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At least 19 recordsLinked to original sources
PubMed2026

Viral mimicry escape as a necessary feature of malignant transformation.

Malignant transformation is driven by disruption of pathways regulating proliferation and cell fate, but these same disruptions can create a collateral vulnerability: loss of transcriptional and epigenetic control over transposable elements and other normally silenced genomic regions. Consequently, emerging cancer cells can accumulate transposable element-derived and other endogenous immunogenic nucleic acids capable of triggering antiviral responses, a process termed viral mimicry. Increasing evidence indicates that viral mimicry can eliminate precancerous cells and shape tumour evolution, positioning it as an intrinsic tumour-suppressive mechanism. Here we highlight how cancer-associated changes in DNA methylation, histone modifications, splicing and RNA processing can lead to the presence of immunogenic nucleic acids that can activate viral mimicry pathways. We outline how cancer cells suppress viral mimicry, including compensatory epigenetic repression, RNA editing, nucleic acid decay and dampening of interferon signalling to enable cancer cell growth. Finally, we highlight the evidence suggesting that escaping viral mimicry is a fundamental process for cancer initiation and progression, and suggest that viral mimicry escape is necessary for cancer transformation and a therapeutic target in combination with immunotherapies. By framing viral mimicry escape as a necessary part of cancer transformation, this Review provides a unifying conceptual model for its translational exploitation.

Journal Article↗
PubMed1975

Plasma membrane alteration associated with malignant transformation in culture.

The intramembrane organization of the plasma membranes of nonmalignant cells in culture has been compared by freeze-fracturing with that of virally-transformed malignant cells. No dramatic differences are present in the distribution of intramembrane particles in the plasma membranes of these cells when the cells are examined without fixation or with mild fixation (glutaraldehyde treatment) prior to freezing. However, a redistribution of intramembrane particles into aggregates occurs in the membranes of nontransformed cells after treatment with glycerol. The aggregation of particles is extensive in normal chick embryo fibroblasts, and less extensive in mouse 3T3 cells. The glycerol-induced particle redistribution is not inhibited at 4 degrees, but it is inhibited by pretreatment with 2.5% glutaraldehyde. A significant number of the cells remain viable after the glycerol treatment, and the process is reversible. Particle aggregation does not appear to be related to either growth rate or cell density. Transformed Rous sarcoma virus/chick embryo fibroblasts and simian virus 40/3T3 cells have few particle aggregates after glycerol treatment. The plasma membranes of chick embryo fibroblasts transformed with a mutant of Rous sarcoma virus (TS-68) that is temperature sensitive for transformation, have few particle aggregates when grown at the permissive temperature (37 degrees). Extremely prominent particle aggregates are present in the plasma membranes of cells grown at the nonpermissive temperature (41 degrees). These observations indicate that there is an alteration in the plasma membrane associated with viral transformation which is related to a glycerol-sensitive mechanism that controls the distribution of intramembrane particles.

Animals↗
PubMed1979

Qualitative changes in the biologic characteristics of cultured fetal rat keratinizing epidermal cells during the process of malignant transformation after benzo[a]pyrene treatment.

In vitro malignant transformation of fetal rat keratinizing epidermal cells from inbred SD rats after benzo[a]pyrene (BP) treatment was analyzed from various biologic viewpoints. BP treatment directly and indirectly effected changes in cell growth characteristics, i.e., temperature dependence for growth, in vitro keratinization, chromosome structure, and the ability to form colonies on plastic substrate, on 0.57% agar medium layer, and in 0.33% soft agar medium. BP-treated cells at 30 degrees C remained in the premalignant stages and showed shifts in chromosome structure toward the hypodiploid range and parakeratotic changes in their keratinization process. However, the cells failed to form colonies even on a plastic substrate. BP-treated cell lines that adapted to temperatures of 35 and 37.5 degrees C remained in the premalignant stages; however, they acquired the ability to form colonies on plastic substrates during subcultivation. Malignantly transformed colonies appeared in these cell lines. In vitro keratinization processes were classified into nearly normal (diffuse lamellar, focal lamellar, and parakeratotic), intermediate, and atypical subtypes (columnar, spherical, and single-cell type). Cells of atypical keratinization subtypes and some of the intermediate subtypes formed squamous cell carcinomas in syngeneic hosts. Malignantly transformed cells showed shifts in chromosome structure toward the hypotetraploid range and colony formation on the 0.57% agar medium layer. However, they failed to form colonies in 0.33% soft agar medium. With the use of changes in biologic characteristics of the cells as indicators, fetal rat keratinizing epidermal cells in culture were classified into five stages. The appearance of stage III cells seemed to be the first key step in their malignant transformation.

Animals↗
PubMed2026

Tissue-based genomic instability markers for predicting malignant transformation in oral leukoplakia and proliferative verrucous leukoplakia: a systematic review.

OBJECTIVES: Although several biomarkers have been described for predicting malignant transformation in oral leukoplakias (OLs) and proliferative verrucous leukoplakias (PVLs), no systematic review has comprehensively evaluated tissue-based genomic instability markers. This review aimed to evaluate the evidence for these markers and their potential role in biomarker panel development. METHODS: A systematic review across PubMed, Embase and Cochrane Library was performed to identify studies evaluating the differences in tissue-based genomic markers between OL and PVL patients with and without malignant transformation. RESULTS: 34 observational studies comprising 3,237 patients were included, and genomic aberrations were categorised into DNA-level, chromosomal, and gene-specific alterations. For studies on OLs, DNA-level and chromosomal markers for which individual studies reported associations with malignant transformation included aneuploidy, impaired DNA repair capacity, loss of heterozygosity, chromosomal instability, and copy number alterations. Multiple gene-specific alterations also showed associations (e.g., TP53, MKI67, FGFR1), but findings varied across studies. The genomic markers of PVLs differed substantially, with fewer consistent predictors found. No meta-analysis was performed as all included studies were observational. CONCLUSIONS: Genomic instability across multiple levels contributes to malignant transformation, and represents a promising biological framework for predicting malignant transformation for OLs. While no single marker reliably demonstrates sufficient predictive performance, the integration of complementary genomic alterations with clinical and histopathological risk factors may provide a basis for the development of robust multi-marker panels. Future prospective studies using standardised detection methods and multivariable prediction models are required before clinical implementation. SYSTEMATIC REVIEW REGISTRATION: identifier CRD42024585830.

carcinoma↗
PubMed1979

Increased susceptibility of mouse cells to fluorescent light-induced chromosome damage after long-term culture and malignant transformation.

Exposure of mouse cells in culture to fluorescent light has been shown to produce chromatid breaks and exchanges. Hydrogen peroxide formed in the cell during illumination has been implicated as the causative agent. The present results indicate that susceptibility to light-induced chromosome damage increases with time in culture and seems to be associated with or requisite for the spontaneous malignant transformation of mouse cells. All three cell lines followed during long-term culture that either became tumorigenic or showed cytological evidence of neoplastic transformation developed a concomitant increase in susceptibility. In three additional cell lines, susceptibility to light-induced chromatid damage was significantly increased in the spontaneously transformed malignant cells as compared with their nonneoplastic precursors. The increased susceptibility is not simply the result of long-term culture, since three other nonneoplastic cell lines after prolonged culture were significantly less susceptible than their malignant counterparts. Increased susceptibility to light-induced chromatid damage could result from impaired DNA repair or from the loss of defense mechanisms for destroying H2O2 or scavenging free radicals.

Animals↗
PubMed2026

Establishing a genetic mutation panel for predicting malignant transformation of oral leukoplakia: A prospective cohort study.

OBJECTIVE: To investigate somatic mutations in the whole genes of tissue samples from patients with oral leukoplakia (OLK), as the most typical precursor of oral cancer; and identify the specific genes as a mutational panel for predicting OLK malignant transformation. METHODS: A total of 123 consecutive OLK patients with long-term follow-up (median, 73&#xa0;months) were prospectively enrolled, and divided into training set (n&#xa0;=&#xa0;92) and independent test set (n&#xa0;=&#xa0;31) based on chronological order of enrollment. Genomic DNA was isolated from the fresh-frozen biopsy tissues and somatic mutations in all genes were measured by whole-exome sequencing. RESULTS: We constructed a 3-gene (TP53, CASP8, and CYP2B6) mutational panel for risk stratification (any mutation vs. no mutation) of OLK malignant transformation. Kaplan-Meier analysis showed that the prognostic power of the 3-gene panel (log-rank P&#xa0;<&#xa0;0.0001) for risk stratification in malignant progression was better than that of pathological grade in the training and test set, respectively. Multivariate Cox regression analysis revealed that this panel was an independent variable significantly associated with progression in the training (hazard ratio [HR]&#xa0;=&#xa0;8.05; P&#xa0;<&#xa0;0.001) and test set (HR&#xa0;=&#xa0;11.26; P&#xa0;=&#xa0;0.0421), respectively. The area under the curve (AUC) with 95&#xa0;% confidence interval was 0.770 (0.648-0.892) and 0.877 (0.705-1.000) in the training and test set, respectively, for predicting malignant transformation in OLK patients. CONCLUSIONS: We established a 3-gene (TP53, CASP8, and CYP2B6) mutational panel as risk stratification model could effectively predict OLK malignant transformation, outperforming pathological grading-based assessment. Such genetic markers may provide a foundation for developing personalized management strategies.

Humans↗
PubMed1977

Malignant transformation of ameloblastic fibro-odontoma to ameloblastic fibrosarcoma.

Two cases of malignant transformation of ameloblastic fibro-odontomas are presented, along with a review of the literature on ameloblastic fibrosarcomas. The occurrence of this malignant transformation of ameloblastic fibromas, ameloblastic odontomas, and ameloblastic fibro-odontomas appears to be more frequent than previously thought. This potential transformation alone does not justify radical treatment of all these benign lesions. If there is recurrence accompanied by a histologic pattern change toward a more unorganized fibrous stroma with displacement of the epithelial component, however, then more extensive treatment procedures appear to be indicated.

Adolescent↗
PubMed1978

Hidroacanthoma simplex with in situ porocarcinoma. A case suggesting malignant transformation.

A case of hidroacanthoma simplex, suggesting malignant transformation into porocarcinoma in situ is reported. It represents further evidence that epidermotropic eccrine carcinoma may originate from the acrosyringium. This lesion demonstrates that the upper portion of the dermal eccrine duct may participate in the oncogenesis of hidroacanthoma simplex. It may also provide the missing link in the chain of evolution of benign eccrine poroacanthoma into porocarcinoma.

Aged↗
PubMed1979

Optical detection of cell-surface changes associated with malignant transformations in vitro.

A need exists for new experimental approaches for the direct detection of cell-surface changes associated with malignant transformations. The usual methods of fractionating the cell to obtain plasma-membrane segments are disruptive and are influenced by uncertainties that frustrate most attempts to distinguish between the cell memebrane in the normal and malignant states. Here we describe a non-destructive microprobe technique using a light beam to monitor cell-surface changes in situ. Many investigations of tumor-cell behavior in culture are based on substrate-adherent populations of cells. By choosing the substrate to be optically dense and transparent, and by striking the substrate/cell interface by a light beam from the substrate side at an angle of incidence greater than the critical angle of total-internal reflection, an evanescent electromagnetic wave interacts with the peripheral zone of the substrate-adherent cells. Both the intensity and ellipse of polarization of the reflected wave can be monitored as the malignant transformation takes place, either chemically or virally. This technique should also provide new information concerning the molecular organization of the cell periphery from measurements on living cells.

Cell Membrane↗
PubMed1979

Malignant transformation of a Warthin tumor: case report, review of the literature, and discussion of pathology.

Papillary cystadenoma lymphomatosum (Warthin's tumor) is generally considered to be a benign tumor. However, a few well-documented cases of malignant transformation have been reported. In each case, the patient had received radiotherapy to the neck region where the tumor later developed. This paper reports a case of malignant transformation of a papillary cystadenoma lymphomatosum (PCL) in a patient who had not received radiotherapy. Light and electron microscopy documented this transformation and clearly identified the malignant portion of the tumor as having its origin in a benign PCL. The literature is reviewed and a discussion of pathology presented.

Adenolymphoma↗
PubMed1979

Role of photosensitization and oxygen in chromosome stability and "spontaneous" malignant transformation in culture.

Visible light and oxygen enhanced both chromosome instability and malignant transformation of mouse cells in culture. Nine cell lines were initiated from 8 pools of 10- to 13-day C3H embryos. Each cell line was divided into sublines, which were either maintained shielded from light or were exposed for 3 or 24 hours to fluorescent light (approximately 150 foot-candles) two or three times weekly. Cultures of the sublines were also maintained with either a gaseous phase of 0-1% oxygen or atmospheric (18%) oxygen. Each line was monitored for cytologic manifestations of malignant neoplastic transformation, and 8 lines were monitored for chromosome alterations. Seven lines were assayed for tumorigenicity by intraocular implantation into syngeneic hosts. Repeated light exposure and/or high oxygen increased the frequency of minute chromosomes, which result from chromatid breaks, and also increased the rate of shift from diploid to heteroploid state. Four cell lines showed no cytologic changes indicative of neoplastic change during the test period. Two of these were assayed in vivo and failed to grow as tumors. In the remaining 6 lines, cytologically neoplastic colonies appeared earlier or more abundantly in the light-exposed cultures and/or those gassed with high oxygen. In 3 of these lines, tumors developed only from the light-exposed cultures; in the other 2, tumor latency periods were significantly shorter in the cultures exposed to light or gassed with atmospheric oxygen.

Animals↗
PubMed1977

[In vitro malignant transformation of fetal hamster brain cells by methylnitrosourea].

Using primary cultures originating from 14 day old fetal Hamster brain, we have obtained a cell line with glial morphology. These cell remain non transplantable during the first year of in vitro culture, but undergo spontaneous transformation during the second year. Following prolonged contact of the glial-like cells with 25 to 50 microgram/ml of methylnitrosourea (MNU), a malignant transformation is observed 5 months after the treatment. The lowest concentrations of (MNU) do not cause malignant transformation, but seem to inhibit (or postpone) the spontaneous transformation. After MNU treatment, cells retain their glial nature.

Animals↗
PubMed1979

Comparison of mutagenesis and malignant transformation by dihydrodiols from benz[a]anthracene and 7,12-dimethylbenz[a]anthracene.

Five dihydrodiols derived from benz[a]anthracene (BA) and 4 dihydrodiols derived from 7,12-dimethylbenz[a]anthracene (DMBA) have been tested, together with the parent hydrocarbons, for their abilities to induce mutations to 8-azaguanine resistance in V79 (Chinese hamster cells and malignant transformation in M2 mouse fibroblasts. The syn- and anti-isomers of benz[a]anthracene 8,9-diol 10,11-oxide were also tested for biological activity in these two systems. The non-K-region 1,2- and 3,4-dihydrodiols of BA induced mutations but the non-K-region 8,9-dihydrodiol and the K-region 5,6-dihydrodiol were inactive as mutagens; none of these BA diols transformed M2 mouse fibroblasts. The 3,4- and the 8,9-dihydrodiols derived from 7,12-dimethylbenz[a]anthracene induced mutations in V79 cells and malignant transformation in M2 mouse fibroblasts and both were more active than the hydrocarbon itself. The K-region 5,6-dihydrodiol and the non-K-region 10,11-dihydrodiol of DMBA were inactive in both test systems. The results are not inconsistent with other data suggesting that the metabolic activation of both BA and DMBA occurs through conversion of the respective 3,4-dihydrodiols into the related vicinal diol-epoxides, although other dihydrodiols may also be involved in vivo. Both the BA diol-epoxides tested were mutagenic, but although the anti-isomer transformed M2 fibroblasts, the syn-isomer was inactive.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1976

Malignant transformation of hamster brain cells in vitro by human papovavirus Bk.

Human papovavirus BK caused the malignant transformation in vitro of brain cells prepared from newborn hamsters. The transformed cells produced BK virus T antigen and grew as tumors after sc inoculation ito hamsters that developed antibodies to BK virus T antigen. The histopathology of the tumors revealed an undifferentiated glioma.

Animals↗
PubMed1979

A new parameter for discriminating malignantly transformed cell lines from nontransformed counterparts: culture in liquid medium containing neutral protease.

Growth properties of malignantly transformed cell lines and their nontransformed counterparts were studied in the presence of a bacterial neutral protease (Dispase I). Among 10 transformed cell lines, 7 lines could proliferate in the presence of the protease in a floating state. Nontransformed cell lines and non-established cell strains failed to grow in this culture condition. The ability to grow in the presence of the protease was well correlated with their ability for anchorage-independent growth and tumorigenicity, and this provides a convenient primary test for evaluating cellular tumorigenicity.

Bacillus↗
PubMed1979

Loss of epidermal growth factor requirement and malignant transformation.

Serum provides growth factors that regulate and limit the growth of normal cells in tissue culture. Animal cells that are malignantly transformed usually exhibit diminished serum requirements for growth in culture. We have used a defined, serum-free medium to determine which of these growth factors becomes dispensable for the growth of transformed Syrian and Chinese hamster fibroblast cells. The medium's four growth factors-epidermal growth factor (EGF), insulin, fibroblast growth factor, and transferrin-were added or omitted as desired. A decreased requirement for EGF was most closely related to tumorigenicity of chemically (ethyl methanesulfonate) transformed cells in nude mice. All lines examined retained their requirement for transferrin, which is needed throughout the growth cycle, in contrast to the other factors, which are needed primarily in G(1) phase. Lines that had lost their EGF requirement but had retained their insulin requirement were arrested in G(1) by insulin deficiency, indicating that their growth control system remained. Mutagenesis with ethyl methanesulfonate can also create requirements of the transformed cells for unknown factors in serum. We conclude that an initial step that reduces the serum requirement in culture, and in tumorigenesis, is relaxation of the growth-regulatory function of EGF.

Blood↗
PubMed1975

Malignant transformation of hamster cells following infection with bovine herpesvirus (infectious bovine rhinotracheitis virus.

Hamster embryo cells, following infection with IBR virus, showed malignant transformation. Hamsters of all ages, inbred or random bred, inoculated with two of the transformed cell lines developed solid tumors. Preliminary characterization of the tumors induced by one of the cell lines has indicated undifferentiated sarcomas. Viral specific antigen was detected in about 5% of the transformed cells and 10% of primary tumor cells in culture. Viral specific antibody was detected in the serum of tumor-bearing hamsters by the indirect immunofluorescent method, but no neutralizing antibodies were found. Infectious virus has not been recovered from either the transformed or tumor cells by cocultivation with bovine embryonic kidney cells.

Animals↗