Acquisition Of Anoikis Resistance Research Articles

Exploring the prognostic value of BRMS1 + microglia based on single-cell anoikis regulator patterns in the immunologic microenvironment of GBM.

Anoikis is a specialized form of programmed cell death induced by the loss of cell adhesion to the extracellular matrix (ECM). Acquisition of anoikis resistance is a significant marker for cancer cell invasion, metastasis, therapy resistance, and recurrence. Although current research has identified multiple factors that regulate anoikis resistance, the pathological mechanisms of anoikis-mediated tumor microenvironment (TME) in glioblastoma (GBM) remain largely unexplored. Utilizing single-cell RNA sequencing (scRNA-seq) data and employing non-negative matrix factorization (NMF), we identified and characterized TME cell clusters with distinct anoikis-associated gene signatures. Prognostic and therapeutic response analyses were conducted using TCGA and CGGA datasets to assess the clinical significance of different TME cell clusters. The spatial relationship between BRMS1 + microglia and tumor cells was inferred from spatial transcriptome RNA sequencing (stRNA-seq) data. To simulate the tumor immune microenvironment, co-culture experiments were performed with microglia (HMC3) and GBM cells (U118/U251), and microglia were transfected with a BRMS1 overexpression lentivirus. Western blot or ELISA were used to detect BRMS1, M2 macrophage-specific markers, PI3K/AKT signaling proteins, and apoptosis-related proteins. The proliferation and apoptosis capabilities of tumor cells were evaluated using CCK-8, colony formation, and apoptosis assays, while the invasive and migratory abilities of tumor cells were assessed using Transwell assays. NMF-based analysis successfully identified CD8 + T cell and microglia cell clusters with distinct gene signature characteristics. Trajectory analysis, cell communication, and gene regulatory network analyses collectively indicated that anoikis-mediated TME cell clusters can influence tumor cell development through various mechanisms. Notably, BRMS1 + AP-Mic exhibited an M2 macrophage phenotype and had significant cell communication with malignant cells. Moreover, high expression of BRMS1 + AP-Mic in TCGA and CGGA datasets was associated with poorer survival outcomes, indicating its detrimental impact on immunotherapy. Upregulation of BRMS1 in microglia may lead to M2 macrophage polarization, activate the PI3K/AKT signaling pathway through SPP1/CD44-mediated cell interactions, inhibit tumor cell apoptosis, and promote tumor proliferation and invasion. This pioneering study used NMF-based analysis to reveal the important predictive value of anoikis-regulated TME in GBM for prognosis and immunotherapeutic response. BRMS1 + microglial cells provide a new perspective for a deeper understanding of the immunosuppressive microenvironment of GBM and could serve as a potential therapeutic target in the future.

Blebs promote cell survival by assembling oncogenic signalling hubs.

Most human cells require anchorage for survival. Cell-substrate adhesion activates diverse signalling pathways, without which cells undergo anoikis-a form of programmed cell death1. Acquisition of anoikis resistance is a pivotal step in cancer disease progression, as metastasizing cells often lose firm attachment to surrounding tissue2,3. In these poorly attached states, cells adopt rounded morphologies and form small hemispherical plasma membrane protrusions called blebs4-11. Bleb function has been thoroughly investigated in the context of amoeboid migration, but it has been examined far less in other scenarios12. Here we show by three-dimensional imaging and manipulation of cell morphological states that blebbing triggers the formation of plasma membrane-proximal signalling hubs that confer anoikis resistance. Specifically, in melanoma cells, blebbing generates plasma membrane contours that recruit curvature-sensing septin proteins as scaffolds for constitutively active mutant NRAS and effectors. These signalling hubs activate ERK and PI3K-well-established promoters of pro-survival pathways. Inhibition of blebs or septins has little effect on the survival of well-adhered cells, but in detached cells it causes NRAS mislocalization, reduced MAPK and PI3K activity, and ultimately, death. This unveils a morphological requirement for mutant NRAS to operate as an effective oncoprotein. Furthermore, whereas some BRAF-mutated melanoma cells do not rely on this survival pathway in a basal state, inhibition of BRAF and MEK strongly sensitizes them to both bleb and septin inhibition. Moreover, fibroblasts engineered to sustain blebbing acquire the same anoikis resistance as cancer cells even without harbouring oncogenic mutations. Thus, blebs are potent signalling organelles capable of integrating myriad cellular information flows into concerted cellular responses, in this case granting robust anoikis resistance.

FAM188B Downregulation Sensitizes Lung Cancer Cells to Anoikis via EGFR Downregulation and Inhibits Tumor Metastasis In Vivo.

Simple SummaryCancer cells should acquire anoikis resistance for successful metastasis. Family with sequence similarity 188 member B (FAM188B) has been identified as a new deubiquitinase (DUB) member. Here, we demonstrate that FAM188B knockdown makes lung cancer cells sensitive to anoikis and inhibits lung metastasis. FAM188B knockdown reduced the levels of tumor proteins such as EGFR and FOXM1, suggesting that FAM188B may be a potential target controlling tumor malignancies.Anoikis is a type of apoptosis induced by cell detachment from the extracellular matrix (ECM), which removes mislocalized cells. Acquisition of anoikis resistance is critical for cancer cells to survive during circulation and, thus, metastasize at a secondary site. Although the sensitization of cancer cells to anoikis is a potential strategy to prevent metastasis, the mechanism underlying anoikis resistance is not well defined. Although family with sequence similarity 188 member B (FAM188B) is predicted as a new deubiquitinase (DUB) member, its biological function has not been fully studied. In this study, we demonstrated that FAM188B knockdown sensitized anoikis of lung cancer cell lines expressing WT-EGFR (A549 and H1299) or TKI-resistant EGFR mutant T790M/L858R (H1975). FAM188B knockdown using si-FAM188B inhibited the growth of all three human lung cancer cell lines cultured in both attachment and suspension conditions. FAM188B knockdown resulted in EGFR downregulation and thus decreased its activity. FAM188B knockdown decreased the activities of several oncogenic proteins downstream of EGFR that are involved in anoikis resistance, including pAkt, pSrc, and pSTAT3, with little changes to their protein levels. Intriguingly, si-FAM188B treatment increased EGFR mRNA levels but decreased its protein levels, which was reversed by treatment with the proteasomal inhibitor MG132, indicating that FAM188B regulates EGFR levels via the proteasomal pathway. In addition, cells transfected with si-FAM188B had decreased expression of FOXM1, an oncogenic transcription factor involved in cell growth and survival. Moreover, FAM188B downregulation reduced metastatic characteristics, such as cell adhesion, invasion, and migration, as well as growth in 3D culture conditions. Finally, tail vein injection of si-FAM188B-treated A549 cells resulted in a decrease in lung metastasis and an increase in mice survival in vivo. Taken together, these findings indicate that FAM188B plays an important role in anoikis resistance and metastatic characteristics by maintaining the levels of various oncogenic proteins and/or their activity, leading to tumor malignancy. Our study suggests FAM188B as a potential target for controlling tumor malignancy.

Detection of Anoikis Using Cell Viability Dye and Quantitation of Caspase Activity.

Anoikis is a type of programmed cell death triggered by the loss of cellular interaction with the extracellular matrix (ECM) and culminates in the activation of caspases. Specific interaction between cellular receptors such as integrins and the ECM is important to maintain cellular homeostasis in normal tissues through multiple cascades. This interaction provides not only physical attachment, but more importantly, vital interaction with the actin cytoskeleton and growth factors. Normal epithelial and endothelial cells require this interaction with ECM to survive. In cancer, the acquisition of anoikis resistance is a hallmark of malignant transformation and is required in the process of metastasis formation. As such, strategies to inhibit and/or counteract anoikis resistance areimportant in controlling cancer progression. In this chapter, we describe the method for detecting anoikis using cell viability and caspase activity assays.

Proteomic Analysis of the Anoikis-Resistant Human Breast Cancer Cell Lines.

Acquisition of anoikis resistance is a prerequisite for cancer metastasis and invasion, which are major causes of death from cancer. The molecular mechanisms underlying antianoikis properties in cancer cells are still largely unclear. Here, we describe a protocol for preparation of anoikis-resistant cultured nonmetastatic MCF-7 and metastatic MDA-MB-231 cell lines. The anoikis-resistant cultures were prepared by plating cells in the poly-2-hydroxyethyl methacrylate coated plates and cultured for 24h. The viability of cells in the cultures was determined using trypan blue staining and annexin V cell death assay, while protein profiles associated with anoikis-resistance in both cells and conditioned media were analyzed by proteomics.

Caveolin‐1 contributes to anoikis resistance in human gastric cancer SGC‐7901 cells via regulating Src‐dependent EGFR‐ITGB1 signaling

Anoikis resistance is considered to be an essential prerequisite of tumor metastasis and which is an important mechanism in the metastatic process of gastric cancer (GC). Caveolin-1 (CAV-1), a protein component of caveolae, has been reported to regulate several cancer cell behaviors including anoikis resistance. However, the role of CAV-1 in the acquisition of anoikis resistance in GC cells has never been explored. In this study, we investigated the promoting effect of CAV-1 on anchorage-independent growth and anoikis resistance, and the involvement of the related signaling pathways in such process in SGC-7901 cells. The results showed that CAV-1 could promote anchorage-independent growth and anoikis resistance in detached SGC-7901 cells, which was associated with the activation of Src-dependent epidermal growth factor receptor-integrin β signaling as well as the phosphorylation of PI3K/Akt and MEK/ERK signaling pathways. The data from this study might contribute to the in-depth understanding of the metastatic mechanism for GC.

Tubeimoside V sensitizes human triple negative breast cancer MDA-MB-231 cells to anoikis via regulating caveolin-1-related signaling pathways

Metastatic triple-negative breast cancer (TNBC) has poor outcome with conventional chemotherapy regimens due to its aggressive behavior. The acquisition of anoikis resistance, a programmed cell death process triggered by substratum detachment, is an important mechanism in TNBC metastasis. Therefore, agents that can restore the sensitivity of cancer cells to anoikis may be helpful for the treatment of metastatic TNBC. In this study, we investigated the inhibitory effect of Tubeimosides V (TBMS-V), a cyclic bisdesmoside isolated from the ethanol extracts of tubers of B. paniculatum., on anoikis resistance and the involvement of caveolin-1(CAV-1)-related signaling pathways in such process in MDA-MB-231 cells. The results showed that the treatment of TBMS-V could sensitize cancer cells to anoikis, which was associated with suppression of anchorage-independent culture-induced CAV-1 overexpression, EGFR activation as well as ITGB1-FAK activation. The data from this study might contribute to providing a potential therapeutic target for metastatic TNBC and suggest the possibility of TBMS-V and its derivatives for metastatic TNBC therapy.

STAT3 mediates resistance to anoikis and promotes invasiveness of nasopharyngeal cancer cells.

Nasopharyngeal carcinoma (NPC), a tumor arising from the epithelial cells of the nasopharynx, is endemic in Southeast Asia and Taiwan. The prognosis of NPC patients with local recurrence and metastasis is poor. Resistance to anoikis is a primary characteristic of tumor cells that metastasize. However, the mechanism through which NPC cells resist anoikis and are able to metastasize has not been fully elucidated. In the present study, the acquisition of anoikis resistance was analyzed in the TW01 and TW06 human NPC cell lines growing under anchorage-independent conditions. A considerable number of TW01 and TW06 cells was found to be resistant to anoikis and exhibited a higher capability of migration and invasion. These anoikis-resistant NPC cells exhibited significantly increased expression of signal transducer and activation of transcription3 (Stat3) compared with adherent cells. Furthermore, blockade of STAT3 expression by STAT3 inhibitors or STAT3 silencing significant increased anoikis in anoikis-resistant NPC cells. Moreover, silencing STAT3 not only reduced the capacity of NPC cells to resist anoikis, but also reversed their invasive properties. The expression of epithelial‑to-mesenchymal transition‑related proteins and CD44 was also significantly decreased following STAT3 knockdown. The results of the present study established that STAT3 mediates anoikis resistance, with enhanced cell migration and invasion of NPC cells, and that activation of STAT3 may increase metastatic capacity, indicating the crucial role of STAT3 in conferring anoikis resistance and enhanced invasive properties to NPC cells.

Exosomes secreted from human colon cancer cells influence the adhesion of neighboring metastatic cells: Role of microRNA-210

ABSTRACTCancer-secreted exosomes influence tumor microenvironment and support cancer growth and metastasis. MiR-210 is frequently up-regulated in colorectal cancer tissues and correlates with metastatic disease. We investigated whether exosomes are actively released by HCT-8 colon cancer cells, the role of exosomal miR-210 in the cross-talk between primary cancer cells and neighboring metastatic cells and its contribution in regulating epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET).After 7 d of culture, a subpopulation of viable HCT-8 cells detached the monolayer and started to grow in suspension, suggesting anoikis resistance and a metastatic potential. The expression of key proteins of EMT revealed that these cells were E-cadherin negative and vimentin positive further confirming their metastatic phenotype and the acquisition of anoikis resistance. Metastatic cells, in the presence of adherently growing HCT-8, continued to grow in suspension whereas only if seeded in cell-free wells, were able to adhere again and to form E-cadherin positive and vimentin negative new colonies, suggesting the occurrence of MET.The chemosensitivity to 5 fluorouracil and to FOLFOX-like treatment of metastatic cells was significantly diminished compared to adherent HCT-8 cells. Of note, adherent new colonies undergoing MET, were insensitive to both chemotherapeutic strategies. Electron microscopy analysis demonstrated that adherently growing HCT-8, actually secreted exosomes and that exosomes in turn were taken up by metastatic cells. When exosomes secreted by adherently growing HCT-8 were administered to metastatic cells, MET was significantly inhibited. miR-210 was significantly upregulated in exosomes compared to its intracellular levels in adherently growing HCT-8 cells and correlated to anoikis resistance and EMT markers.Exosomes containing miR-210 might be considered as EMT promoting signals that preserve the local cancer-growth permissive milieu and also guide metastatic cells to free, new sites of dissemination.

Anoikis-resistant cholangiocarcinoma cells display aggressive characteristics and increase STAT3 activation.

Anoikis is a specialized cell apoptosis triggered by loss of cell adhesion. Acquisition of anoikis resistance is a key cancer hallmark that has been associated with metastasis of human malignancies. Cholangiocarcinoma (CCA) is a highly metastatic cancer of the bile duct, in which mechanisms underlying its resistance to anoikis has not been well elucidated. HuCCT1 and Huh28 were utilized as in vitro models to examine biological characteristics of anoikis resistant-CCA cells. Expression and activation of signaling molecules were determined by western blotting. We demonstrated that a significant proportion of CCA cells including HuCCT1 and Huh28 resisted anoikis induced by anchorage-independent condition. Notably, anoikis-resistant CCA cells, especially HuCCT1, substantially increased invasive potential and became resistant to gemcitabine, which is the standard chemotherapeutic agent for CCA. Mechanistically, the anoikis-resistant HuCCT1 cells markedly increased activation of signal transducer and activator of transcription 3 (STAT3) and concomitantly upregulated anti-apoptotic proteins, Mcl-1 and Bcl-2. Inhibition of STAT3 by AG 490 significantly induced HuCCT1 cells to undergo anoikis. Taken together, our findings uncover the aggressive properties of CCA cells that overcome anoikis, and reveal the involvement of STAT3 signaling pathway in anoikis resistance in CCA. Targeting STAT3 may restore anoikis and prevent metastasis of the disease.

RETRACTED ARTICLE: Mechanistic attributes of S100A7 (psoriasin) in resistance of anoikis resulting tumor progression in squamous cell carcinoma of the oral cavity

BackgroundSquamous cell carcinoma of the oral cavity (SCCOC) is the dominant origin of cancer associated mortality. Previous findings by our study reported that acquisition of anoikis resistance has a significant role in tumor progression of oral cavity. Several genes were over-expressed in anoikis-resistant cells under detached conditions which we confirmed earlier by microarray. Normal oral squamous epithelia grow adherent to a basement membrane, and when detached from the extracellular matrix, undergoes programmed cell death. The acquisition of anoikis-resistance is crucial phenomena in oral tumor advancement. In the current study, we have identified S100A7 expression as contributing factor for anoikis resistance and tumorigenicity in human oral cancer cells. Further, we have explored that elevated S100A7 expression in anoikis-sensitive oral keratinocytes and cancer cells reshape them more resistant to anoikis and apoptosis inducers via activation of cellular intrinsic and extrinsic avenue.MethodsA subset of human cancer cell lines TU167, JMAR, JMARC39, JMARC42 and MDA-MB-468 were utilized for the generation of resistant stable cell lines. Further, immunohistochemistry, western blot and immunoprecipitation, assays of apoptosis, soft agar assay, orthotopic animal model and signaling elucidation were performed to establish our hypothesis.ResultsS100A7 gene is found to be responsible for anoikis resistance and tumorigenicity in human oral cancer cells. We have observed up-regulation of S100A7 in anoikis resistant cell lines, orthotropic model and patients samples with head and neck cancer. It is also noticed that secretion of S100A7 protein in conditioned medium by anoikis resistant head & neck cancer cell and in saliva of head and neck cancer patients. Up-regulation of S100A7 expression has triggered enhanced tumorigenicity and anchorage-independent growth of cancer cells through Akt phosphorylation leading to development of aniokis resistance in head and neck cancer cells.ConclusionsThese data have led us to conclude that S100A7 is the major contributing factor in mediating anoikis-resistance of oral cancer cells and local tumor progression, and S100A7 might be useful as diagnostic marker for early detection of primary and recurrent squamous cell cancer.

Acquisition of anoikis resistance up-regulates syndecan-4 expression in endothelial cells.

Anoikis is a programmed cell death induced upon cell detachment from extracellular matrix, behaving as a critical mechanism in preventing adherent-independent cell growth and attachment to an inappropriate matrix, thus avoiding colonization of distant organs. Cell adhesion plays an important role in neoplastic transformation. Tumors produce several molecules that facilitate their proliferation, invasion and maintenance, especially proteoglycans. The syndecan-4, a heparan sulfate proteoglycan, can act as a co-receptor of growth factors and proteins of the extracellular matrix by increasing the affinity of adhesion molecules to their specific receptors. It participates together with integrins in cell adhesion at focal contacts connecting the extracellular matrix to the cytoskeleton. Changes in the expression of syndecan-4 have been observed in tumor cells, indicating its involvement in cancer. This study investigates the role of syndecan-4 in the process of anoikis and cell transformation. Endothelial cells were submitted to sequential cycles of forced anchorage impediment and distinct lineages were obtained. Anoikis-resistant endothelial cells display morphological alterations, high rate of proliferation, poor adhesion to fibronectin, laminin and collagen IV and deregulation of the cell cycle, becoming less serum-dependent. Furthermore, anoikis-resistant cell lines display a high invasive potential and a low rate of apoptosis. This is accompanied by an increase in the levels of heparan sulfate and chondroitin sulfate as well as by changes in the expression of syndecan-4 and heparanase. These results indicate that syndecan-4 plays a important role in acquisition of anoikis resistance and that the conferral of anoikis resistance may suffice to transform endothelial cells.

Retraction: Epithelial mesenchymal transition is required for acquisition of anoikis resistance and metastatic potential in adenoid cystic carcinoma.

Retraction: Epithelial mesenchymal transition is required for acquisition of anoikis resistance and metastatic potential in adenoid cystic carcinoma.

Identification of a novel AMPK-PEA15 axis in the anoikis-resistant growth of mammary cells.

IntroductionMatrix detachment triggers anoikis, a form of apoptosis, in most normal epithelial cells, while acquisition of anoikis resistance is a prime requisite for solid tumor growth. Of note, recent studies have revealed that a small population of normal human mammary epithelial cells (HMECs) survive in suspension and generate multicellular spheroids termed ‘mammospheres’. Therefore, understanding how normal HMECs overcome anoikis may provide insights into breast cancer initiation and progression.MethodsPrimary breast tissue-derived normal HMECs were grown as adherent monolayers or mammospheres. The status of AMP-activated protein kinase (AMPK) and PEA15 signaling was investigated by immunoblotting. Pharmacological agents and an RNA interference (RNAi) approach were employed to gauge their roles in mammosphere formation. Immunoprecipitation and in vitro kinase assays were undertaken to evaluate interactions between AMPK and PEA15. In vitro sphere formation and tumor xenograft assays were performed to understand their roles in tumorigenicity.ResultsIn this study, we show that mammosphere formation by normal HMECs is accompanied with an increase in AMPK activity. Inhibition or knockdown of AMPK impaired mammosphere formation. Concomitant with AMPK activation, we detected increased Ser116 phosphorylation of PEA15, which promotes its anti-apoptotic functions. Inhibition or knockdown of AMPK impaired PEA15 Ser116 phosphorylation and increased apoptosis. Knockdown of PEA15, or overexpression of the nonphosphorylatable S116A mutant of PEA15, also abrogated mammosphere formation. We further demonstrate that AMPK directly interacts with and phosphorylates PEA15 at Ser116 residue, thus identifying PEA15 as a novel AMPK substrate. Together, these data revealed that AMPK activation facilitates mammosphere formation by inhibition of apoptosis, at least in part, through Ser116 phosphorylation of PEA15. Since anoikis resistance plays a critical role in solid tumor growth, we investigated the relevance of these findings in the context of breast cancer. Significantly, we show that the AMPK-PEA15 axis plays an important role in the anchorage-independent growth of breast cancer cells both in vitro and in vivo.ConclusionsOur study identifies a novel AMPK-PEA15 signaling axis in the anchorage-independent growth of both normal and cancerous mammary epithelial cells, suggesting that breast cancer cells may employ mechanisms of anoikis resistance already inherent within a subset of normal HMECs. Thus, targeting the AMPK-PEA15 axis might prevent breast cancer dissemination and metastasis.Electronic supplementary materialThe online version of this article (doi:10.1186/s13058-014-0420-z) contains supplementary material, which is available to authorized users.

Upregulation of BNIP3 mediated by ERK/HIF-1α pathway induces autophagy and contributes to anoikis resistance of hepatocellular carcinoma cells.

Acquisition of anoikis resistance is the hallmark of cancer and has been shown to be involved in metastasis of melignant cells. Our previous work showed that anoikis resistance is associated with the metastasis of hepatocellular carcinoma (HCC) cells. The aim of this study is to elucidate the mechanisms of this course. Expression of BNIP3 and HIF-1α at the mRNA and protein level in HCC cells were detected by realtime PCR and western blot, respectively. Autophagy activation and signaling transduction pathway were detected by western blot. Cell viabilities were detected by CCK8 assay and trypan blue exclusion assay. Upregulation of BNIP3 promoted the activation of autophagy, one type of cell survival strategy in response to external stress, by suppressing mTOR/S6K1 signaling system. The upregulation of BNIP3 was mediated by ERK/HIF-1α pathway, which further contributed to anoikis resistance of HCC cells through the mTORC1 signaling pathway. Upregulation of BNIP3 contributs to anoikis resistance of HCC cells, and BNIP3 may serve as a novel therapeutic target for manipulation of cancer metastasis.

Novel small RNA expression libraries uncover hsa-miR-30b and hsa-miR-30c as important factors in anoikis resistance

MicroRNAs (miRNAs) have been widely studied in order to elucidate their biological functions. MicroRNA microarrays or miRNA overexpression libraries generated by synthesis and cloning of individual miRNAs have been used to study their different roles. In this work, we have developed a novel methodology to express mature miRNAs and other small RNAs from a double convergent RNA polymerase III promoter. We show that the generated miRNAs function similarly to those processed from primary transcripts or pri-miRNAs. This system allowed us to produce a lentiviral library expressing the whole population of small RNAs present in a metastatic cell line. A functional screening using this library led to the identification of hsa-miR-30b and hsa-miR-30c as negative regulators of cell death induced by loss of attachment (anoikis). Importantly, we demonstrated that the acquisition of anoikis resistance via these miRNAs is achieved through down-regulation of caspase 3 expression. Moreover, overexpression of these miRNAs resulted in a decrease of other types of caspase 3-dependent cell death and enhanced the survival of MCF10A acinar cells in morphogenesis assays, suggesting a putative role as oncomirs. In summary, this novel methodology provides a powerful and effective way for identifying novel small RNAs involved in a particular biological process.

Abstract 4131: Alternative splicing changes during the acquisition of anoikis resistance.

Abstract Breast cancer is the most common cancer in women and the second leading cause of cancer-related death among women in the U.S. Metastases from the primary tumor are common and are the main cause of mortality in this population. Therefore, it is imperative to identify therapeutic molecules that target mechanisms specific to metastatic cells. One such mechanism to target is anoikis, a specialized form of programmed cell death that prevents epithelial cells shed from basement membranes from colonizing distant organs. Circulating tumor cells (CTCs) become anoikis-resistant, which is an essential early step in the development of distant metastases in many types of cancer including breast cancer. Recent studies have implicated RNA splicing dysregulation in a number of cancer phenotypes (e.g. oncogenesis). In these studies, we have developed anoikis-resistant (AnR) breast cancer cell lines, which grow unattached to hydrophilic surfaces. We then performed a preliminary intron / exon array screen comparing parental and AnR breast cancer cell lines. This approach identified a novel splice variant of Non-catalytic region of tyrosine kinase associated protein 1 (NckAP1), in which the 15-18 cassette is deleted. This splice variant is dysregulated in both AnR cells and in relevant samples from breast cancer patients. NckAP1, along with Nck and Ras-related C3 botulinum toxin substrate (Rac), are found in a complex with the actin-polymerization protein Wiskott Aldrich syndrome protein verprolin homologous 1 (WAVE1). After dissociation from this complex, WAVE1 is able to induce polymerization of actin during lamellipodia formation, and is thus a mediator of migration. Hence, splicing of NckAP1 may help mediate migratory capacity of breast cancer cells. These studies also suggest a major role for splicing regulation in metastasis. Citation Format: Quoc Huynh, Charles E. Chalfant, Margaret A. Park. Alternative splicing changes during the acquisition of anoikis resistance. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4131. doi:10.1158/1538-7445.AM2013-4131

Abstract 4043: The role of CD63/Timp1/β1 integrin complex in cell survival.

Abstract Although malignant melanoma is the less frequently diagnosed skin cancer, it shows a poor prognosis due its chemoresistance and metastasis development. One of the acquired abilities of transformed cells is anoikis resistance and this property is closely related to metastasis formation. In our laboratory, we developed a model that allows us to study different steps of melanocyte malignant transformation. Melan-a melanocytes surviving after 1, 2, 3 and 4 deadhesion cycles showed modified morphology and independent PMA growth and have been named 1C, 2C, 3C and 4C cells, respectively. Different melanoma cell lines were established after submitting 4C spheroids to limiting dilution. Previous data from our group demonstrated increased expression of Timp1 and resistance to anoikis during the malignant transformation of melanocytes. Melan-a melanocytes overexpressing Timp1 acquire anoikis-resistant phenotype. In our laboratory, we observed interaction between CD63, Timp1 and β1-integrin in the 4C, 4C11- and 4C11+ cell lines established after cycles of anchorage impediment. This seems to be the first study describing the interaction between Timp1, CD63 and β1-integrin in tumor cells. However, it is unclear how Timp1 modulates resistance to anoikis. Therefore, our aim is to analyze the role of Timp1 in the context of Timp1/CD63/β1-integrin complex and the signaling pathways involved in the acquisition of anoikis resistance. Supported by CAPES and FAPESP. Citation Format: Mariana T. Pinto, Fabiana Henriques Machado de Melo, Miriam Galvonas Jasiulionis. The role of CD63/Timp1/β1 integrin complex in cell survival. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4043. doi:10.1158/1538-7445.AM2013-4043

Abstract 2081: Mechanisms of the acquisition of anoikis resistance in breast cancer: Lessons from small molecule inhibitors

Abstract The Cox-2 inhibitor Celecoxib has been reported to possess chemopreventive and chemotherapeutic properties, specifically in hormonally-regulated tumors. OSU-03012 is a novel celecoxib derivative, with no COX-2 inhibitory activity, but an order of magnitude greater cell killing ability. We here show that this novel compound has a greater cytotoxicity against a model of anoikis-resistant (AnR) breast cancer. In parallel, anoikis resistance reduces AnR cell sensitivity to the ErbB1/2 dual inhibitor Lapatinib (GW572016, Tykerb, GSK). The two compounds synergize in parental breast cancer cells. Cell killing is achieved partially via induction of ER stress, as measured by eIF2-alpha phosphorylation. We have found that lapatinib resistance may be induced by the aberrant splicing of BCL-X, and that the sensitivity to OSU-03012 is likely due to PTEN dysregulation. In conclusion, these data identify a molecule that may be more efficacious against metastatic tumors, and partially defined its mechanism of action. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2081. doi:1538-7445.AM2012-2081

Acquisition of anoikis resistance through CD147 upregulation: A new mechanism underlying metastasis of hepatocellular carcinoma cells

Acquisition of anoikis resistance is a prerequisite for the metastasis of hepatocellular carcinoma (HCC) cells. Activation of growth factor signaling pathways and rearrangement of the cytoskeleton have been reported as vital steps in this process. However, key molecules involved in anoikis resistance remain to be determined. The aim of this study was to investigate the effect of CD147 on HCC cells resistant to anoikis. The human SMMC-7221 human HCC cell line was used. Immunofluorescence was used to investigate the expression levels of CD147. Anoikis-induced cell death was assessed using trypan blue exclusion. In the present study, the results showed that SMMC-7721 HCC cells exhibited significant morphological changes when suspended in culture medium supplemented with 1% methocel and a subpopulation of cells resistant to anoikis was acquired with higher viability and invasion ability. CD147 was identified to be significantly increased in cells resistant to anoikis, when compared to the parental cells. CD147 knockdown by siRNA notably induced cell anoikis, partially through the inactivation of PI3K/Akt pathway. All of these evidence provide a novel CD147-related mechanism underlying the metastasis of HCC cells.