Genes mediating programmed cell death: an immunohistochemical study of bcl-2, c-myc and p53 expression in colorectal neoplasia

Oncogenic lncRNA MALAT-1 recruits E2F1 to upregulate RAD51 expression and thus promotes cell autophagy and tumor growth in non-small cell lung cancer

INTRODUCTION

LncRNA MALAT-1 expression is involved in regulating activities of non-small-cell lung cancer (NSCLC) cells. This study aimed to investigate the effects of lncRNA MALAT-1 on chemosensitivity of NSCLC cells by regulating autophagy.

METHODS

We first validated the expression of lncRNA MALAT-1 in NSCLC cell lines. NSCLC cell lines with high lncRNA MALAT-1 expression were exposed to doxorubicin (DOX) to assess chemosensitivity. Further LncMAP database retrieval and ChIP, RIP and luciferase activity assays were conducted to explore interplay between lncRNA MALAT-1, RAD51, and E2F1. Immunofluorescence staining was performed to evaluate formation of autophagosomes in NSCLC cells. Ectopic expression and knockdown methods were used for in vitro mechanism experiments and in vivo substantiation.

RESULTS

LncRNA MALAT-1 was overexpressed in NSCLC cells, and could promote NSCLC cell autophagy and inhibit its chemosensitivity. In vitro cell mechanism verification experiments showed that lncRNA MALAT-1 could recruit transcription factor E2F1 to bind to the promoter of RAD51, so as to promote the transcriptional expression of RAD51. In addition, cell function experiments in vitro showed that ectopically expressed lncRNA MALAT-1 promoted NSCLC cell autophagy and inhibited its chemosensitivity, while RAD51 knockdown negated its effect. Finally, in vivo animal experiments confirmed that lncRNA MALAT-1 silencing could impede the tumor growth.

CONCLUSIONS

Taken together, this study revealed that silencing lncRNA MALAT-1 enhanced chemosensitivity of NSCLC cells by promoting autophagy, highlighting a feasible approach to prevent chemoresistance in NSCLC treatment.

Predicting transition from oral pre-malignancy to malignancy via Bcl-2 immuno-expression: Evidence and lacunae

Bcl-2 (B cell Lymphoma -2) family comprises of both anti-apoptotic and pro-apoptotic proteins whose altered expression or change in ratio inhibits apoptosis, and promotes tumor progression. The aim of this study is to assess the usefulness of Bcl-2 in distinguishing dysplastic or malignant epithelium from non-dysplastic or normal epithelium to aid in prediction of malignant transformation potential.

Material and method

Study group comprised of 30 cases of clinically diagnosed leukoplakia (OPMD), 15 cases of Oral Squamous Cell Carcinoma (OSCC) and 5 normal tissue samples. The labeling index of Bcl-2 was analyzed in immunohistochemically stained sections. Different statistical tools were used to analyze the data and to compare Bcl-2 expression qualitatively and quantitatively among all the groups.

Results

An increasing trend of Bcl-2 immunoexpression was observed from normal epithelium to non-dysplastic and from non-dysplastic to dysplastic lesions. In OSCC, the peripheral cells in the differentiating epithelial islands (within the connective tissue) showed Bcl-2 immuno-reactivity, which gradually decreased towards the center. In contrast, intense and diffuse Bcl-2 immuno-reactivity was seen in poorly differentiated carcinoma. But the overall Bcl-2 positivity was less in OSCC as compared to dysplastic lesions.

Conclusion

Increased expression of Bcl-2 oncoprotein in sequentially progressing epithelial dysplasia and down-regulation in differentiating carcinoma (well and moderately differentiating OSCC) unveils the clinical relevance of Bcl-2 in early stages of OSCC tumorigenesis. The heterogenous expression of Bcl-2 in carcinoma with different grades of differentiation renders them unable to be used as an independent tool for predicting transition from oral pre-malignancy to malignancy.

Bcl-2 and c-Myc expression in oral dysplasia and oral squamous cell carcinoma: An immunohistochemical study to assess tumor progression

Introduction

Oral cancer is a multistep process involving foul play of proto-oncogenes that induce cell proliferation, inactivation of tumor suppressor gene and cessation of programmed cell death. Among various proto-oncogenes, the nature and behavior of Bcl-2 and c-Myc in oral precancerous/cancerous lesions were obscured which require further assessment for better understanding of etiology, treatment and prognosis.

Aim

The aim of the study is to assess the expression of Bcl-2 and c-Myc in oral epithelial dysplasia and oral squamous cell carcinoma (OSCC).

Materials and Methods

This retrospective study of 70 (oral dysplasia [30], OSCC [30] and normal gingiva [10]) is immunohistochemically assessed for Bcl-2 and c-Myc for distribution, intensity, percentage of positive cells, localization and immunoreactive scores using ImageJ software.

Results

Bcl-2 showed 60% and 37% positivity within dysplasia and OSCC, respectively (P = 0.03); c-Myc showed 87% and 90% positivity within dysplasia and OSCC, respectively. In OSCC, c-Myc showed moderate intensity (P = 0.04). Average percentage of positive cells expressing c-Myc and Bcl-2 increased proportionally within grades of dysplasia (P = 0.000 and P = 0.008, respectively), whereas in OSCC, only c-Myc showed significant expression (P = 0.021). Localization of c-Myc was seen in the nucleus among OSCC (P = 0.01). c-Myc and Bcl-2 showed moderate immunoreactivity in dysplasia (P = 0.005 and P = 0.013, respectively), whereas in OSCC, moderate immunoreactivity of c-Myc (P = 0.05) was observed.

Conclusion

Variable expression of c-Myc and Bcl-2 reveals that these proteins act in synergism in early phases of carcinogenesis, whereas in later stages, due to the diminished activity of Bcl-2, c-Myc interacts incoordination with other oncogenes contributing to tumor progression.

Apoptosis and colorectal cancer: implications for therapy

Colorectal cancer (CRC) is characterized by the partial suppression of apoptosis, which in turn gives tumours a selective advantage for survival and can cause current chemotherapy approaches to be ineffective. Recent progress in understanding the mechanisms of apoptosis in colorectal carcinogenesis has provided potential new targets for therapy. Here, we review recent studies of the regulation of apoptosis and its role in CRC initiation and progression, and we discuss the relationship between chemoresistance and the suppression of apoptosis. Recent progress in targeting apoptotic pathways and their regulators provide strategies for the exploration of novel therapies for CRC.

Cell turnover of serrated adenomas

Serrated adenomas of the colon are characterized by epithelial neoplasia combining the architectural features of hyperplastic polyps and the cytological features of adenomas. Cell turnover, which is related to the malignant potential of these polyps, has not been thoroughly investigated. The aim of this study was to investigate epithelial cell proliferation, apoptosis, and oncoprotein expression in serrated adenomas. Twenty-five hyperplastic polyps, 25 serrated adenomas, and 25 tubulovillous adenomas resected from the colons of 75 patients were studied by immunohistochemical staining using monoclonal antibodies against MIB-1, Bcl-2, Bax, p53, and the TUNEL method for the detection of apoptosis. In serrated adenomas, the proliferation rate was significantly lower than in tubulovillous adenomas in both the lower and the upper parts of the crypts, and higher than that of hyperplastic polyps. Apoptosis was also significantly lower in serrated than in tubulovillous adenomas, but higher than in hyperplastic polyps. p53 oncoprotein expression was significantly greater in both serrated and tubulovillous adenomas than in hyperplastic polyps. bcl-2 protein expression was higher only in tubulovillous adenomas. Bax index was significantly different between tubullovillous and serrated adenomas, but the lowest values were observed in hyperplastic polyps. Serrated adenomas are highly proliferative polyps. They should be considered a biologically different entity from hyperplastic polyps. The intermediate features between serrated adenomas, hyperplastic polyps, and tubulovillous adenomas using the antibodies analysed in this study could have implications for the rate or the mechanism of development of malignancy in this type of polyp.

Immunolocalizaiton of c-Myc and bcl-2 proto-oncogene products in gingival hyperplasia induced by nifedipine and phenytoin

BACKGROUND

Hyperplastic gingival tissues show the histopathological characteristics of thick parakeratinized squamous epithelia with acanthosis and rete pegs elongated into the lamina propria. However, the pathogenic factors that contribute to the epithelial morphogenesis of this disease are obscure and remain to be studied.

METHODS

We immunohistochemically examined the expression of both c-Myc and bcl-2 oncoprotein, which can exert influence on the epithelial morphogenesis and homeostasis, in 12 hyperplastic gingival tissues induced by nifedipine and phenytoin as well as 5 control tissues using avidin-biotin-peroxidase complex methods.

RESULTS

Four specimens out of 5 nifedipine-induced and 5 out of 7 phenytoin-induced hyperplastic gingival tissues revealed the expression of c-Myc oncoprotein, whereas no significant immunostaining of c-Myc oncoprotein was found in 5 control tissues. The c-Myc oncoprotein-positive cells were observed to be localized in the basal and suprabasal cell layers of the hyperplastic gingival epithelia. Although all of the 12 hyperplastic gingival epithelia showed the distribution of bcl-2 oncoprotein in the basal and suprabasal layer cells, in 5 control epithelia the bcl-2 oncoprotein expression was slight and confined to the basal layer cells.

CONCLUSIONS

The results of our present study indicate that the synergistic overexpression of c-Myc and bcl-2 oncoprotein may be related to the pathogenesis of gingival hyperplasia induced by nifedipine and phenytoin, especially to the morphogenesis of hyperplastic epithelia.

Deregulation of apoptosis in colorectal carcinoma: theoretical and therapeutic implications

Apoptosis, or programmed cell death, maintains the structure of the colonic crypts by providing a balance to the rate of cell proliferation. Colorectal carcinoma arises partly from a disruption in this balance in the favour of uncontrolled growth. Until recently, most research into colon cancer has focused on the molecular regulators of cell-cycle progression and proliferation, but it is now evident that apoptosis is also defective. A failure of cells to die in response to premalignant damage may allow the progression of the disease and maintain the resistance of cancer cells to cytotoxic therapy. This review outlines the importance of apoptosis in the normal colon and presents recent studies that demonstrate that induction of apoptosis is defective in colonic tumours. When the molecular regulation of apoptosis is better understood, this knowledge may lead to the earlier detection of patients at greater risk of developing colorectal carcinoma, and also to the development of more effective therapies.

Apoptosis is associated with atypical or malignant change in meningiomas. An in situ labelling and immunohistochemical study

AIMS

Although necrosis is an important phenomenon with implications for grading and prognostication in meningiomas, the alternate form of cell death, apoptosis, has not been extensively studied. In this series, we aimed to determine whether apoptosis in meningiomas correlated with histological types and grading. We also looked for a relationship between expression of apoptosis-related genes bcl-2, p53, c-myc and apoptosis meningiomas.

METHODS AND RESULTS

Fifty-one meningiomas of diverse histological subtypes and grades were investigated with in situ end-labelling of DNA fragments as well as immunohistochemical analysis of three apoptosis-related genes: p53, bcl-2 and c-myc. Our results showed that the apoptosis index was significantly higher in high-grade meningiomas (0.12%, n = 12) in than the benign meningiomas (0.023%, n = 39) P = 0.001) but there was no difference among the different histological subtypes of the benign meningiomas (P = 0.125). There is no obvious relationship between p53, bcl-2 and c-myc staining and apoptosis index in this group of meningiomas.

CONCLUSION

We conclude that apoptosis is an important phenomenon in meningiomas and that it is associated with atypical or malignant changes in meningiomas. Apoptosis in meningiomas has no clearcut relationship with expression of p53, bcl-2 and c-myc.

A histopathological assessment of the response of rectal adenocarcinoma to combination chemo-radiotherapy: relationship to apoptotic activity, p53 and bcl-2 expression

AIMS

To investigate the use of pre-operative chemo-irradiation in downstaging advanced rectal cancer prior to surgical resection.

METHODS

We examined the pathological effects of chemo-irradiation on 24 rectal tumours and correlated the efficacy of treatment with the level of apoptosis, mitosis, P53 and bcl-2 protein expression on pre-treatment biopsies.

RESULTS

All tumours were resectable following chemo-irradiation. Six cancers showed complete regression with no viable tumour in the resection specimen. A significant correlation was found between spontaneous tumour apoptosis and tumour regression.

CONCLUSIONS

Our results suggest that in rectal cancer the apoptotic rate in untreated tumour tissue may predict sensitivity to radiation and cytotoxic agents. No relationship was found between regression and mitotic rate, p53 or bcl-2 expression.

Down-regulation of Fas gene expression in colon cancer is not a result of allelic loss or gene rearrangement

Expression of Fas, an apoptosis-inducing receptor, in colonic epithelium is progressively reduced during malignant transformation. We have examined the human Fas gene for loss of heterozygosity (LOH) and gross rearrangements in colon tumours and matched normal mucosa. Polymerase chain reaction (PCR) primers were designed to span a DraI restriction fragment length polymorphic site in the gene. Heterozygosity was detected in normal DNA samples by PCR amplification of the polymorphic site and restriction enzyme digestion. Thirty-eight of 88 patients (43%) with colon carcinomas were informative for the assay, and LOH was detected in 6 of the 38 (16%) corresponding tumours. Tumours from three patients with LOH did not express detectable Fas mRNA, and Fas expression was reduced or absent in 7 of 11 tumours from informative patients without LOH. Southern blotting of tumour DNA samples was used to detect rearrangement of the Fas gene, but no altered hybridization patterns were observed in 64 tumours analysed. These findings indicate that disruption of the Fas gene is not primarily responsible for the loss of Fas protein expression reported in colon cancer. We have also shown that loss of Fas gene transcription is common in these tumours, which may be due to epigenetic gene silencing.