion used to assess asthma control. Fluctuation analyses can account for lung function history over time, and may provide an additional dimension to characterise control. The relationships between mean and fluctuations in lung function with asthma control, exacerbation and quality of life were studied in two independent data sets.Data from 132 adults with mild to moderate asthma and 159 adults with severe asthma were analysed separately. Fluctuations in twice-daily peak expiratory flow (PEF) over 6 months were measured by α, representing the strength of correlation with past lung function and potentially asthma stability. α and mean percentage predicted PEF (%predPEF) were plotted with and compared between patients grouped by asthma control defined by recent GINA (Global Initiative for Asthma) guidelines, the Asthma Control Questionnaire score, exacerbations and Asthma Quality of Life Questionnaire score. Associations of α and %predPEF with these outcomes were examined using multiple regression analyses.Both α and %predPEF differed with and were significantly associated with GINA-defined asthma control in both the mild to moderate and severe asthma groups. Only α was related to whether or not exacerbations occurred in mild to moderate asthma, while %predPEF was more significantly related than α in severe asthma. In those with severe asthma, only %predPEF was significantly related to Asthma Control Questionnaire and Asthma Quality of Life Questionnaire scores.Lung function history quantified by fluctuation analysis provides additional information to mean lung function, and may help characterise the current state of asthma control. It may also potentially aid in phenotyping clinical asthma.

Rationale The treatment effect of golimumab, a human monoclonal antibody against tumor necrosis factor (TNF)-alpha, in severe persistent asthma is unknown. Objectives To assess the safety and efficacy of golimumab in a large population of patients with uncontrolled, severe persistent asthma. Methods From 2004 to 2006, 309 patients with severe and uncontrolled asthma, despite high-dose inhaled corticosteroids and long-acting beta(2) agonists, were randomized 1:1:1:1 to monthly subcutaneous injections of placebo or golimumab (50, 100, or 200 mg) through Week 52. Coprimary endpoints were the change from baseline through Week 24 in prebronchodilator percent-predicted FEV(1) and the number of severe asthma exacerbations through Week 24. Measurements and main results No significant differences were observed for the change in percent-predicted FEV1 (least squares mean: placebo, 2.44 [95% confidence interval (CI) -0.574 to 5.461]; combined 100-mg and 200-mg, 2.91 [0.696-5.116]) or severe exacerbations (mean +/- SD: placebo, 0.5 +/- 1.07 vs. combined 100-mg and 200-mg 0.5 +/- 0.97) through week 24. Through Week 24, 2.6% of patients treated with placebo vs. 19.5% of those treated with golimumab discontinued the study agent, and 1.3% and 7.8% discontinued study participation, respectively. An unfavorable risk-benefit profile led to early discontinuation of study-agent administration after the Week-24 database lock. Through Week 76, 20.5% of patients treated with placebo and 30.3% of patients treated with golimumab experienced serious adverse events, with serious infections occurring more frequently in golimumab-treated patients. One death and all eight malignancies occurred in the active groups. Conclusions Overall, treatment with golimumab did not demonstrate a favorable risk-benefit profile in this study population of patients with severe persistent asthma. Clinical trial registered with www.clinicaltrials.gov (NCT00207740).

Chronic obstructive pulmonary disease (COPD) is a progressive, smoking-related, inflammatory lung disease in which tumor necrosis factor-alpha is overexpressed and has been suggested to play a pathogenic role.To determine if infliximab, an anti-TNF-alpha antibody, results in clinical benefit and has an acceptable safety profile in patients with moderate to severe COPD.In a multicenter, randomized, double-blind, placebo-controlled, parallel-group, dose-finding study, subjects with moderate to severe COPD received infliximab (3 mg/kg [n = 78] or 5 mg/kg [n = 79]) or placebo (n = 77) at Weeks 0, 2, 6, 12, 18, and 24. Efficacy, health status, and safety were assessed through Week 44.Infliximab was generally well tolerated, but showed no treatment benefit as measured by the primary endpoint, Chronic Respiratory Questionnaire total score. Similarly, there was no change in secondary measures, including prebronchodilator FEV(1), 6-min walk distance, SF-36 physical score, transition dyspnea index, or moderate-to-severe COPD exacerbations. Post hoc analysis revealed that subjects who were younger or cachectic showed improvement in the 6-min walk distance. Malignancies were diagnosed during the study in 9 of 157 infliximab-treated subjects versus 1 of 77 placebo-treated subjects. No opportunistic infections were observed, and there were no differences in the occurrence of antibiotic-requiring infections, although the incidence of pneumonia was higher in infliximab-treated subjects. No infection-related mortality was observed. Higher proportions of infliximab-treated subjects discontinued the study agent due to adverse events (20-27%) than did placebo-treated subjects (9%).Subjects with moderate to severe COPD did not benefit from treatment with infliximab. Although not statistically significant, more cases of cancer and pneumonia were observed in the infliximab-treated subjects. The impact of infliximab on malignancy risk in patients with COPD needs to be further elucidated.

Patient-reported outcome (PRO) measures have been developed to measure symptoms and other aspects of health-related quality of life.The Sarcoidosis Assessment Tool (SAT), a sarcoidosis-specific PRO, was administered in a lung and skin sarcoidosis treatment trial. We explored SAT performance characteristics and correlation with standard clinical measurements to validate it as a useful clinical sarcoidosis-specific PRO.The SAT analyses focused on baseline and Week 16 assessments. Besides the SAT, participants underwent clinical and physician assessments plus additional PROs that were used as anchor variables and were compared with the SAT. Reliability was evaluated by using Cronbach α coefficient. Spearman correlation coefficients were used to evaluate the association between SAT scores with clinical and other PRO measures. Changes between assessments in the clinical and PRO "anchor" variables were classified as improved, stable, or worsened. Mean differences between adjacent categories of the known groups and mean changes from the ability to detect change analyses were reviewed for appropriate clinically important difference estimates.Results from 173 patients were analyzed. Each SAT module reflected appropriate anchor variables at baseline and in terms of change. The Cronbach α for each of these modules was at least 0.87. In addition, we successfully established a clinically important difference range for each SAT module.We demonstrated that the SAT is a reliable and consistent sarcoidosis-specific PRO. It has excellent internal consistency and reliability. A range of clinically important differences has been established for the SAT modules. Clinical trial registered with www.clinicaltrials.gov (NCT 00955279).

Sarcoidosis is characterised by non-caseating granulomas that secrete pro-inflammatory cytokines, including interleukin (IL)-12, IL-23, and tumour necrosis factor (TNF)-α. Ustekinumab and golimumab are monoclonal antibodies that specifically inhibit IL-12/IL-23 and TNF-α, respectively.Patients with chronic pulmonary sarcoidosis (lung group) and/or skin sarcoidosis (skin group) received either 180 mg ustekinumab at week 0 followed by 90 mg every 8 weeks, 200 mg golimumab at week 0 followed by 100 mg every 4 weeks, or placebo. Patients underwent corticosteroid tapering between weeks 16 and 28. The primary end-point was week 16 change in percentage predicted forced vital capacity (ΔFVC % pred) in the lung group. Major secondary end-points were: week 28 for ΔFVC % pred, 6-min walking distance, St George's Respiratory Questionnaire (lung group), and Skin Physician Global Assessment response (skin group).At week 16, no significant differences were observed in ΔFVC % pred with ustekinumab (-0.15, p = 0.13) or golimumab (1.15, p = 0.54) compared with placebo (2.02). At week 28, there were no significant improvements in the major secondary end-points, although a nonsignificant numerically greater Skin Physician Global Assessment response was observed following golimumab treatment (53%) when compared with the placebo (30%). Serious adverse events were similar in all treatment groups.Although treatment was well tolerated, neither ustekinumab nor golimumab demonstrated efficacy in pulmonary sarcoidosis. However, trends towards improvement were observed with golimumab in some dermatological end-points.

Background Determination of future risk of exacerbations is a key issue in the management of asthma. We previously developed a method to calculate conditional probabilities (π) of future decreases in lung function by using the daily fluctuations in peak expiratory flow (PEF). Objective We aimed to extend calculation of π values to individual patients, validated by using electronically recorded data from 2 past clinical trials. Methods Twice-daily PEF data were analyzed from 78 patients with severe (study A) and 61 patients with poorly controlled (study B) asthma. For each patient, the π value was calculated from 5000 PEF data points simulated based on the correlation and distribution properties of observed PEF. Given an initial PEF, the π value was defined as the probability of a decrease in PEF to less than 80% of predicted value on 2 consecutive days within a month. These probabilities were then compared with actual occurrences of such events and clinically defined exacerbations within the following month. Results π Values were related to actual occurrences of decreases in PEF (adjusted R 2 > 0.800 for both studies). Every increase of 10% in π value was associated with an odds ratio of having a future exacerbation of 1.24 (95% CI, 1.07-1.43) for study A and 1.13 (95% CI, 1.02-1.26) for study B, with better sensitivity and specificity than clinic-measured FEV 1 . Conclusion These results from 2 independent datasets with differing asthmatic populations and differing exacerbation criteria provide support that clinically relevant quantification of individual future risk of exacerbations is possible.

Background Chronic obstructive pulmonary disease (COPD) is characterized by progressive worsening of airflow limitation associated with abnormally inflamed airways in older smokers. Despite correlative evidence for a role for tumor necrosis factor-alpha in the pathogenesis of COPD, the anti-tumor necrosis factor-alpha, infliximab did not show clinical efficacy in a double-blind, placebo-controlled, phase II clinical trial. This study sought to evaluate the systemic inflammatory profile associated with COPD and to assess the impact of tumor necrosis factor neutralization on systemic inflammation. Methods Serum samples (n = 234) from the phase II trial were collected at baseline and after 24 weeks of placebo or infliximab. Additionally, baseline serum samples were obtained from an independent COPD cohort (n = 160) and 2 healthy control cohorts (n = 50; n = 109). Serum concentrations of a broad panel of inflammation-associated analytes were measured using a 92-analyte multiplex assay. Results Twenty-five proteins were significantly elevated and 2 were decreased in COPD, including highly elevated CD40 ligand, brain-derived neurotrophic factor, epidermal growth factor, acute-phase proteins, and neutrophil-associated proteins. This profile was largely independent of smoking status, age, and clinical phenotype. The majority of these associations of serum analytes with COPD are novel findings. Increased serum creatine kinase-muscle/brain and myoglobin correlated modestly with decreased forced expiratory volume at 1 second, suggesting cardiac involvement. Infliximab did not affect this systemic inflammatory profile. Conclusions A robust systemic inflammatory profile was associated with COPD. This profile was generally independent of disease severity. Because anti-tumor necrosis factor-alpha did not influence systemic inflammation, how to control the underlying pathology beyond symptom suppression remains unclear. Trial Registration ClinicalTrials.gov, No.: NCT00056264.

Sera from U.S. patients with SLE, RA, and various malignancies, clinically normal individuals with sero-activity to HIV, AIDS, and from pregnant women were tested for the presence of anti-c-myc antibodies. In an ELISA using recombinant human c-myc protein as the antigen, no difference in mean antibody titer was generally detected in these sera when compared to normal controls. Only three malignancy sera (two myeloid leukemia and only one lymphoma) and two patients with AIDS-related lymphoma exhibited exceedingly higher levels of anti-c-myc antibody. However, significantly elevated anti-c-myc antibody levels were found among 20 patients with African Burkitt's lymphoma (Ghana) and 20 normal Ghanians, thus apparently reflecting an autoimmune phenomenon prevalent in the endemic region. These findings indicated that elevated levels of anti-c-myc antibodies are not a general characteristic of patients with diseases that have been associated with increased expression of c-myc.

Cyclic AMP functions as a negative regulator of cell proliferation in a variety of cell systems. We show here that the proliferation of normal and neoplastic B cells can be inhibited by high intracellular levels of cAMP. Thus forskolin treatment of the neoplastic B precursor cell line Reh induced a rapid increase in the cAMP level, which was followed by an accumulation of cells in the G0/G1 phase of the cell cycle over a period of 2-3 days. Similar inhibition of Reh cell proliferation after 3 days was observed whether forskolin was present continuously or only during the first 5 hr. Both c-myc and c-Ha-ras protein levels were transiently down-regulated at 4 hr of forskolin treatment, suggesting that these protooncogenes play a role in the process leading to cAMP-mediated growth cessation. Northern-blot analysis showed that the steady-state levels of c-myc RNA rapidly declined in all phases of the cell cycle, to return to control levels within a time period of 24 hr. In contrast, the c-Ha-ras mRNA level was steadily maintained. Thus the expression of c-myc and c-Ha-ras protein was regulated at different metabolic levels. The reduced proliferative capacity of the B precursor cell line in the presence of forskolin was not linked to induced differentiation. This was judged from the lack of appearance of three different B cell differentiation markers; cytoplasmic immunoglobulin heavy chain and two antigens recognized by the monoclonal antibodies B1 (CD20) and HH1 (CD37). We also showed that forskolin partially inhibited the proliferation of normal B lymphocytes stimulated by anti-immunoglobulins (anti-mu) and B cell growth factor (BCGF). The burst of c-myc mRNA during activation of normal B cells was also reduced by forskolin.

The expression of the proto-oncogene c-myc was studied at the protein level in cells obtained from patients with AML and CML. In florid AML and during the blastic phase of CML the majority of cells contain c-myc protein with the amount of protein differing widely among the cells of individual patients. In contrast, during complete remission in AML and during the chronic phase of CML cells containing c-myc protein are rare. Several studies demonstrated a discordance in the amount of c-myc transcript and the amount of c-myc protein present in cell populations thereby suggesting the presence of translational or post-translational regulation of c-myc expression. Further, the data suggest that high levels of c-myc protein in the leukemic cells of AML patients are associated with a poor response to therapy and that high levels in AML patients in CR or in the peripheral blood of chronic phase CML patients may be indicative of impending acute leukemia.

We have analyzed c-myc protein expression during the cell cycle in malignant B-cell lymphomas by dual flow cytometric detection of a fluoresceinated polyclonal anti-myc antibody and propidium iodide which binds stochiometrically to DNA. The data obtained were correlated to other parameters of cell activation such as histopathological grading, expression of the activation antigen 4F2, light scatter (proportional to cellular volume), DNA synthesis and percentage of S-phase cells. The c-myc protein level was strongly correlated to parameters of DNA synthesis/content. In addition, the oncoprotein level was largely unvarying from the late G1 phase through the rest of the cell cycle in both malignant cells and normal purified B cells stimulated to proliferate in vitro.

We have investigated whether the translocated and the untranslocated human c-myc oncogenes of Burkitt lymphoma cells are equally or differentially expressed in host mouse B cells. The human c-myc mRNA levels in somatic cell hybrids between mouse plasmacytoma cells and Burkitt lymphoma cells with either the t(8;14) or the t(2;8) chromosome translocation were determined by using the nuclease S1 protection procedure. Although both the human parental lines and the hybrid cells carrying the translocated c-muc oncogene expressed high levels of human specific c-myc transcripts, the hybrid cells carrying the untranslocated c-myc gene on normal chromosome 8 did not contain human specific c-myc mRNA. These results suggest that the translocated human c-myc oncogene has escaped the normal transcriptional control to which the untranslocated c-myc gene remains subjected. This interpretation is also supported by the finding that the expression of the c-myc genes of lymphoblastoid cells and of HL-60 promyelocytic leukemia cells are repressed when they are transferred into a mouse plasmacytoma background. The ability of the translocated c-myc oncogene to escape the normal transcriptional control occurring in B cells may be important for the expression of B cell neoplasia in mouse and man. We have also transferred the Burkitt 14q+ chromosome carrying a translocated c-myc oncogene into mouse LM-TK- fibroblasts and studied the levels of human c-myc transcripts in the hybrids. Because the levels of human c-myc transcripts in the fibroblast hybrids are dramatically decreased in comparison to the plasmacytoma hybrids, we conclude that the levels of transcripts of the translocated c-myc oncogene depend on the differentiated state of the cells harboring the translocated chromosome.

Initiation of T-lymphocyte proliferation by mitogen or antigen involves a cascade of gene activation events. Thus, by the time mitogen-activated T cells have reached the G1/S interface, many genes that are transcriptionally silent in GO, like the c-myc, IL-2, IL-2 receptor (IL-2R) and transferrin receptor (TfR) genes, have been transcriptionally activated1–4. To understand the role of the individual genes in the activation process, one must be able to interfere specifically with the expression or function of each particular gene product. In this way, by blocking the IL-2R with an antibody, it has been demonstrated that IL-2/IL-2R interaction is required to induce TfR expression in activated T cells3. When the function or expression of intracellular proteins is to be blocked, however, the need to introduce antibodies into the cytoplasm of viable cells, although possible5–7, is a limiting factor. We have taken another approach, namely the exogenous addition to bulk cell cultures of small antisense oligomers. Sequence-specific anti-sense oligodeoxyribonucleotides have been reported to inhibit intracellular viral replication without interfering with cellular protein synthesis8,9. Similarly, rabbit globin mRNA translation in a cell-free system and in rabbit reticulocytes has been inhibited by oligomers complementary to the globin mRNA initiation codon region10. Recently, a pentadecadeoxyribonucleotide complementary to the initiation codon and four downstream codons of human c-myc mRNA was reported to inhibit the proliferation of the human leukaemic cell line HL-60 specifically11. We report here that the same c-myc complementary oligonuelectide inhibits mitogen-induced c-myc protein expression in human T lymphocytes and prevents S phase entry. Interestingly, c-myc antisense treatment did not inhibit G0 to G1 traversal as assessed by morphologic blast transformation, transcriptional activation of the IL-2R and TfR genes, or induction of 3H-uridine incorporation.

While a number of oncogenes are expressed in a cell cycle-dependent manner, their role in the control of cell proliferation can only be established by a direct functional assay. The c-myc protein, upon microinjection into nuclei of quiescent Swiss 3T3 cells, cooperated with platelet-poor plasma in the stimulation of cellular DNA synthesis. This suggests that c-myc protein, like platelet-derived growth factor (PDGF), may act as a competence factor in the cell cycle to promote the progression of cells to S phase. The presence in the medium of an antibody against PDGF abolished DNA synthesis induced by microinjected PDGF; however, the microinjected c-myc protein stimulated DNA synthesis even when its own antibody was present in the medium. The c-myc protein may act as an intracellular competence factor, while PDGF expresses its biological activity only from outside the cells.

The close link between an actively expressed c-myc gene locus and cellular proliferation has been established in a variety of cell types. By using normal human peripheral blood B cells as a model for in vivo quiescence, we have assessed the expression pattern of the c-myc gene in terms of transcriptional activation and concurrent production of c-myc protein, following induction by antibodies directed against antigens on the cell membrane. Both the 1F5 monoclonal antibody, which reacts with the pan B cell antigen CD20, and the anti-μ could promote transcriptional activation of the c-myc gene roughly corresponding to the increased levels of cytoplasmic c-myc mRNAs. In addition, more than 80% of the B cells could be induced to express c-myc protein by either stimulus. Since treatment only with polyclonal anti-μ renders the B cells competent to proliferate in the presence of BCGF, c-myc protein expression is not per se sufficient for cell cycle progression into S phase.

The nucleotide sequence of a clone containing mouse carbonic anhydrase (CA) cDNA in pBR322 has been determined. The cloned cDNA contains all of the coding region except for nucleotides specifying the first eight amino acids, and all of the 3' noncoding region, which consists of 700 nucleotides. A cDNA clone was identified which contains an additional 54 by at the 5' end, so that the complete amino acid sequence of mouse CA could be deduced. This sequence showed a 73–81 % homology with other mammalian CA form II isozymes, 56–63 with form I isozymes, and 52–56 % with form III isozymes. By examination of the amino acids which are unique and invariant for each isozyme, the mouse amino acid sequence was found to contain 16 of the 23 residues that are unique and invariant to mammalian CA form II isozymes, but only one or no residue for forms I and III, respectively.

Like other transforming genes of retro viruses, the v-myc gene of the avian virus, MC29, has a homologue in the genome of normal eukaryotic cells. The human cellular homologue, c-myc, located on human chromosome 8, region q24→qter (refs 1, 2), is translocated into the immunoglobulin heavy-chain locus on human chromosome 14 (ref. 3) in Burkitt's lymphoma1,4,5, suggesting that c-myc has a primary role in transformation of some human haematopoietic cells. In addition, c-myc is amplified in the human promyelocytic leukaemia cell line, HL60 (refs 6, 7) which also contains high levels of c-myc mRNA8. Recently, Colby et al.9 reported the nucleotide sequence of the human c-myc DNA isolated from a genomic recombinant DNA library derived from human fetal liver10. This 4,053-base pair (bp) sequence includes two exons and one intron of the myc gene, and the authors have suggested the existence of a human c-myc mRNA of 2,291 nucleotides that has a coding capacity for a protein of molecular weight (Mr) 48,812. We have approached the problem of accurately defining the characteristics of the human c-myc mRNA and c-myc protein by determining the sequence of the c-myc cDNA isolated from a cDNA library prepared from mRNA of a clone of the K562 human leukaemic cell line11. K562 cells are known to contain c-myc mRNA which is similar in size to the c-myc mRNA of other human cell types8. We report here the sequence of 2,121 nucleotides of a human c-myc mRNA and demonstrate that its 5′ noncoding sequence does not correspond to the sequence of the reported genomic human sequence. However, our data confirm that the intact human c-myc mRNA can encode a 48,812-Mr protein with a sequence identical to that reported by Colby et al.9.

NIARD (non-immunoglobulin-associated rearranging DNA) is located on mouse chromosome 15 at the break point of a commonly observed translocation event involving chromosomes 15 and 12 in murine plasmacytomas. The human cellular analogue of the v- myc oncogene of avian myelocytomatosis virus, strain MC-29, is known to reside on the distal end of human chromosome 8 and has been observed to translocate to chromosome 14 in Burkitt lymphomas. Using a cDNA clone specific for the transcript of the human c- myc gene (H c- myc ), we show that the mouse c- myc (M c- myc ) gene is contained within NIARD. NIARD-associated chromosome translocations occurred 1.3-2 kilobases (kb) 5′ of the mouse c- myc gene where NIARD recombines with the switch region of the C α immunoglobulin gene in various murine plasmacytomas. The mouse c- myc encoding region within NIARD spanned myc transcripts (i.e., ≈1.8-2.1 kb) were observed in plasmacytomas that have NIARD-associated chromosome translocations. Human c- myc and NIARD probes detected DNA rearrangements of human c- myc in four of seven Burkitt lymphomas. DNA sequences adjacent to the human c- myc gene recombined with the C μ immunoglobulin gene locus on chromosome 14 in several Burkitt lymphomas. The activation of the c- myc oncogene by chromosome translocation implicates its involvement in B-cell oncogenesis.

Specific chromosomal abnormalities have long been associated with various human and murine neoplasias (1–3). The most common chromosome defects consist of band deletions, reciprocal translocations and in some cases trisomy of a specific chromosome (1–3). Until recently, the molecular basis of these chromosomal rearrangements and the significance of their association with specific malignancies remained unknown. Cellular oncogenes (almost invariably found to be homologues of retroviral transforming genes) have been shown to exist in an activated form in a variety of human cancers. In the past year, a number of oncogenes have been localized to specific chromosome bands displaying abnormalities unique to specific neoplasias (2,3).

Comparative nucleotide sequence analysis of a rearranged c-myc gene in a murine plasmacytoma and c-myc cDNA from normal spleen reveals that chromosomal translocation in the plasmacytoma breaks the c-myc gene within the first exon or intron. In the plasmacytoma truncated c-myc RNAs initiate from newly exposed promoter sites. Nevertheless, the myc polypeptide produced in the plasmacytoma is probably the same as that from the intact c-myc gene because the exon lost by breakage and translocation is non-coding. The second and third exons of the mouse c-myc gene are substantially conserved in the v-myc gene of the avian retrovirus, MC29.

The myc oncogene has been implicated in the control of cellular proliferation in both normal and neoplastic cells. Recently, several cell lines have been shown to express c-myc mRNA and protein throughout the cell cycle (Thompson et al 1985; Hann et al 1985; Rabbitts et al 1985). However, in several cell systems triggering of quiescent cells into G1 is accompanied by a marked burst of c-myc mRNA, peaking a few hours after stimulation (Kelly et al 1983; Goustin et al 1985; Smeland et al 1985a). This has focused on a possible function for the c-myc product during the induction of competence to respond to progression growth factors acting in G1. This theory finds support in studies on fibroblast cell lines, where experimental manipulation of c-myc levels was related to cell cycle progression (Armelin et al 1984; Kaczmarek et al 1985). In both cases the increased myc levels provoked an increased sensitivity to the action of progression factors.

Both the human c-myc protooncogene and its avian retroviral counterpart, v-myc, have been associated with the malignant phenotype (Bishop 1983). In particular, alterations of the human c-myc gene, whether by translocation or amplification, have been associated with a wide range of human neoplasms (Yokota et al. 1986; Leder et al. 1983). Both proteins are known to be located in the cell nucleus and have been shown to bind to DNA in in vitro assays (Eisenman et al. 1985; Persson and Leder 1984; Watt et al. 1985). However the functions of the v- and c-myc proteins are still unknown.

The protein product of oncogene c-myc is believed to be important in regulation of the cell cycle. However, its direct role in DNA synthesis has not been explored. Experiments presented here show that the addition of affinity-purified antibodies against the human c-myc protein to nuclei isolated from several types of human cells reversibly inhibited DNA synthesis and DNA polymerase activity of these nuclei. This suggests that c-myc encodes a protein that is functionally involved in DNA synthesis.