Mechanism Of Apoptotic Resistance Research Articles

The Apoptotic Resistance of BRCA1-Deficient Ovarian Cancer Cells is Mediated by cAMP.

Breast cancer type 1 susceptibility protein (BRCA1) is essential for homologous recombination repair of DNA double-strand breaks. Loss of BRCA1 is lethal to embryos due to extreme genomic instability and the activation of p53-dependent apoptosis. However, the apoptosis is resisted in BRCA1-deficient cancer cells even though their p53 is proficient. In this study, by analysis of transcriptome data of ovarian cancer patients bearing BRCA1 defects in TCGA database, we found that cAMP signaling pathway was significantly activated. Experimentally, we found that BRCA1 deficiency caused an increased expression of ADRB1, a transmembrane receptor that can promote the generation of cAMP. The elevated cAMP not only inhibited DNA damage-induced apoptosis through abrogating p53 accumulation, but also suppressed the proliferation of cytotoxic T lymphocytes by enhancing the expression of immunosuppressive factors DKK1. Inhibition of ADRB1 effectively killed cancer cells by abolishing the apoptotic resistance. These findings uncover a novel mechanism of apoptotic resistance in BRCA1-deficient ovarian cancer cells and point to a potentially new strategy for treating BRCA1-mutated tumors.

Abstract 730: The role of ZEB1/ZEB2 and βIII-tubulin in mediating docetaxel-resistant prostate cancer

Abstract Docetaxel therapy is the gold standard treatment for advanced castrate-resistant prostate cancer (CRPC). However, patients either do not respond or develop resistance over time. Transcriptomic and proteomic analysis of docetaxel-resistant prostate cancer sub-lines developed by our group revealed multiple mechanisms of resistance in line with advanced disease, including over-expression of anti-apoptotic proteins and alterations of NF-KB activation. The sub-lines also demonstrated a coordinated loss and gain of epithelial and mesenchymal markers respectively; a process characteristic of Epithelial-Mesenchymal Transition (EMT). Studies have highlighted a role of EMT in prostate cancer progression, metastasis and docetaxel resistance. However, the role of EMT drivers in mediating resistance is not defined. We hypothesise EMT to be a central mechanism of apoptotic resistance in advanced docetaxel-resistant prostate cancer, representing a target for therapeutic manipulation. EMT was characterised in the PC-3 D12 and DU145 R docetaxel-resistant sub-lines through an increased invasive capacity, MMP-1 secretion and protein expression of E-cadherin transcriptional repressors ZEB1 and ZEB2, in comparison to parental cell lines. This was associated with an increased expression of βIII-tubulin; a tubulin isotype linked to taxane resistance and tumour aggressiveness. Upon treatment with the apoptotic trigger docetaxel (20nM), the PC-3 D12 and DU145 R sub-lines demonstrated significant resistance compared to parental controls. Simultaneous siRNA knockdown of ZEB1 and ZEB2 resulted in both a partial reversal in apoptotic resistance and a decrease in cell viability; this was also associated with a down-regulation of βIII-tubulin and a re-expression of E-cadherin. Our results provide evidence of the process of EMT in in vitro models of docetaxel-resistant prostate cancer, which is associated with differential susceptibility to docetaxel and is partially reversed through siRNA knockdown of the EMT drivers, ZEB1 and ZEB2. In addition, we have identified a link between EMT and βIII-tubulin in our models of docetaxel resistance. Current experiments are investigating the tissue expression of ZEB1 and βIII-tubulin in prostate cancer metastases following docetaxel therapy, which will determine the clinical relevance of EMT and βIII-tubulin as mediators of docetaxel resistance in CRPC. Citation Format: Karen Hanrahan, Maria Prencipe, Jane Bugler, Lisa Murphy, Amanda O'Neill, R. William Watson. The role of ZEB1/ZEB2 and βIII-tubulin in mediating docetaxel-resistant prostate cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 730. doi:10.1158/1538-7445.AM2015-730

Abstract A60: Late stage intestinal polyps in ApcMin/+ mice are resistant to treatment with retinoids and TRAIL due to up-regulation of pro-survival proteins.

Abstract The purpose of this study is to determine the mechanism of apoptotic resistance observed in advanced polyps in a mouse model of Familial Adenomatous Polyposis (FAP). FAP is an autosomal dominantly inherited disorder caused by mutations in the tumor suppressor Apc (adenomatous polyposis coli) gene, which results in the formation of hundreds to thousands of polyps, predominantly in the colon and rectum. Left untreated, these polyps will form colorectal adenocarcinomas. Although surgical removal of the colon eliminates the colon cancer risk, these individuals are also at increased risk for other primary cancers, including tumors of the small intestine and stomach. Systemic chemopreventive interventions to specifically remove the pre-cancerous cells in these individuals could greatly improve their outcomes and quality of life. Recently, we have developed a new method based on the ability of combined retinoid and TRAIL (tumor necrosis factor related apoptosis inducing ligand) treatment to induce apoptosis and regression of intestinal polyps in ApcMin/+ mice, a mouse model of FAP. Treatment of these mice with retinoid causes an increase in TRAIL death receptors DR4 and DR5 as well as a concomitant decrease in the decoy receptors. APC deficiency leads to a decreased level of the anti-apoptotic protein FLIP (flice-like inhibitory protein). Thus, the combination of TRAIL and retinoid specifically targets APC deficient cells for apoptosis. We have further determined that early stage intestinal polyps in the ApcMin/+ mouse respond readily to this treatment combination, while late stage polyps are resistant to this treatment. Following up on these findings, we have tested the hypothesis that late stage adenomas of the intestine are resistant to TRAIL and retinoid treatment due to increased inflammatory signaling, resulting in increased anti-apoptotic signaling. We used ApcMin/+ mice at either two months of age or five-six months of age. Adenomas from young mice and older mice were subjected to immunoblot and immunohistochemistry comparing the levels of anti-apoptotic proteins as well as markers of inflammation. Results: Polyps from older mice expressed markedly increased levels of the anti-apoptotic proteins FLIP (flice-like inhibitory protein), XIAP (x-linked inhibitor of apoptosis) and Bcl-2. These polyps also exhibited increased staining for the pro-inflammatory protein cox-2 (cyclooxygenase-2) and the transcription factor NFκB (nuclear factor kappa B). Conclusion: The increased inflammation known to occur in older ApcMin/+ mice leads to an increase in pro-survival proteins that inhibits induction of apoptosis. This suggests that pre-treatment with an anti-inflammatory agent such as sulindac might sensitize adenomas in older mice to retinoid and TRAIL treatment for the induction of apoptosis. Citation Format: Jennifer S. Davis, Shaoyi Huang, Xiaoyang Ren, Zhengming Xu, Ernest Hawk, Xiangwei Wu. Late-stage intestinal polyps in ApcMin/+ mice are resistant to treatment with retinoids and TRAIL due to upregulation of prosurvival proteins. [abstract]. In: Proceedings of the Eleventh Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2012 Oct 16-19; Anaheim, CA. Philadelphia (PA): AACR; Cancer Prev Res 2012;5(11 Suppl):Abstract nr A60.

Down-regulation of CYLD as a trigger for NF-κB activation and a mechanism of apoptotic resistance in hepatocellular carcinoma cells

The cylindromatosis gene (CYLD) was identified as a tumor suppressor gene, which is mutated in familial cylindromatosis (Brooke-Spiegler syndrome), an autosomal-dominant predisposition to multiple tumors of the skin appendages. CYLD is a deubiquitinating enzyme acting as a negative regulator of the nuclear factor κB (NF-κB) signaling pathway by removing lysine-63-linked polyubiquitin chains from NF-κB activating proteins. In order to investigate the role of CYLD in apoptotic signaling in human hepatocellular carcinoma (HCC) cells, we first studied the expression levels of CYLD in HCC tissues. CYLD expression was lower in HCC both at protein and mRNA levels compared to the surrounding non-malignant tissue. In order to further study the role of CYLD in the apoptotic sensitivity of HCC cells, CYLD was specifically down-regulated in HCC cell lines via RNA interference. The specific down-regulation of CYLD resulted in increased resistance towards treatment with doxorubicin, 5-fluorouracil and cisplatin. In addition, the down-regulation of CYLD in HCC cells decreased the sensitivity towards tumor necrosis factor-α-induced apoptosis. The CYLD knockdown also led to the degradation of the NF-κB inhibitor, IκB-α, resulting in enhanced NF-κB activity in HCC cells. Finally, we found that CYLD expression was triggered by the multikinase inhibitor, sorafenib, by the inhibition of Raf-1, as well as by the blockage of the pro-survival kinases, MEK (U0126) and the epidermal growth factor receptor (AG1478). In summary, we show that CYLD is down-regulated in human HCC and is involved in the apoptotic resistance of HCC cells. Our data identify the reconstitution of CYLD expression as an attractive approach for overcoming resistance to treatment in HCC.

Tissue Microarray Analysis of Fas and FasL Expressions in Human Non-small Cell Lung Carcinomas; with Reference to the p53 and bcl-2 Overexpressions

Lack of surface Fas expression is a main route for apoptotic resistance which is considered an important mechanism of tumorigenesis and tumor progression. Fas and FasL expressions in 110 non-small cell lung carcinomas (NSCLCs) were investigated to evaluate their roles in pulmonary carcinogenesis and to examine the clinicopathologic significance of Fas expression with its relationship with p53 and bcl-2 overexpressions. Immunohistochemical analysis using tissue microarray demonstrated that a large proportion of NSCLC patients (60%) showed lack of membranous Fas expression. The Fas-negative cases revealed the significantly lower survival rate than Fas-positive ones. Also, the loss of Fas receptor expression was found more frequently in advanced stage and higher nodal status. FasL protein was increased in most NSCLCs (89%) compared to normal lungs. p53 and bcl-2 overexpressions showed no association with Fas expression. Conclusively, reduced membranous Fas expression as a mechanism of apoptotic resistance is considered to play an important part of the pulmonary carcinogenesis, which may predict poor survival and have a bad prognostic influence. Increased FasL expression is thought to be a basis for the immune evasion in NSCLCs. The rare bcl-2 overexpression suggests that this anti-apoptotic protein is unlikely to play a role in the apoptotic resistance of NSCLCs.

Apoptotic resistance to ionizing radiation in pediatric B-precursor acute lymphoblastic leukemia frequently involves increased NF-κB survival pathway signaling

AbstractTo investigate possible causes of the variable response to treatment in pediatric B-precursor acute lymphoblastic leukemia (ALL) and to establish potential novel therapeutic targets, we used ionizing radiation (IR) exposure as a model of DNA damage formation to identify tumors with resistance to p53-dependent apoptosis. Twenty-one of 40 ALL tumors responded normally to IR, exhibiting accumulation of p53 and p21 proteins and cleavage of caspases 3, 7, and 9 and of PARP1. Nineteen tumors exhibited apoptotic resistance and lacked PARP1 and caspase cleavage; although 15 of these tumors had normal accumulation of p53 and p21 proteins, examples exhibited abnormal expression of TRAF5, TRAF6, and cIAP1 after IR, suggesting increased NF-κB prosurvival signaling as the mechanism of apoptotic resistance. The presence of a hyperactivePARP1mutation in one tumor was consistent with such increased NF-κB activity. PARP1 inhibition restored p53-dependent apoptosis after IR in these leukemias by reducing NF-κB DNA binding and transcriptional activity. In the remaining 4 ALL tumors, apoptotic resistance was associated with aTP53mutation or with defective activation of p53. We conclude that increased NF-κB prosurvival signaling is a frequent mechanism by which B-precursor ALL tumors develop apoptotic resistance to IR and that PARP1 inhibition may improve the DNA damage response of these leukemias.

Mechanism of apoptotic resistance of human osteosarcoma cell line, HS-Os-1, against irradiation

In our previous study, we examined reactive oxygen species (ROS) formation in T lymphocytes following 5 Gy of irradiation. Using a CCD camera system, we monitored fluorescence in T lymphocytes loaded with the succinimidyl ester of Dichlorodihydrofluorescein diacetate (H2DCFDA), which is non-fluorescent until oxidized by ROS. We found that ROS formation occurred immediately after irradiation, continued for several hours, and resulted in oxidative DNA damage. Therefore, the origin of the hyper-radiosensitivity of T lymphocytes seemed to be the high production of ROS in the mitochondrial DNA following irradiation. In this study, we examined radiation-induced ROS formation, oxidative DNA damage, early apoptotic changes, and mitochondrial membrane dysfunction in the human osteosarcoma cell line HS-Os-1, which was established from an osteoblastic tumor that arose in the left humerus of an 11-year-old girl and was already morphologically characterized in vitro and in vivo. We found that ROS formation and oxidative DNA damage were actually scarcely seen after irradiation of up to 30 Gy in these cells; that mitochondrial membrane potential was preserved; and that apoptotic changes were not demonstrated despite the relatively high-dose irradiation of 30 Gy. Therefore, the origin of the close similarity of radiosensitivity between adult articular chondrocytes and the human osteosarcoma cell line HS-Os-1, is considered to involve the low degree of ROS formation following irradiation; the similarity possibly results from the strong scavenging ability of these two kinds of cells for free radicals including hydroxyl radicals.