Elevation of transforming growth factor alpha and its relationship to the epidermal growth factor and alpha-fetoprotein levels in patients with hepatocellular carcinoma.

A radioimmunoassay for transforming growth factor alpha (TGF-alpha) using synthetic rat sarcoma transforming growth factor and its rabbit polyclonal antibody has been developed. Using radioimmunoassays, the urinary TGF-alpha and epidermal growth factor (EGF) concentrations in 31 patients with hepatocellular carcinoma (HCC), 15 probable HCC, four metastatic liver cancer, and 33 age, sex-matched healthy controls were determined. For the first time, we have shown that the average TGF-alpha concentration for HCC patients was 21.5 +/- 20.3 micrograms per g creatinine, significantly higher than that of healthy subjects, 4.9 +/- 2.8 micrograms per g creatinine (P less than 0.001). There was no statistical difference in the level of EGF between HCC patients and controls (40.9 +/- 29.3 versus 46.2 +/- 16.6 micrograms per g creatinine; P greater than 0.05). The ratio of EGF/TGF-alpha between HCC patients (3.37 +/- 4.42) and controls (15.5 +/- 13.0) was significantly different (P less than 0.001). Among patients, 65% (20 of 31) of HCC cases and 87% (13 of 15) of probable HCC cases showed a marked elevation of TGF-alpha levels. We found only 16% (five of 31) of HCC cases with increased EGF level. EGF excretion was inversely age related. Serum total protein concentration and alkaline phosphatase activity were positively correlated to EGF concentration (r = 0.522, P less than 0.01 and rt = 0.393, P less than 0.05, respectively). There was no correlation between biochemical functions of liver and TGF-alpha concentration in HCC patients. Our results also suggested that TGF-alpha may be a useful complementary tumor marker for management of patients with clinical manifestation of HCC who have low alpha-fetoprotein levels.

HLA-DR-associated invariant chain is highly expressed in chronic lymphocytic leukemia.

Total RNA extracted from peripheral blood lymphocytes of a patient with B-cell chronic lymphocytic leukemia (CLL) and the poly (A+) RNA was purified. A cDNA library was constructed and approximately 4,000 clones were screened in order to identify genes preferentially expressed in CLL. A relatively low repetition frequency characterizes the majority of the abundant mRNA species present in CLL lymphocytes. One clone, corresponding to the mRNA encoding the HLA-DR-associated invariant chain, was selected and its expression was examined in different leukemic cell populations and in normal tissues. DNA-RNA hybridization studies showed that the invariant chain mRNA (In-mRNA) is detectable in RNA preparations from human blood cells and their precursors, whereas no In-mRNA is found in several other tissues examined. Among various normal and leukemic leukocyte populations, the highest levels of In-mRNA are found in CLL. Therefore, a role of In-chain mRNA as a marker of CLL is proposed. Our data support a relationship between high levels of invariant chain mRNA and the out of cycle condition of CLL peripheral blood lymphocytes.

Preferentially expressed genes in chronic myelogenous leukemia.

The predominant circulating cells in chronic myelogenous leukemia (CML) morphologically resemble normal myeloid precursors; however, certain characteristics indicate the two are not identical. Approximately 88% of the patients with clinically typical CML present with a cytogenetic abnormality known as the Philadelphia chromosome (Ph1). Additionally, the leukocyte alkaline phosphatase (LAP) value is decreased in CML. To investigate if there are selected genes expressed in the CML cell population, poly(A+)RNA from a chronic-phase, Ph1-positive CML patient was used for construction of a complementary DNA (cDNA) library. Recombinant clones representing moderately to abundantly transcribed sequences were selected by annealing [32P]-cDNA transcribed from homologous RNA to the library sequences and assessing radioactivity in the hybrids. From an initial 729 colonies, 417 (57.2%) displayed a hybridization signal more intense than controls, indicating these recombinant plasmids contained sequences homologous to moderately or highly expressed RNAs from this particular patient. Screening of the 417 clones--utilizing 32P-cDNAs derived from normal human placenta, an acute myelomonocytic leukemia (AMML), and two other CML samples--was used to select clones likely to represent sequences preferentially expressed in CML. Sixteen recombinants were initially selected that repeatedly failed to display hybridization with the placenta and AMML-derived probes. Further analysis of eight of these clones indicated that six contain sequences preferentially expressed in CML. One clone, C-A3, has been studied with 63 different RNA samples. This sequence is found to be highly expressed in peripheral blood cells from the chronic phase of both Ph1-positive and Ph1-negative CML as well as in a Ph1-positive acute myelogenous leukemia (AML). Expression is reduced in lymphoblastic crisis of CML (L BC-CML) and essentially absent in myeloblastic crisis of CML (M BC-CML). While preliminary, the results suggest that this probe may be useful as an aid in diagnosing Ph1-negative CML and in distinguishing M BC-CML from L BC-CML and Ph1-positive AML.

Differential mitogenic effects of methyl isobutyl xanthine and a tumor growth factor on G1-arrested 3T3 T proadipocytes at the predifferentiation GD state and the growth-factor deficiency GS state.

Two growth-states exist in the G1 phase of the 3T3 T proadipocyte cell cycle. GD is the arrest state at which proadipocytes must growth-arrest prior to differentiation. GS is the arrest state at which proadipocytes growth-arrest following deprivation of serum or growth factors. In an attempt to further distinguish these arrest states, we have compared the relative ability of a variety of mitogens to induce GD- and GS-arrested cells to initiate DNA synthesis. The data show that GD-arrested cells at both high and low densities can be induced to proliferate by methyl-isobutyl-xanthine (MIX), whereas high and low density GS-arrested cells are not. The data also show that a tumor growth factor can stimulate the proliferation of both high and low density GD- and GS-arrested cells, whereas other agents are poor mitogens for high density GD-arrested cells. We conclude that MIX and a tumor growth factor (TUGF) can serve as probes to study the characteristics of the GD arrest state.

Efficient extraction of RNA from mammalian tissue.

RNA extraction from mammalian tissue has been compared using the different deproteinizing agents: a) guanidine-HCl, b) guanidinium-thiocyanate, c) buffer-saturated phenol, or d) buffer-saturated phenol followed by a proteinase K digestion of the aqueous phase. Both solid tissues (first, second, and third trimester fetal bovine pancreas), and human white blood cell populations were studied. Degradation, as seen in citric acid-urea agarose gels, and the ability to serve as templates for cell-free protein synthesis were used as criteria to assess the efficiency of the different methods. We conclude that employing buffer-saturated phenol with proteinase K digestion is a superior method for consistent extraction of relatively undegraded RNA in quantitative amounts from mammalian tissue.

Coupling of proadipocyte growth arrest and differentiation. II. A cell cycle model for the physiological control of cell proliferation.

Experimental evidence is presented that supports a cell cycle model showing that there are five distinct biological processes involved in proadipocyte differentiation. These include: (a) growth arrest at a distinct state in the G1 phase of the cell cycle; (b) nonterminal differentiation; (c) terminal differentiation; (d) loss of the differentiated phenotype; and (e) reinitiation of cell proliferation. Each of these events is shown to be regulated by specific human plasma components or other physiological factors. At two states designated GD and GD', coupling of growth arrest and differentiation is shown to occur. We propose that these mechanisms for the coupling of growth arrest and differentiation are physiologically significant and mimic the regulatory processes that control stem cell proliferation in vivo.

Cell cycle models for the aberrant coupling of growth arrest and differentiation in hyperplasia, metaplasia, and neoplasia.

The control of cell proliferation can be regulated by the coupling of growth arrest and differentiation. Since this process has been demonstrated both in vivo and in vitro, it is thought to be of considerable physiologic significance. The mechanisms that serve to couple growth arrest and differentiation were, however, poorly defined prior to our recent studies. We established that the coupling of growth arrest and differentiation of proadipocytes occurs at a distinct state in the G1 phase of the cell cycle, GD, and that it consists of at least five phases. These include: 1) growth arrest at GD; 2) nonterminal differentiation; 3) terminal differentiation; 4) loss of the differentiated phenotype, and 5) reinitiation of cell proliferation. On the basis of these observations we developed a cell cycle model to explain the biologic mechanisms of the coupling process. This model is now used to predict where defects in the coupling of growth arrest and differentiation may occur in hyperplastic, metaplastic, and neoplastic cells.

Growth arrest of proadipocytes at a distinct predifferentiation G1 state associated with cytotoxic responsiveness to 8-bromo cyclic AMP.

The control of cell proliferation can result from the coupling of growth arrest and differentiation. In this regard, we recently demonstrated that growth arrest which precedes the differentiation of 3T3 T proadipocytes must occur at a distinct state in the G1 phase of the cell cycle (GD). Cells arrested at GD differ in several biological parameters from cells arrested in G1 at other states induced by either serum deprivation (GS) or nutrient deficiency (GN). Specifically, GD-arrested cells can differentiate in the absence of DNA synthesis and GD-arrested cells can be induced to proliferate when stimulated with 1-methyl-3-isobutylxanthine; GS- and GN-arrested cells cannot. In addition, GD-, GS- and GN-arrested cells reside at topographically distinct states in G1. We now report that GD-arrested proadipocytes are also distinct in that they are highly sensitive to a cytotoxic effect of 8-bromocyclic AMP, whereas GS- and GN-arrested cells are not.

Coupling of growth arrest and differentiation at a distinct state in the G1 phase of the cell cycle: GD.

The differentiation of most mammalian cells is preceded by growth arrest in the G1 phase of the cell cycle, but the characteristics of this state have not been established. We now report that the growth arrest that precedes the differentiation of BALB/c 3T3 T mouse proadipocytes must occur at a distinct state in G1 designated GD. GD-arrested cells are characterized by their ability to differentiate in the absence of DNA synthesis and by their unique sensitivity to the mitogenic effect of isobutylmethylxanthine. Proadipocytes induced to become G1 growth arrested at other states by culture in medium deficient in growth factor or nutrients, by contrast, are unable to differentiate in the absence of DNA synthesis and are not stimulated to proliferate by isobutylmethylxanthine even when they are exposed to differentiation-promoting medium prior to arrest. These data support the conclusion that, prior to the expression of a differentiated phenotype, proadipocytes must arrest their growth at a distinct state in the G1 phase of the cell cycle, GD. These data also provide the basis for the hypothesis that carcinogenesis is associated with defects in the coupling of growth arrest and differentiation at the GD state.

Differentiation of fibroblast-like cells into macrophages.

Differentiated cells with the morphological, enzymatic, antigenic, and functional characteristics of macrophages formed when a variety of nontransformed and transformed fibroblast-like mouse embryo cell lines were grown in a medium supplemented only with human plasma. Differentiated cells contained numerous lysosomes and phagosomes, nonspecific esterase and acid phosphatase activities, and cell surface la antigens and were capable of phagocytosis of iron particles. Differentiated cells were also growth arrested in the G1 phase of the cell cycle, but both growth arrest and differentiation were reversible processes. These observations suggest that cells with the morphology of fibroblasts have the capacity to undergo nonterminal differentiation into macrophages.

Regulation of endogenous murine leukemia virus-related nuclear and cytoplasmic RNA complexity in C57BL/6J mice of increasing age.

The nucleotide sequence complexity of murine leukemia virus *MuLV)-related RNA has been measured by RNA-complementary DNA hybridization analysis in nuclear and cytoplasmic RNA isolated from liver and brain of low-leukemia-strain C57BL/6J mice of different ages. In these two tissues, an approximate 1.5- to 2-fold increase in the complexity of steadystate nuclear MuLV-related RNA sequences was observed as a function of age. Maximum complexity was observed with nuclear RNA extracts from old mice and corresponded to roughly 70 to 75% of the total MuLV genome. In contrast to the age-related increase in complexity of nuclear MuLV genome was detected in liver and brain steady-state cytoplasmic RNA, irrespective of animal age. These data suggest that control mechanisms regulating the transcription and/or stabilization of nuclear RNA transcripts of endogenous mouse MuLV-related genomes become less stringent with animal age even in low-tumor mouse strains. The data also support the existence of independent posttranscriptional mechanisms which prevent accumulation of these MuLV-related transcripts in steady-state cytoplasmic RNA and which do not seem to be as subject to the relaxation of stringency as a function of age.