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Background: Cancer is one of the leading worldwide causes of death. It may be induced by a variety of factors, including carcinogens, radiation, genetic factors, or DNA and RNA viruses. The early detection of cancer is critical for its successful therapy, which can result in complete recovery from some types of cancer., Methods: Raman spectroscopy has been widely used in medicine and biology. It is a noninvasive, nondestructive, and water-insensitive technique that can detect changes in cells and tissues that are caused by different disorders, such as cancer. In this study, Raman spectroscopy was used for the identification and characterization of murine fibroblast cell lines (NIH/3T3) and malignant fibroblast cells transformed by murine sarcoma virus (NIH-MuSV) cells., Results: Using principal component analysis and LDA it was possible to differentiate between the NIH/3T3 and NIH-MuSV cells with an 80-85% success rate based on their Raman shift spectra., Conclusions: The best results for differentiation were achieved from spectra that were obtained from the rich membrane sites., General Significance: Because of its homogeneity and complete control of most factors affecting its growth, cell culture is a preferred model for the detection and identification of specific biomarkers related to cancer transformation or other cellular modifications.

Fourier transform infrared microspectroscopy (FTIR-MSP) is potentially a powerful analytical method for identifying the spectral properties of biological activity in cells. The goal of the present research is the implementation of FTIR-MSP to study early spectral changes accompanying malignant transformation of cells. As a model system, cells in culture are infected by the murine sarcoma virus (MuSV), which induces malignant transformation. The spectral measurements are taken at various postinfection time intervals. To follow up systematically the progress of the spectral changes at early stages of cell transformation, it is essential first to determine and validate consistent and significant spectral parameters (biomarkers), which can evidently discriminate between normal and cancerous cells. Early stages of cell transformation are classified by an array of spectral biomarkers utilizing cluster analysis and discriminant classification function techniques. The classifications indicate that the first spectral changes are detectable much earlier than the first morphological signs of cell transformation. Our results point out that the first spectral signs of malignant transformation are observed on the first and third day of postinfection (PI) (for NIH/3T3 and MEF cell cultures, respectively), while the first visible morphological alterations are observed only on the third and seventh day, respectively. These results strongly support the potential of developing FTIR microspectroscopy as a simple, reagent-free method for early detection of malignancy.

An aqueous extract of propolis was found to significantly inhibit NIH/3T3 cell malignant transformation by Moloney murine sarcoma virus (MuSV-124). The inhibitory effect of propolis extract was most effective when it was added 2 h before infection or at the time of infection. The continuous presence of propolis extract in the culture medium was essential for full prevention of malignant cell transformation. When treatment with propolis extract was terminated, five to ten days post-infection, there was a significant recovery in cell transformation. These results suggest that propolis extract inhibits a late step after provirus integration into the host genome. Addition of propolis extract after infection with MuSV significantly inhibited cell transformation. The inhibitory effect of propolis appeared to be the result of the inhibition of primary--not secondary--infections, since MuSV-124 yields a virus-nonproducing infection.

In the present study we report on novel immunoregulatory functions lately attributed to fibroblasts, namely participation in cellular immune responses in connective tissues, by generation of pro-inflammatory cytokines and by presenting antigens to proliferating T cells. In order to execute immunoregulatory functions, the fibroblast has to be activated by signals abundant at inflammatory sites, i.e., cytokines and bacterial products. It was demonstrated that such immune-activated fibroblasts are able to generate a variety of cytokines such as interleukin-1 (IL-1), IL-6, colony stimulating factors (CSFs) as well as prostaglandins. The array of cytokines generated by immune-activated fibroblasts is determined by the stimulant and is controlled at multiple regulatory levels, such as transcription, translation, post-translational modifications, compartmentalization within the producing cell as well as the timing of expression. Some oncogene-transformed fibroblastoid cells lines were shown to constitutively generate IL-1 (and not IL-1 beta), as evidenced by the continuous expression of specific mRNA and biological activity of the cytokine, associated to the cell membrane or located in the cytosol. When these IL-2 producing cell lines were injected into mice, they failed to generate established tumors or regressed following initial growth, possibly due to mounting the host anti-tumor specific immune responses in which cytotoxic lymphocytes (CTLs) predominate. In contrast, IL-1 non-producing tumor cell lines induced progressive tumors which ultimately killed the animals. However, IL-1 non-producing fibroblastoid cell lines shifted from an in vivo progressive to a regressive phenotype, following immune activation of the malignant cells in vitro with cytokines/LPS. Similarly, primary immune-activated fibroblasts also induced tumor regression, mediated by anti-tumor specific immune responses, when the fibroblasts were injected into the vicinity of the tumor. Thus, the importance of activated stromal cells on tumor development was emphasized. This situation is relevant to the development of malignancies, as tumor growth is often accompanied by a local inflammatory response. Thus, the induction of IL-1 and other pro-inflammatory cytokines expression by the malignant cells or by stromal cells, in the vicinity of the tumor, might be efficient for tumor eradication. These findings should serve as a basis for development of novel immunotherapeutical strategies for the eradication of solid tumors.

In a previous study we have shown that a single infectious particle of Moloney murine leukaemia virus per cell is sufficient to facilitate chemical carcinogenesis in normal rat kidney cells. When these cells are exposed to the carcinogen after a low number of passages post-infection (p.i.), cell transformation becomes apparent only after many subsequent passages. On the other hand, when exposure is done after a high number of passages p.i., cell transformation can be detected in the treated culture or at the next passage. It is thus evident that whereas the carcinogenic effect is rapid, the viral effect becomes apparent only after a long period of latency. Here we provide evidence that this viral effect requires multiple proviruses and that the long latent period reflects the time needed for a sufficient accumulation of proviruses in some of the cells. This accumulation may result from multiple rounds of superinfection by virions released into the culture medium, although we cannot exclude other mechanisms of provirus amplification. Our data also suggest that this amplification enhances virus production.

We have examined interleukin-1 (IL-1) expression in a series of oncogene-transformed NIH-3T3 fibroblastoid cell lines. In contrast to primary fibroblasts where IL-1 is inducible, NIH-3T3 cells (clone 490N3T) transcribe the IL-1 alpha gene constitutively. Transformation of 490N3T cells by the v-mos or v-H-ras oncogenes appears to either enhance or suppress IL-1 alpha transcription, respectively. In v-myc transfected cells, constitutive IL-1 activity could be detected intracellularly. An additional membrane-associated form of IL-1 was observed in lines transformed by protein-kinase (PK) encoding oncogenes, such as TPR-met, c-met, v-src, v-abl, v-mos and v-raf. In none of the lines tested the secreted form of IL-1 activity could be detected, and no constitutive expression of IL-1 beta was observed. Our studies manifest aberrations in IL-1 expression in oncogene-transformed fibroblastoid cell lines, detected at different regulatory levels, such as transcription, translation and compartmentalization. IL-1 is a potent pleiotropic cytokine, with regard to its target cell specificity and spectrum of activities; growth promoting effects of IL-1 on fibroblasts were reported and on the other hand this cytokine activates various anti-tumor mechanisms. Thus, endogenous IL-1 expression by tumor cells may affect the neoplastic phenotype, either by influencing the growth of the malignant cells or by modifying tumor-host interactions.

We demonstrate in this study that infection with Moloney murine leukemia virus (M-MLV) and exposure to 3-methylcholanthrene (3-MC) can cooperate to transform NIH/3T3 mouse fibroblasts. M-MLV seems to stimulate the expression of c-myc and of a certain major histocompatibility complex (MHC) class I gene. Yet M-MLV infection by itself is insufficient to transform these cells. However, exposure of the infected cells to 3-MC resulted in a rapid cell transformation with concomitant enhancement of c-Ha-ras and H-2K class I MHC gene expression in the transformed cells. No such transformation was observed when uninfected NIH/3T3 cells were similarly treated with this carcinogen. Clones of cells transformed by this combined effect of M-MLV and 3-MC were found to be highly tumorigenic in fully immunocompetent allogeneic BALB/c mice. We provide evidence to suggest that the enhanced expression of the H-2K gene in these transformed cells plays an important role in overcoming the BALB/c allogeneic barrier and allowing tumor growth in these mice.

A series of wild-type and mutant raf genes was transfected into NIH 3T3 cells and analyzed for transforming activity. Full-length wild-type c-raf did not show transforming activity. Two types of mutations resulted in oncogenic activity similar to that of v-raf: truncation of the amino-terminal half of the protein and fusion of the full-length molecule to gag sequences. A lower level of activation was observed for a mutant with a tetrapeptide insertion mapping to conserved region 2 (CR2), a serine- and threonine-rich domain located 100 residues amino-terminal of the kinase domain. To determine essential structural features of the transforming region of raf, we analyzed point and deletion mutants of v-raf. Substitutions of Lys-56 modulated the transforming activity, whereas mutation of Lys-53, a putative ATP binding residue, abolished it. Deletion analysis established that the minimal transforming sequence coincided precisely with CR3, the conserved Raf kinase domain. Thus, oncogenic activation of the Raf kinase can be achieved by removal of CR1 and CR2 or by steric distortion and requires retention of an active kinase domain. These findings are consistent with a protein structure model for the nonstimulated enzyme in which the active site is buried within the protein.

The complete 606 amino acid sequence of the human A-raf oncogene has been deduced from the 2453 nucleotide sequence of a human T cell cDNA. A cysteine-rich region located near the amino terminus, which is highly conserved in A-raf and c-raf, shows significant homology with protein kinase C. A 5' deleted fragment of the cDNA has been incorporated into a murine retrovirus which endows the virus with the ability to transform cells in vivo and in vitro. Functionally, human A-raf is similar to v-raf and v-mos in that transformation is independent of ras gene function.

Foci of transformed cells, produced by MSV(124), appeared to result only from the primary infection, since this virus stock yielded a virus-nonproducing infection. On the other hand, the majority of foci scored in MSV/MLV-infected cultures, were generated by multiple secondary infections with the progenies of the primary infection. Mouse interferon (IF) was highly inhibitory for cell transformation by both virus stocks. However, this inhibition was apparent in MSV(124) infected cultures only if IF was added at least 12 h before infection, whereas in MSV/MLV-infected cultures IF was highly effective even if added 24 h after infection. The inhibition of focus formation by MSV(124) was irreversible after removal of IF, suggesting that IF inhibited an early step before provirus integration into the host genome. By contrast, in MSV/MLV-infected cultures focus formation was almost completely restored after recovery from the IF effect. Nevertheless, examination of virus production after IF removal proved that in MSV/MLV infection, too IF exerted and inhibitory effect before provirus integration.

raf oncogenes were shown to act synergistically with myc in transformation. The contribution of myc was identified as that of a "second messenger" in signal transduction of at least some, competence inducing, growth factors. The role of raf appears to be that of a cytosolic ser/thr specific protein kinase which was placed downstream of ras in the signal transduction of serum growth factors by ras and raf antibody microinjection experiments. Because of the inability of raf to abrogate a cells need for myc inducing competence factors, as well as its synergistic effect with myc, raf was placed downstream of ras in the progression pathway of cellular growth control. We speculate that the basis for synergism with myc might be the ability of raf to activate competence factor induced myc protein or a myc induced protein by phosphorylation. The role of raf in lung tumors was examined by the development of a high incidence mouse model system using ethylnitrosourea as carcinogen and butylated hydroxytoluene as promoter. raf proteins of normal size were expressed at high levels, raf protein vaccination was apparently effective in eliminating the promoted phase of tumor induction.

Normal rat kidney (NRK) cell were found to be resistant to neoplastic transformation by diverse carcinogenic chemicals. To study chemical-retroviral co-carcinogenesis in this cells they were infected with a low multiplicity of Moloney murine leukemia virus (M-MLV). Using a single cell cloning procedure, a virus-producing clone was isolated from the infected cells, which was shown to carry only one integrated M-MLV provirus per cell. It was found that this single provirus was sufficient to render the clone susceptible to transformation by 3-methylcholanthrene (3-MC). However this clone responded differently to the carcinogen at different passages after infection. When exposed to 3-MC at a low passage postinfection (passage 5), cell transformation was evident only after 11 subsequent subcultures. On the other hand when it was chemically treated at a high passage postinfection (passage 29), cell transformation could clearly be detected already at the next subculture after the chemical treatment. It is suggested that an M-MLV-mediated cumulative effect is necessary to complement the action of the carcinogen in order to complete the carcinogenic process in these cells. This cumulative viral effect appeared to be associated with a change in the control of the virus expression, since 3-MC was found to stimulate virus replication in this clone also only at the high passage postinfection. Indeed virus release by cells of isolated transformed foci, produced by the chemical-M-MLV co-carcinogenesis, was extremely higher than by untransformed cells.

The present study was carried out with a normal rat kidney cell clone that was initiated from a single cell infected by only one infectious particle of the non-transforming retrovirus, Moloney murine leukemia virus. Although the parental cells were highly resistant to chemical carcinogenesis, this infected clone was rendered susceptible to transformation by chemical carcinogens. However, when it was exposed to the tested carcinogen at a low subculture passage post-infection, cell transformation was detectable only after many subsequent passages. On the other hand, if it was exposed to the carcinogen at a high passage post-infection, cell transformation was detectable sometimes even without further passage, or in other cases after the first subsequent passage. Mouse interferon could inhibit the transformation by carcinogen employed at the low but not at the high passage post-infection. This inhibitory effect was reversible; if interferon was removed, even after the cells had been passaged many times in its presence, cell transformation became visible at passage 11 after interferon removal, although no treatment with the carcinogen was repeated. Interferon had no effect on the replication or the focus-forming capacity of cells transformed by such chemical-retroviral co-carcinogenesis. The possibility that this carcinogenic process depends on amplification of the integrated provirus DNA, and that this amplification can be inhibited by interferon is discussed.