Differential effects of coverslip-induced hypoxia and cobalt chloride mimetic hypoxia on cellular stress, metabolism, and nuclear structure.

Hypoxia has profound effects on cell physiology, both in normal or pathological settings like cancer. In this study, we asked whether a variant of coverslip-induced hypoxia that recapitulates the conditions found in the tumor microenvironment would elicit similar cellular responses compared to the well established model of cobalt chloride-induced hypoxia. Comparable levels of nuclear HIF-1α were observed after 24 h of coverslip-induced hypoxia or cobalt chloride treatment in CAL-27 oral squamous carcinoma cells. However, cellular stress levels assessed by reactive oxygen species production and lipid droplet accumulation were markedly increased in coverslip-induced hypoxia compared to cobalt chloride treatment. Conversely, mitochondrial ATP production sharply decreased after coverslip-induced hypoxia but was preserved in the presence of cobalt chloride. Coverslip-induced hypoxia also had profound effects in nuclear organization, assessed by changes in nuclear dry mass distribution, whereas these effects were much less marked after cobalt chloride treatment. Taken together, our results show that coverslip-induced hypoxia effects on cell physiology and structure are more pronounced than mimetic hypoxia induced by cobalt chloride treatment. Considering also the simplicity of coverslip-induced hypoxia, our results therefore underscore the usefulness of this method to recapitulate in vitro the effects of hypoxic microenvironments encountered by cells in vivo.

Contributions of viral oncogenes of HPV-18 and hypoxia to oxidative stress and genetic damage in human keratinocytes.

Infection with high-risk human papillomaviruses like HPV-16 and HPV-18 is highly associated with the development of cervical and other cancers. Malignant transformation requires viral oncoproteins E5, E6 and E7, which promote cell proliferation and increase DNA damage. Oxidative stress and hypoxia are also key factors in cervical malignant transformation. Increased levels of reactive species of oxygen (ROS) and nitrogen (RNS) are found in the hypoxic tumor microenvironment, promoting genetic instability and invasiveness. In this work, we studied the combined effect of E5, E6 and E7 and hypoxia in increasing oxidative stress and promoting DNA damage and nuclear architecture alterations. HaCaT cells containing HPV-18 viral oncogenes (HaCaT E5/E6/E7-18) showed higher ROS levels in normoxia and higher levels of RNS in hypoxia compared to HaCaT parental cells, as well as higher genetic damage in hypoxia as measured by γH2AX and comet assays. In hypoxia, HaCaT E5/E6/E7-18 increased its nuclear dry mass and both cell types displayed marked heterogeneity in nuclear dry mass distribution and increased nuclear foci. Our results show contributions of both viral oncogenes and hypoxia to oxidative stress, DNA damage and altered nuclear architecture, exemplifying how an altered microenvironment combines with oncogenic transformation to promote tumor progression.

Artificial Intelligence for Image Analysis in Oral Squamous Cell Carcinoma: A Review.

Head and neck tumor differential diagnosis and prognosis have always been a challenge for oral pathologists due to their similarities and complexity. Artificial intelligence novel applications can function as an auxiliary tool for the objective interpretation of histomorphological digital slides. In this review, we present digital histopathological image analysis applications in oral squamous cell carcinoma. A literature search was performed in PubMed MEDLINE with the following keywords: "artificial intelligence" OR "deep learning" OR "machine learning" AND "oral squamous cell carcinoma". Artificial intelligence has proven to be a helpful tool in histopathological image analysis of tumors and other lesions, even though it is necessary to continue researching in this area, mainly for clinical validation.

Mechanical profile of human keratinocytes expressing HPV-18 oncogenes.

During tumorigenesis, the mechanical properties of cancer cells change markedly, with decreased stiffness often accompanying a more invasive phenotype. Less is known about the changes in mechanical parameters at intermediate stages in the process of malignant transformation. We have recently developed a pre-tumoral cell model by stably transducing the immortalized but non-tumorigenic human keratinocyte cell line HaCaT with the E5, E6 and E7 oncogenes from HPV-18, one of the leading causes of cervical cancer and other types of cancer worldwide. We have used atomic force microscopy (AFM) to measure cell stiffness and to obtain mechanical maps of parental HaCaT and HaCaT E5/E6/E7-18 cell lines. We observed a significant decrease in Young's modulus in HaCaT E5/E6/E7-18 cells measured by nanoindentation in the central region, as well as decreased cell rigidity in regions of cell-cell contact measured by Peakforce Quantitative Nanomechanical Mapping (PF-QNM). As a morphological correlate, HaCaT E5/E6/E7-18 cells displayed a significantly rounder cell shape than parental HaCaT cells. Our results therefore show that decreased stiffness with concomitant perturbations in cell shape are early mechanical and morphological changes during the process of malignant transformation.

Hypoxia, acidification and oxidative stress in cells cultured at large distances from an oxygen source.

Hypoxia is a condition frequently encountered by cells in tissues, whether as a normal feature of their microenvironment or subsequent to deregulated growth. Hypoxia can lead to acidification and increased oxidative stress, with profound consequences for cell physiology and tumorigenesis. Therefore, the interplay between hypoxia and oxidative stress is an important aspect for understanding the effects of hypoxic microenvironments on cells. We have used a previously developed variant of the method of coverslip-induced hypoxia to study the process of acidification in a hypoxic microenvironment and to simultaneously visualize intracellular levels of hypoxia and oxidative stress. We observed high accumulation of CO2 in hypoxic conditions, which we show is the main contributor to acidification in our model. Also, increased levels of oxidative stress were observed in moderately hypoxic cells close to the oxygen source, where the mitochondrial membrane potential was preserved. Conversely, cells at large distances from the oxygen source showed higher levels of hypoxia, milder oxidative stress and reduced mitochondrial membrane potential. Our results contribute to characterize the interplay between reduced oxygen levels, acidification and oxidative stress in a simple in vitro setting, which can be used to model cell responses to an altered environment, such as the early tumor microenvironment.

Estudio de los efectos de un microambiente hipóxico en queratinocitos humanos in vitro y su correlato con alteraciones del microambiente en la patología de liquen plano oral

La hipoxia es un factor fundamental en el proceso de génesis tumoral, así como en patologías precursoras de cáncer, como es el Liquen Plano Oral (LPO). Objetivo: Determinar si es posible establecer una correlación entre las alteraciones que sufren queratinocitos normales en un microambiente hipóxico in vitro y alteraciones que aparecen en los queratinocitos en el epitelio de la mucosa oral en el contexto de la patología LPO. Métodos: Se estudiaron los cambios morfológicos mediante microscopía de contraste de fases, y la detección de marcadores asociados a hipoxia de queratinocitos humanos (HaCaT), como modelo celular oral, en un microambiente hipóxico generado por la variante del método "Hipoxia inducida por cubreobjetos". Resultados: Mediante microscopía confocal se observó la presencia de los marcadores de hipoxia GLUT-1 y aductos de pimonidazol (Hipoxyprobe) en los cultivos celulares de HaCaT expuestos a un microambiente hipóxico. Además, se observó la presencia del marcador GLUT-1 mediante inmunohistoquímica en tejido epitelial humano derivado de biopsias de la patología LPO. Conclusiones: Se estableció una correlación entre las alteraciones detectadas en queratinocitos humanos inducidos a un microambiente hipóxico in vitro y las alteraciones detectadas in vivo en tejido epitelial de la mucosa oral.

A hipóxia é um fator fundamental no processo de gênese tumoral, bem como em patologias precursoras do câncer, como o Líquen Plano Oral (LPO). Objetivo: Determinar se é possível estabelecer uma correlação entre as alterações que os queratinócitos normais sofrem em um microambiente hipóxico in vitro e as alterações que aparecem nos queratinócitos no epitélio da mucosa oral no contexto da patologia do LPO. Métodos: As alterações morfológicas foram estudadas por microscopia de contraste de fase e a detecção de marcadores associados à hipóxia de queratinócitos humanos (HaCaT), como modelo de célula oral, em um microambiente hipóxico gerado pela variante do método "Hipóxia induzida por lamínulas". Resultados: Por microscopia confocal, observou-se a presença dos marcadores de hipóxia GLUT-1 e Hipoxyprobe em culturas de células HaCaT expostas a um microambiente hipóxico. Além disso, a presença do marcador GLUT-1 foi observada por imuno-histoquímica em tecido epitelial humano derivado de biópsias de patologia de LPO. Conclusões: Foi estabelecida uma correlação entre as alterações detectadas em queratinócitos humanos induzidas em um microambiente hipóxico in vitro e as alterações detectadas in vivo no tecido epitelial da mucosa oral.

Hypoxia is a fundamental factor in the process of tumor genesis, as well as in precursor pathologies of cancer, such as Oral Lichen Planus (OLP). Objective: To determine if it is possible to establish a correlation between the alterations that normal keratinocytes suffer in a hypoxic microenvironment in vitro and alterations that appear in the keratinocytes in the epithelium of the oral mucosa in the context of OLP pathology. Methods: Morphological changes were studied by phase contrast microscopy, and the detection of markers associated with hypoxia of human keratinocytes (HaCaT), as an oral cell model, in a hypoxic microenvironment generated by the variant of the method "Hypoxia induced by coverslips". Results: Using confocal microscopy, the presence of hypoxia markers GLUT-1 and Hipoxyprobe was observed in HaCaT cell cultures exposed to a hypoxic microenvironment. In addition, the presence of the GLUT-1 marker was observed by immunohistochemistry in human epithelial tissue derived from biopsies of OLP pathology. Conclusions: A correlation was established between the alterations detected in human keratinocytes induced in a hypoxic microenvironment in vitro and the alterations detected in vivo in epithelial tissue of the oral mucosa.

Human papillomavirus type 18 E5 oncoprotein cooperates with E6 and E7 in promoting cell viability and invasion and in modulating the cellular redox state.

BACKGROUND: High-risk human papillomaviruses (HR-HPVs) are the etiological agents of cervical cancer. Among them, types 16 and 18 are the most prevalent worldwide. The HPV genome encodes three oncoproteins (E5, E6, and E7) that possess a high transformation potential in culture cells when transduced simultaneously. In the present study, we analysed how these oncoproteins cooperate to boost key cancer cell features such as uncontrolled cell proliferation, invasion potential, and cellular redox state imbalance. Oxidative stress is known to contribute to the carcinogenic process, as reactive oxygen species (ROS) constitute a potentially harmful by-product of many cellular reactions, and an efficient clearance mechanism is therefore required. Cells infected with HR-HPVs can adapt to oxidative stress conditions by upregulating the formation of endogenous antioxidants such as catalase, glutathione (GSH), and peroxiredoxin (PRX). OBJECTIVES: The primary aim of this work was to study how these oncoproteins cooperate to promote the development of certain cancer cell features such as uncontrolled cell proliferation, invasion potential, and oxidative stress that are known to aid in the carcinogenic process. METHODS: To perform this study, we generated three different HaCaT cell lines using retroviral transduction that stably expressed combinations of HPV-18 oncogenes that included HaCaT E5-18, HaCaT E6/E7-18, and HaCaT E5/E6/E7-18. FINDINGS: Our results revealed a statistically significant increment in cell viability as measured by MTT assay, cell proliferation, and invasion assays in the cell line containing the three viral oncogenes. Additionally, we observed that cells expressing HPV-18 E5/E6/E7 exhibited a decrease in catalase activity and a significant augmentation of GSH and PRX1 levels relative to those of E5, E6/E7, and HaCaT cells. MAIN CONCLUSIONS: This study demonstrates for the first time that HPV-18 E5, E6, and E7 oncoproteins can cooperate to enhance malignant transformation.

The Asian-American variant of human papillomavirus type 16 exhibits higher activation of MAPK and PI3K/AKT signaling pathways, transformation, migration and invasion of primary human keratinocytes.

Asian-American (AA) HPV-16 variants are associated with higher risk of cancer. Abnormal activation of intracellular signaling play a critical role in cancer development and progression. Our aim was to elucidate mechanisms underlying the higher oncogenic potential attributed to AA variant. We evaluated activation of MAPK and PI3K/AKT pathways in primary human keratinocytes (PHKs) transduced with E6/E7 of three HPV-16 variants: E-P, AA, E-350G. Phenotypes examined included migration, anchorage independent growth and invasion. AA PHKs presented the highest levels of active proteins involved in all cascades analyzed: MAPK-ERK, MAPK-p38 and PI3K-AKT. AA PHKs were more efficient in promoting anchorage independent growth, and in stimulating cell migration and invasion. MEK1 inhibition decreased migration. The mesenchymal phenotype marker vimentin was increased in AA PHKs. Our results suggest that MEK1, ERK2, AKT2 hyperactivation influence cellular behavior by means of GSK-3b inactivation and EMT induction prompting AA immortalized PHKs to more efficiently surpass carcinogenesis steps.

Effect of genetic ancestry on leukocyte global DNA methylation in cancer patients.

BACKGROUND: The study of genetic variants alone is not enough to explain a complex disease like cancer. Alterations in DNA methylation patterns have been associated with different types of tumor. In order to detect markers of susceptibility for the development of cutaneous melanoma and breast cancer in the Uruguayan population, we integrated genetic and epigenetic information of patients and controls. METHODS: We performed two case-control studies that included 49 individuals with sporadic cutaneous melanoma and 73 unaffected controls, and 179 women with sporadic breast cancer and 209 women controls. We determined the level of global leukocyte DNA methylation using relative quantification of 5mdC by HPLC, and we compared methylation levels between cases and controls with nonparametric statistical tests. Since the Uruguayan population is admixed and both melanoma and breast cancer have very high incidences in Uruguay compared to other populations, we examined whether individual ancestry influences global leucocyte DNA methylation status. We carried out a correlation analysis between the percentage of African, European and Native American individual ancestries, determined using 59 ancestry informative markers, and global DNA methylation in all participants. RESULTS: We detected global DNA hypomethylation in leukocytes of melanoma and breast cancer patients compared with healthy controls (p < 0.001). Additionally, we found a negative correlation between African ancestry and global DNA methylation in cancer patients (p <0.005). CONCLUSIONS: These results support the potential use of global DNA methylation as a biomarker for cancer risk. In addition, our findings suggest that the ancestral genome structure generated by the admixture process influences DNA methylation patterns, and underscore the importance of considering genetic ancestry as a modifying factor in epigenetic association studies in admixed populations such as Latino ones.

Determinación de la mutación BRAF V600E en melanomas de pacientes uruguayos / Determination of BRAF V600E mutation in uruguayan patientÆs melanomas

Introducción: la identificación de cambios genéticos que están en la base de la génesis del melanoma ha permitido el desarrollo de terapias dirigidas específicamente contra ellos, lo que determinó, por primera vez en la historia del tratamiento sistémico del melanoma, un incremento en la sobrevida de los pacientes con enfermedad avanzada. Los mejores resultados se han obtenido con vemurafenib, terapia dirigida con-tra BRAF y que solo es efectiva cuando existe la mutación V600E, por lo que su frecuencia en una población determina-da mide el impacto que podría tener en términos de salud.Objetivo: evaluar la frecuencia de la mutación V600E en BRAF en melanomas provenientes de pacientes uruguayos.Material y método: se tomaron 28 muestras de melanoma microdisecadas y se les realizó la investigación de la mutación V600E mediante ASO-PCR (allele specific oligonucleotide - polymerase chain reaction).Resultados: se logró amplificar el ácido desoxirribonucleico (ADN) en 27 de las 28 muestras y se detectó la mutación en21 de ellas (FR: 0,78).Discusión: trabajos previos muestran una frecuencia menor de melanomas portadores de la mutación V600E de BRAF (40%-60% en población caucásica y 25% en población asiática) a la observada en nuestro estudio. Nuestros resultados, si bien requieren confirmación mediante la inclusión de unmayor número de pacientes, podrían explicarse, al menos en parte, por diferencias en la técnica utilizada y tal vez por una proporción diferente de pacientes con melanomas asociadoscon exposición solar intermitente.

Introduction: identifying genetic changes that occur in melanoma genesis has enabled the development of therapies that are specifically geared against such changes, what resulted in an increase of patientsÆ survival for thefirst time in the history of systemic treatment of melanoma, in patients with advanced disease. The best resultshave been obtained with vemurafenib, a therapy that targets the BRAF protein and is only effective in the presence of the V600E mutation. Thus, its frequency in a certain population measures its potential impact in health figures.Objective: to evaluate the frequency of the V600E mutation in BRAF in melanomas of Uruguayan patients.Method: 28 samples of microdissected melanoma were studied and V600E mutation was tested through ASO-PCR (allele specific oligonucleotide - polymerase chain reaction).Results: we managed to amplify DNA in 27 out of the 28 samples and the mutation was identified in 21 ofthem (FR: 0.78).Discussion: previous works demonstrated a lower presence of melanomas that are carriers of the V600E mutation of BRAF (40%-60% in the Caucasian population and 25% in the Asian population) than what ourstudy revealed. Our results, in spite of the need to include a larger number of patients, could partially be due todifferences in the technique used and maybe as a consequence of a different proportion of patients with melanomas associated to the intermittent sun exposure.

Introdução: a identificação de alterações genéticas associadas a origem do melanoma permitiram desenvolver terapias orientadas especificamente contra elas, o que possibilitou, pela primeira vez na história do tratamento sistêmico do melanoma, um aumento da sobrevida dos pacientes com doença avançada. Os melhores resultados foram obtidos com vemurafenib, terapia dirigida contra BRAF e que somente é efetiva quando existe a mutação V600E; sua frequência em uma população determinada mede o impacto que poderia ter sobre asaúde dessa população.Objetivo: avaliar a frequência da mutação V600E em BRAF em melanomas provenientes de pacientesuruguaios.Material e método: foram obtidas 28 amostras microdissecadas de melanoma nas quais fez-se uma pesquisa da mutação V600E utilizando ASO-PCR (allele specific oligonucleotide - polymerase chain reaction).Resultados: foi possível amplificar o ácido desoxirribonucleico (ADN) em 27 das 28 amostras; a mutação foi detectada em 21(FR: 0,78).Discussão: trabalhos anteriores mostram uma frequência menor de melanomas portadores da mutaçãoV600E de BRAF (40%-60% na população caucásica e 25% na população asiática) à observada no nosso estudo. Nossos resultados, embora seja necessário realizarum estudo com um maior número de pacientes, poderiam ser explicados, pelo menos parcialmente, pelas diferenças na técnica utilizada e talvez por una proporção diferente de pacientes com melanomas associados com exposição solar intermitente.