Anchorage-independent Spheroid Research Articles

Sec23a inhibits the self-renewal of melanoma cancer stem cells via inactivation of ER-phagy

BackgroundThe genesis and developments of solid tumors, analogous to the renewal of healthy tissues, are driven by a subpopulation of dedicated stem cells, known as cancer stem cells (CSCs), that exhibit long-term clonal repopulation and self-renewal capacity. CSCs may regulate tumor initiation, growth, dormancy, metastasis, recurrence and chemoresistance. While autophagy has been proposed as a regulator of the stemness of CSCs, the underlying mechanisms requires further elucidation.MethodsThe CSC component in human melanoma cell lines M14 and A375 was isolated and purified by repetitive enrichments for cells that consistently display anchorage-independent spheroid growth. The stemness properties of the CSCs were confirmed in vitro by the expressions of stemness marker genes, the single-cell cloning assay and the serial spheroid formation assay. Subcutaneous tumor transplantation assay in BALB/c nude mice was performed to test the stemness properties of the CSCs in vivo. The autophagic activity was confirmed by the protein level of LC3 and P62, mRFP-LC3B punta and cytoplasmic accumulation of autolysosomes. The morphology of ER was detected with transmission electron microscopy.ResultsIn the present study, by employing stable CSC cell lines derived from human melanoma cell lines M14 and A375, we show for the first time that Sec23a inhibits the self-renewal of melanoma CSCs via inactivation of ER-phagy. Mechanistically, inhibition of Sec23a reduces ER stress and consequently FAM134B-induced ER-phagy. Furthermore, TCGA data mining and analysis show that Sec23a is a favorable diagnostic and prognostic marker for human skin cutaneous melanoma.ConclusionThis study has elucidated a new mechanism underlying the regulation of autophagy on stemness, i.e. CSCs can exploit the SEC23A/ER-stress/FAM134B/ER-phagy axis for the self-renewal. These observations provide new ideas for exploration of the regulatory network of CSC self-renewal to develop CSCs-based therapy strategies for malignant tumors.1GUvTquPwXFE-w4yWuDKxrVideo

Optimization of Extracellular Flux Assay to Measure Respiration of Anchorage-independent Tumor Cell Spheroids.

Three-dimensional (3D) cell culture models are widely used in tumor studies to more accurately reflect cell-cell interactions and tumor growth conditions in vivo. 3D anchorage-independent spheroids derived by culturing cells in ultra-low attachment (ULA) conditions is particularly relevant to ovarian cancer, as such cell clusters are often observed in malignant ascites of late-stage ovarian cancer patients. We and others have found that cells derived from anchorage-independent spheroids vary widely in gene expression profiles, proliferative state, and metabolism compared to cells maintained under attached culture conditions. This includes changes in mitochondrial function, which is most commonly assessed in cultured live cells by measuring oxygen consumption in extracellular flux assays. To measure mitochondrial function in anchorage-independent multicellular aggregates, we have adapted the Agilent Seahorse extracellular flux assay to optimize measurements of oxygen consumption and extracellular acidification of ovarian cancer cell spheroids generated by culture in ULA plates. This protocol includes: (i) Methods for culturing tumor cells as uniform anchorage-independent spheroids; (ii) Optimization for the transfer of spheroids to the Agilent Seahorse cell culture plates; (iii) Adaptations of the mitochondrial and glycolysis stress tests for spheroid extracellular flux analysis; and (iv) Suggestions for optimization of cell numbers, spheroid size, and normalization of oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) values. Using this method, we have found that ovarian cancer cells cultured as anchorage-independent spheroids display altered mitochondrial function compared to monolayer cultures attached to plastic dishes. This method allows for the assessment of mitochondrial function in a more relevant patho/physiological culture condition and can be adapted to evaluate mitochondrial function of various cell types that are able to aggregate into multicellular clusters in anchorage-independence. Graphic abstract: Workflow of the Extracellular Flux Assay to Measure Respiration of Anchorage-independent Tumor Cell Spheroids.

A liquid culture cancer spheroid model reveals low PI3K/Akt pathway activity and low adhesiveness to the extracellular matrix.

Three-dimensional (3D) cultures of cancer cells in liquid without extracellular matrix (ECM) offer invitro models for metastasising conditions such as those in vessels and effusion. However, liquid culturing is often hindered by cell adhesiveness, which causes large cell clumps. We previously described a liquid culture material, LA717, which prevents nonclonal cell adhesion and subsequent clumping, thus allowing clonal growth of spheroids in an anchorage-independent manner. Here, we examined such liquid culture cancer spheroids for the acquisition of apical-basal polarity, sensitivity to an Akt inhibitor (anticancer drug MK-2206) and interaction with ECM. The spheroids present apical plasma membrane on the surface, which originated from the failure of polarisation at the single-cell stage and subsequent defects in phosphorylated ezrin accumulation at the cell boundary during the first cleavage, failing internal lumen formation. At the multicellular stage, liquid culture spheroids presented bleb-like protrusion on the surface, which was enhanced by the activation of the PI3K/Akt pathway and reduced by PI3K/Akt inhibitors. Liquid culture spheroids exhibited slow proliferation speed and low endogenous pAkt levels compared with gel-cultured spheroids and 2D-cultured cells, explaining the susceptibility to the Akt-inhibiting anticancer drug. Subcutaneous xenografting and invitro analysis demonstrated low viability and adhesive property of liquid culture spheroids to ECM, while migratory and invasive capacities were comparable with gel-cultured spheroids. These features agree with the low efficacy of circulating tumour spheroids in the settling step of metastasis. This study demonstrates the feature of anchorage-independent spheroids and validates liquid cultures as a useful method in cancer spheroid research.

Chronic exposure to cadmium induces a malignant transformation of benign prostate epithelial cells

Epidemiological evidence suggests that cadmium (Cd) is one of the causative factors of prostate cancer, but the effect of Cd on benign prostatic hyperplasia (BPH) remains unclear. This study aimed to determine whether Cd exposure could malignantly transform BPH1 cells and, if so, to dissect the mechanism of action. We deciphered the molecular signaling responsible for BPH1 transformation via RNA-sequencing and determined that Cd induced the expression of zinc finger of the cerebellum 2 (ZIC2) in BPH1 cells. We noted Cd exposure increased ZIC2 expression in the Cd-transformed BPH1 cells that in turn promoted anchorage-independent spheroids and increased expression of stem cell drivers, indicating their role in stem cell renewal. Subsequent silencing of ZIC2 expression in transformed cells inhibited spheroid formation, stem cell marker expression, and tumor growth in nude mice. At the molecular level, ZIC2 interacts with the glioma-associated oncogene family (GLI) zinc finger 1 (GLI1), which activates prosurvival factors (nuclear factor NFκB, B-cell lymphoma-2 (Bcl2), as well as an X-linked inhibitor of apoptosis protein (XIAP)) signaling in Cd-exposed BPH1 cells. Conversely, overexpression of ZIC2 in BPH1 cells caused spheroid formation confirming the oncogenic function of ZIC2. ZIC2 activation and GLI1 signaling induction by Cd exposure in primary BPH cells confirmed the clinical significance of this oncogenic function. Finally, human BPH specimens had increased ZIC2 versus adjacent healthy tissues. Thus, we report direct evidence that Cd exposure induces malignant transformation of BPH via activation of ZIC2 and GLI1 signaling.

In vitro and in vivo characterization of stem-like cells from canine osteosarcoma and assessment of drug sensitivity

Cancer stem cell (CSC) self-renewing and drug resistance cause treatment failure and tumor recurrence. Osteosarcoma is an aggressive bone tumor characterized by biological and molecular heterogeneity, possibly dependent on CSCs. CSC identification in osteosarcoma and their efficient targeting are still open questions. Spontaneous canine osteosarcoma shares clinical and biological features with the human tumors, representing a model for translational studies. We characterized three CSC-enriched canine osteosarcoma cultures. In serum-free conditions, these CSC cultures grow as anchorage-independent spheroids, show mesenchymal-like properties and in vivo tumorigenicity, recapitulating the heterogeneity of the original osteosarcoma. Osteosarcoma CSCs express stem-related factors (Sox2, Oct4, CD133) and chemokine receptors and ligands (CXCR4, CXCL12) involved in tumor proliferation and self-renewal. Standard drugs for osteosarcoma treatment (doxorubicin and cisplatin) affected CSC-enriched and parental primary cultures, showing different efficacy within tumors. Moreover, metformin, a type-2 diabetes drug, significantly inhibits osteosarcoma CSC viability, migration and self-renewal and, in co-treatment with doxorubicin and cisplatin, enhances drug cytotoxicity. Collectively, we demonstrate that canine osteosarcoma primary cultures contain CSCs exhibiting distinctive sensitivity to anticancer agents, as a reliable experimental model to assay drug efficacy. We also provide proof-of-principle of metformin efficacy, alone or in combination, as pharmacological strategy to target osteosarcoma CSCs.

An Efficient and Flexible Cell Aggregation Method for 3D Spheroid Production.

Monolayer cell culture does not adequately model the in vivo behavior of tissues, which involves complex cell-cell and cell-matrix interactions. Three-dimensional (3D) cell culture techniques are a recent innovation developed to address the shortcomings of adherent cell culture. While several techniques for generating tissue analogues in vitro have been developed, these methods are frequently complex, expensive to establish, require specialized equipment, and are generally limited by compatibility with only certain cell types. Here, we describe a rapid and flexible protocol for aggregating cells into multicellular 3D spheroids of consistent size that is compatible with growth of a variety of tumor and normal cell lines. We utilize varying concentrations of serum and methyl cellulose (MC) to promote anchorage-independent spheroid generation and prevent the formation of cell monolayers in a highly reproducible manner. Optimal conditions for individual cell lines can be achieved by adjusting MC or serum concentrations in the spheroid formation medium. The 3D spheroids generated can be collected for use in a wide range of applications, including cell signaling or gene expression studies, candidate drug screening, or in the study of cellular processes such as tumor cell invasion and migration. The protocol is also readily adapted to generate clonal spheroids from single cells, and can be adapted to assess anchorage-independent growth and anoikis-resistance. Overall, our protocol provides an easily modifiable method for generating and utilizing 3D cell spheroids in order to recapitulate the 3D microenvironment of tissues and model the in vivo growth of normal and tumor cells.

Dietary Flavonoids Luteolin and Quercetin Suppressed Cancer Stem Cell Properties and Metastatic Potential of Isolated Prostate Cancer Cells.

A highly invasive Du145-III subline was isolated by three successive passages of the parental Du145 prostate tumor cell line (Du145-P) through a Boyden chamber with matrigel-coated membrane support. Du145-III cells showed great invasion potential based on their increased ability to spread/migrate and enhanced expression/secretion of the matrix metalloproteinase 9 (MMP9). Du145-III cells exerted vasculogenic mimicry (VM) properties, reminiscent of endothelial cell characteristics and expressed elevated levels of cancer stem cell (CSC) markers, including Nanog, Sox2, CD44 and ABCG2 and ability to self-renew. Of prominence, MMP9 was required for the induction of VM and for increased stemness in Du145-III cells. Using Du145-III as a model, the effects of dietary flavonoids, luteolin and quercetin, were evaluated on stemness and invasion capacity of Du145-III cells in relation to JNK signaling pathway activation. These flavonoids depressed the malignancy of highly invasive Du145-III cells, VM, anchorage-independent spheroid formation and expression of certain CSC markers. Since luteolin and quercetin were able to target CSC cells and prevent cancer cell invasiveness, may serve as potential anti-angiogenesis and anti-metastasis agents.

Abstract A12: Regulation of the mitochondrial stress response and metabolism by the intraperitoneal tumor environment during ovarian cancer transcoelomic metastasis

Abstract Transcoelomic metastasis represents one of the routes by which ovarian cancer cells colonize the omental tissues of the intraperitoneal (IP) cavity. Large quantities of viable tumor cells and spheroid aggregates can be isolated from ascites of advanced stage ovarian cancer patients, suggesting that cancer cells spend some time in anchorage independence under the physical and chemical influence of the IP tumor environment. Using ovarian cancer cell lines and patient ascites-derived tumor cells we demonstrate that levels of the mitochondrial stress response proteins, superoxide dismutase 2 (Sod2) and the deacetylase sirtuin 3 (SIRT3), are significantly increased when cultured in anchorage independent conditions, where cells rapidly form spheroid aggregates. Mimicking the ascites fluid current we show that expression of these proteins is further enhanced when spheroids are exposed to sheer forces, suggesting that the physical environment influences cellular stress adaptation. Presently, the combination of these physical cues and chemical stimuli emanating from ascites fluid are being interrogated in the co-regulation of the above mitochondrial proteins, focusing on the role of redox modulators and metabolite composition of ascites. It is our hypothesis that this stress response adaptation not only aids survival of cells in anchorage independence, but that it also drives a metabolic regulatory switch. Anchorage independent spheroids display a slowing in glycolysis and an increase in mitochondrial respiratory reserve capacity, as assessed by extracellular flux analysis. Sod2 expression is required for maintaining this mitochondrial respiratory function by scavenging damaging superoxide anion. Further, we observe decreases in global and mitochondrial acetylation, suggesting that deacetylase activity may be increased in spheroids. SIRT3 is a direct regulator of Sod2 activity, and is an important sensor of nutrient stress and modulator of metabolism, including the stimulation of fatty acid oxidation by deacetylation and activation of long-chain-specific acyl-CoA dehydrogenase. It has previously been demonstrated that metastatic ovarian cancer cells rely on fatty acid oxidation given their propensity to colonize the lipid-rich environments of the omentum. Studies are under way to test the hypothesis that SIRT3 expression stimulated by the IP tumor environment during anchorage independence primes ovarian cancer cells for fatty acid oxidation and is a necessary step before the colonization of the omentum. Citation Format: Dong-Hui Shin, Victoria Jones, Sara Shimko, Usawadee Dier, Trevor Shepherd, Timmins Patrick, Nadine Hempel. Regulation of the mitochondrial stress response and metabolism by the intraperitoneal tumor environment during ovarian cancer transcoelomic metastasis. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Metastasis; 2015 Nov 30-Dec 3; Austin, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(7 Suppl):Abstract nr A12.

Abstract 1440: Mitochondrial superoxide dismutase (Sod2) modulates ovarian clear cell carcinoma transcoelomic metastatic pathway

Abstract Ovarian clear cell carcinoma (OCCC) is a highly aggressive histological subtype that represents approximately 10% of all ovarian cancer cases and displays high expression of mitochondrial superoxide dismutase (Sod2), a major mitochondrial antioxidant enzyme. In the female body ovarian cancer cells metastasize via the transcoelomic route, where cells detach from the primary tumor into the intraperitoneal (IP) cavity and survive as unattached single cells or spheroid aggregates until they get carried via ascites fluid to the omental wall and surrounding organs for metastatic colonization. Ovarian cancer spheroids evade anoikis and display strong resistant to most anti-proliferative cancer drugs. This may contribute to the high recurrence rate and chemoresistance of ovarian cancer. The present study suggests that Sod2 is critically important for the key events of this transcoelomic metastatic route of OCCC. Levels of Sod2 are further increased in OCCC cell lines when these are cultured as anchorage-independent spheroid aggregates, suggesting that Sod2 may play a major role in spheroid stability and survival. When Sod2 levels are reduced using RNA interference, spheroid morphology of ES-2 OCCC cell line is compromised, suggesting a potential correlation between anoikis resistant and Sod2 levels in OCCC. Sod2 knockdown compromises mitochondrial metabolism, as a consequence of reduced superoxide scavenging, and enhances spheroid sensitivity to cisplatin. In addition, Sod2 is necessary for spheroid attachment and outgrowth on extracellular matrix components, representing the invasion of spheroids into the omental wall. Further, tumor cell metastasis is attenuated with reduced Sod2 levels when ES-2 spheroids are placed on the vasculature of the Chorioallantoic membrane (CAM). Scavenging H2O2 by exogenous addition of catalase inhibits the migration of OCCC and our data suggest that high levels of Sod2 in OCCC shift the intracellular redox balance to drive H2O2-dependent pro-metastatic signaling. These results indicate that Sod2 plays a major role in OCCC tumor metastasis, by regulating survival and chemoresistance of tumor spheroids in the IP cavity and by supporting attachment and migration at secondary metastatic sites. Inhibition of Sod2 can be a potential therapeutic target against OCCC transcoelomic metastasis. Citation Format: L.P.Madhubhani P. Hemachandra, Usawadee Dier, Nadine Hempel. Mitochondrial superoxide dismutase (Sod2) modulates ovarian clear cell carcinoma transcoelomic metastatic pathway. [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 1440. doi:10.1158/1538-7445.AM2015-1440

FAK activity protects nucleostemin in facilitating breast cancer spheroid and tumor growth

IntroductionFocal adhesion kinase (FAK) controls cell growth and survival downstream of integrin-matrix receptors. Upon adhesion loss or FAK inhibition, FAK can translocate to the nucleus. The nucleolus is a non-membrane nuclear structure that regulates ribosome biogenesis and cell proliferation. Nucleostemin (NS), a nucleolar-localized protein, modulates cell cycle progression, stemness, and three-dimensional tumor spheroid formation. The signaling pathways that regulate NS levels in tumors remain undefined.MethodsHuman breast carcinoma cells were evaluated for growth in culture (adherent and anchorage-independent spheroid) and as orthotopic tumors. FAK signaling was evaluated by pharmacological FAK inhibitor addition (PF-271, IC50 ~ 0.1 μM) and by small hairpin RNA (shRNA) knockdown followed by re-expression of FAK wildtype (WT) or a kinase-dead (KD, K454R) FAK point mutant. Immunoblotting was used to evaluate FAK, NS, nucleolar phosphoprotein B23, and nucleolin levels. Total and phosphospecific antibody imunoblotting were used to detect changes in FAK, Akt kinase (Akt also known as protein kinase B), and 4E-binding protein 1 (4E-BP1) phosphorylation, a translation repressor protein and target of the mammalian target of rapamycin (mTOR) complex. Immunohistochemical, co-immunoprecipitation, and cellular fractionation analyses were used to evaluate FAK association with nucleoli.ResultsPharmacological (0.1 μM PF-271) or genetic inhibition of FAK activity prevents MDA-MB-231 and 4T1L breast carcinoma growth as spheroids and as orthotopic tumors. FAK inhibition triggers proteasome-mediated decreased NS levels but no changes in other nucleolar proteins such as B23 (nucleophosmin) or nucleolin. Active FAK was associated with purified nucleoli of anchorage-independent cells and present within nucleoli of human invasive ductal carcinoma tumor samples. FAK co-immunoprecipitated with B23 that binds NS and a complex between FAK, NS, Akt, and mTOR was detected. Constitutively-active Akt kinase promoted tumor spheroid growth, stabilized NS levels, and promoted pS65 4E-BP1 phosphorylation in the presence of inhibited FAK. Rapamycin lowered NS levels and inhibited pS65 4E-BP1 phosphorylation in cells with activated Akt-mTOR signaling.ConclusionsFAK signaling occurs in the nucleolus, active FAK protects NS, and Akt-mTOR pathway regulates NS protein stability needed for breast carcinoma spheroid and tumor growth.Electronic supplementary materialThe online version of this article (doi:10.1186/s13058-015-0551-x) contains supplementary material, which is available to authorized users.

Abstract B69: Preferential transfer of mitochondria from endothelial to cancer cells through tunneling nanotubes modulates chemoresistance

Abstract Our vision of cancer has changed during the past decades. Indeed tumors are now perceived as complex entities where tumoral and stromal components interact closely. Among the different elements of tumor stroma the cellular component play a primordial role. Bone Marrow derived mesenchymal cells (MSCs) are attracted to tumor sites and support tumor growth. Endothelial cells (ECs) play a major role in angiogenesis. While the literature documents many aspects of the cross talk between stromal and cancer cells, the role of direct hetero-cellular contact is not clearly established. Recently, Tunneling nanotubes (TnTs) have been shown to support cell-to-cell transfers of plasma membrane components, cytosolic molecules and organelles within cell lines. Herein, we have investigated the formation of heterocellular TnTs between stromal (MSCs and ECs) and cancer cells. We demonstrate that TnTs occur between different cancer cells, stromal cells and cancer-stromal cell lines. We showed that TnTs-like structure occurred in 3D anchorage independent spheroids and also in tumor explant cultures. In our culture condition, TnTs formation occurred after large membrane adhesion. We showed that intercellular transfers of cytoplasmic content occurred similarly between cancer cells and MSCs or ECs, but we highlighted that the exchange of mitochondria occurred preferentially between endothelial cells and cancer cells. We illustrated that the cancer cells acquiring mitochondria displayed chemoresistance. Our results illustrate the perfusion-independent role of the endothelium by showing a direct endothelial to cancer cell mitochondrial exchange associated to phenotypic modulation. This supports another role of the endothelium in the constitution of the metastatic niche. Citation Format: Jennifer Pasquier, Bella s. Guerrouahen, Hamda Al. Thawadi, Nadine Abu Kaoud, Mahtab Maleki, Frank Le Foll, Arash Rafii. Preferential transfer of mitochondria from endothelial to cancer cells through tunneling nanotubes modulates chemoresistance. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: From Concept to Clinic; Sep 18-21, 2013; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2013;19(19 Suppl):Abstract nr B69.

Cyclin D1 affects epithelial–mesenchymal transition in epithelial ovarian cancer stem cell-like cells

BackgroundThe association of cancer stem cells with epithelial–mesenchymal transition (EMT) is receiving attention. We found in our previous study that EMT existed from CD24− phenotype cells to their differentiated cells. It was shown that cyclin D1 functioned in sustaining self-renewal independent of CDK4/CDK6 activation, but its effect on the EMT mechanism in ovarian cancer stem cells is unclear.MethodsThe anchorage-independent spheroids from ovarian adenocarcinoma cell line 3AO were formed in a serum-free medium. CD24− and CD24+ cells were isolated by fluorescence-activated cell sorting. Cell morphology, viability, apoptosis, and migratory ability were observed. Stem-related molecule Bmi-1, Oct-4 and EMT-related marker E-cadherin, and vimentin expressions were analyzed. Cyclin D1 expression in CD24− phenotype enriched spheroids was knocked down with small interfering RNA, and its effects on cell proliferation, apoptosis, migration ability, and EMT-related phenotype after transfection were observed.ResultsIn our study, CD24− cells presented stronger proliferative, anti-apoptosis capacity, and migratory ability, than CD24+ cells or parental cells. CD24− cells grew with a scattered spindle-shape within 3 days of culture and transformed into a cobblestone-like shape, identical to CD24+ cells or parental cells at 7 days of culture. CD24− cells or spheroids highly expressed cyclin D1, Bmi-1, and vimentin, and seldom expressed E-cadherin, while CD24+ or parental cells showed the opposite expression. Furthermore, cyclin D1-targeted small interfering RNA resulted in decreased vimentin expression in spheroids. Transfected cells also exhibited an obvious decrease in cell viability and migration, but an increase in cell apoptosis.ConclusionCancer stem cell-like cells possess mesenchymal characteristics and EMT ability, and cyclin D1 involves in EMT mechanism, suggesting that EMT of cancer stem cell-like cells may play a key role in invasion and metastasis of ovarian cancer.

Abstract 1254: FAK activity regulates αvβ5 integrin and osteopontin expression to control breast and ovarian cancer anchorage-independent growth

Abstract Focal adhesion kinase (FAK) is a cytoplasmic tyrosine kinase that controls cell motility and survival downstream of integrin receptors. FAK expression and activity are elevated during breast and ovarian cancer progression and this is associated with a poor clinical prognosis. Small molecule FAK inhibitors (FAK-I) block breast and ovarian tumor progression through a novel mechanism that is associated with the apoptosis under anchorage-deprived conditions. Metastatic cells can grow as anchorage-independent spheroids and we hypothesize that a spheroid micro-environment remains dependent on integrin- and FAK-associated signaling for survival. Here we show that intraperitoneal (ip) injection of murine ID8 ovarian carcinoma cells into mice, recovery of ascites-associated tumor cells (ID8ip) and growth ex vivo, yielded tumor cells with elevated levels of phosphorylated FAK (Y397 and Y576 phosphorylation), αvβ5 integrin, and osteopontin (OPN) matrix protein expression compared to parental ID8 cells. Analyses of paraffin-embedded breast and ovarian tumor sections revealed significantly higher pY397 FAK (p<0.05), β5 integrin (p<0.0001), and OPN expression (p<0.005) in stage II-III compared to stage I tumors. Treatment of ovarian ID8ip, human ovarian HEY carcinoma, or human MDA-MB-231 breast carcinoma cells with FAK-I inhibited cell growth, prevented FAK Y397 phosphorylation, reduced β5 integrin and OPN levels independent of effects on β1 or β3 integrins or changes in matrix proteins such as fibronectin. FAK-I impairs anchorage independent cell growth and orthotopic tumor growth but not growth of cells in plastic-adherent cell culture. Stable knockdown of either FAK or β5 integrin in HEY cells prevented anchorage-independent growth. Re-expression of wildtype or kinase-dead FAK within HEY cells verified the importance of FAK activity in promoting β5 integrin and OPN expression associated with enhanced tumor growth. Ongoing studies are focused on determining the molecular connections of FAK to the regulation of αvβ5 and OPN expression. Together, our studies support a novel role for a signaling loop involving OPN and αvβ5 integrin leading to FAK activation and reinforcement of OPN and β5 integrin expression within the spheroid and tumor micro-environment enhancing breast and ovarian cancer cell survival and tumor progression. Supported by Susan G. Komen for the Cure (KG111237) and NIH grant CA102310 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 1254. doi:1538-7445.AM2012-1254

Repression of mammosphere formation of human breast cancer cells by soy isoflavone genistein and blueberry polyphenolic acids suggests diet-mediated targeting of cancer stem-like/progenitor cells

Mammary stem cells are undifferentiated epithelial cells, which initiate mammary tumors and render them resistant to anticancer therapies, when deregulated. Diets rich in fruits and vegetables are implicated in breast cancer risk reduction, yet underlying mechanisms are poorly understood. Here, we addressed whether dietary factors selectively target mammary epithelial cells that display stem-like/progenitor subpopulations with previously recognized tumor-initiating potential. Using estrogen receptor-positive MCF-7 and estrogen receptor-negative MDA-MB-231 human breast cancer cell lines and freshly isolated epithelial cells from MMTV-Wnt-1 transgenic mouse mammary tumors, we demonstrate that sera of adult mice consuming soy isoflavone genistein (GEN) or blueberry (BB) polyphenol-containing diets alter the population of stem-like/progenitor cells, as measured by their functional ability to self-renew and form anchorage-independent spheroid cultures in vitro at low frequency (1-2%). Serum effects on mammosphere formation were dose-dependently replicated by GEN (40 nM >2 μM) and targeted the basal stem-like CD44+/CD24-/ESA+ and the luminal progenitor CD24+ subpopulations in MDA-MB-231 and MCF-7 cells. GEN inhibition of mammosphere formation was mimicked by the Akt inhibitor perifosine and was associated with enhanced tumor suppressor phosphatase and tensin homologue deleted on chromosome ten (PTEN) expression. In contrast, a selected mixture of BB phenolic acids was only active in MDA-MD-231 cells and its CD44+/CD24-/ESA+ subpopulation, and this activity was independent of induction of PTEN expression. These findings delineate a novel and selective function of distinct dietary factors in targeting stem/progenitor cell populations in estrogen receptor-dependent and -independent breast cancers.

Anchorage dependency effects on difluoromethylornithine cytotoxicity in human lung carcinoma cells

Difluoromethylornithine (DFMO), a specific, irreversible, enzyme-activated inhibitor of ornithine decarboxylase activity, the first and rate-limiting step in polyamine biosynthesis, has been shown to inhibit neoplastic cell proliferation in culture. In most cases, such inhibition is not accompanied by cell loss, with the exception of multiple cell lines of human small cell lung carcinoma (SCC), a human leukemia cell line (HL-60), and possibly the B16 melanoma cell line. The first two cell types grow as anchorage-independent suspension cultures, the HL-60 as single cells and the SCC as multicellular spheroid aggregates. Moreover, in the spectrum of human lung carcinoma cells in culture, the SCC cells respond in a cytotoxic manner to DFMO, whereas the non-small cell lung carcinoma (non-SCC) cells, which are anchorage dependent, show only growth inhibition, without actual cell loss. In the present study, we have investigated relationships between anchorage-dependent and -independent growth patterns of cells in culture and their response to DFMO treatment. Two non-SCC lung cancer cell lines, which normally grow as anchorage-dependent monolayers, show growth inhibition but no cell loss with the addition of DFMO. When these anchorage-dependent cells were forced to grow as multicellular aggregates, by coating the culture flask with Teflon, the cells developed an increased sensitivity to DFMO. They showed not only inhibition of cell proliferation but also cell death. Two SCC cell lines, which normally grow as anchorage-independent spheroids, developed adherence to the culture dishes coated with fibronectin. These cells, which show a cytotoxic response to DFMO during normal anchorage-independent growth, developed a decreased sensitivity to DFMO, showing only cell growth inhibition, but no cell death when treated during anchorage-dependent growth. Our data thus suggest that the state of anchorage dependence of lung cancer cells in culture is a critical factor in determining their response to polyamine depletion during treatment with DFMO.