Suppression of the antitumoral activity of natural killer cells under indirect coculture with cancer-associated fibroblasts in a pancreatic TIME-on-chip model

BACKGROUND

Recently, natural killer (NK) cells emerged as a treatment option for various solid tumors. However, the immunosuppressive tumor immune microenvironment (TIME) can reduce the cytotoxic ability of NK cells in pancreatic ductal adenocarcinoma. Cancer-associated fibroblasts within the tumor stroma can suppress immune surveillance by dysregulating factors involved in the cellular activity of NK cells. Herein, the effect of activated pancreatic stellate cells (aPSCs) on NK cell-mediated anticancer efficacy under three-dimensional (3D) coculture conditions was investigated.

METHODS

3D cocultures of PANC-1 tumor spheroids (TSs) with aPSCs and NK-92 cells in a collagen matrix were optimized to identify the occurring cellular interactions and differential cytokine profiles in conditioned media using microchannel chips. PANC-1 TSs and aPSCs were indirectly cocultured, whereas NK-92 cells were allowed to infiltrate the TS channel using convective medium flow.

RESULTS

Coculture with aPSCs promoted PANC-1 TSs growth and suppressed the antitumor cytotoxic effects of NK-92 cells. Mutual inhibition of cellular activity without compromising migration ability was observed between aPSCs and NK-92 cells. Moreover, the reduced killing activity of NK-92 cells was found to be related with reduced granzyme B expression in NK cells.

CONCLUSIONS

Herein, a novel TIME-on-chip model based on the coculture of PANC-1 TSs, aPSCs, and NK-92 cells was described. This model may be useful for studying the detailed mechanisms underlying NK cells dysregulation and for exploring future therapeutic interventions to restore NK cell activity in the tumor microenvironment.

Effect of paclitaxel priming on doxorubicin penetration in a multicellular layer model of human colorectal cancer cells

Tumor priming is considered a promising strategy for improving drug distribution in malignant tissues. Multicellular layers (MCLs) of human cancer cells are potentially useful models for evaluating tumor-priming agents. We evaluated the priming effects of paclitaxel (PTX) on doxorubicin (DOX) penetration using MCLs of the human colorectal cancer cell lines including DLD-1, HCT-116, and HT-29. The penetration of DOX treated at 50 μM for 3 h was highly limited in all three MCLs. The penetration of the priming agent PTX into MCLs was determined using rhodamine-labeled PTX and appeared to be cell line-dependent: full penetration was observed in HCT-116 and HT-29 MCLs, whereas only limited penetration occurred in DLD-1 MCLs. PTX pretreatment at 20 μM for 24 or 48 h induced a tumor-priming effect in DOX distribution, with a 3 to 5.6-fold-increase in HCT-116 and HT-29 MCLs but a less than two-fold increase in DLD-1 MCLs. PTX treatment decreased fibronectin expression in HCT-116 and HT-29 MCLs but not in DLD-1, suggesting that the prominent priming effect of PTX in HCT-116 and HT-29 MCLs may be associated with the downregulation of fibronectin expression. Our study demonstrated that MCLs of human cancer cells are a useful model not only for the study of drug penetration into tumor tissues but also for screening and evaluating tumor-priming agents.

Anti-Cancer Activity Profiling of Chemotherapeutic Agents in 3D Co-Cultures of Pancreatic Tumor Spheroids with Cancer-Associated Fibroblasts and Macrophages

Activated pancreatic stellate cells (aPSCs) and M2 macrophages modulate tumor progression and therapeutic efficacy in pancreatic ductal adenocarcinoma (PDAC) via epithelial-mesenchymal transition (EMT). Here, our aim was to analyze the anti-invasion effects of anti-cancer agents where EMT-inducing cancer-stroma interaction occurs under three-dimensional (3D) culture conditions. We used microfluidic channel chips to co-culture pancreatic tumor spheroids (TSs) with aPSCs and THP-1-derived M2 macrophages (M2 THP-1 cells) embedded in type I collagen. Under stromal cell co-culture conditions, PANC-1 TSs displayed elevated expression of EMT-related proteins and increased invasion and migration. When PANC-1 TSs were exposed to gemcitabine, 5-fluorouracil, oxaliplatin, or paclitaxel, 30-50% cells were found unaffected, with no significant changes in the dose-response profiles under stromal cell co-culture conditions. This indicated intrinsic resistance to these drugs and no further induction of drug resistance by stromal cells. Paclitaxel had a significant anti-invasion effect; in contrast, oxaliplatin did not show such effect despite its specific cytotoxicity in M2 THP-1 cells. Overall, our findings demonstrate that the TS-stroma co-culture model of PDAC is useful for activity profiling of anti-cancer agents against cancer and stromal cells, and analyzing the relationship between anti-stromal activity and anti-invasion effects.

Depletion of ST6GALNACIII retards A549 non-small cell lung cancer cell proliferation by downregulating transferrin receptor protein 1 expression

Alterations in sialylation of terminal residues of glycoproteins have been implicated in forming tumor-associated glycans. ST6GALNAC transfers sialyl moiety to N-acetylgalactosamine residue via α2,6 linkage. Although the oncogenic characteristics of ST6GALNACI or II have been demonstrated in various cancer cells, the impact of ST6GALNACIII on tumor progression remains undefined. In this study, we evaluated the effect of ST6GALNACIII knockdown on the growth of A549 non-small cell lung cancer cells. ST6GALNACIII depletion resulted in significant retardation in growth of A549 cells under various culture conditions, including collagen-supported 3D culture and anchorage-independent soft agar culture conditions. Liquid chromatography with tandem mass spectrometry revealed that two glycopeptides of transferrin receptor protein 1 (TFR1) containing N-acetylhexosamine-sialic acid were not detected in ST6GALNACIII-depleted A549 cells compared with control cells. Subsequent lectin binding assay, western blotting, and real-time RT-PCR indicated that TFR1 sialylation was not significantly changed, but TFR1 protein and mRNA expressions were decreased after ST6GALNACIII knockdown. However, cell growth retardation by ST6GALNACIII knockdown was partially rescued by TFR1 overexpression. Additionally, TFR1 mRNA degradation was accelerated following ST6GALNACIII knockdown with concomitant reduction in mRNA levels of iron regulatory protein 1 and 2, the upstream regulators of TFR1 mRNA stability. Therefore, our results indicated an important role of ST6GALNACIII in promoting A549 cell growth through quantitative regulation of TFR1 expression and provided therapeutic implications for ST6GALNACIII targeting in tumor growth suppression in vivo.

Three-Dimensional Imaging for Multiplex Phenotypic Analysis of Pancreatic Microtumors Grown on a Minipillar Array Chip

Three-dimensional (3D) culture of tumor spheroids (TSs) within the extracellular matrix (ECM) represents a microtumor model that recapitulates human solid tumors in vivo, and is useful for 3D multiplex phenotypic analysis. However, the low efficiency of 3D culture and limited 3D visualization of microtumor specimens impose technical hurdles for the evaluation of TS-based phenotypic analysis. Here, we report a 3D microtumor culture-to-3D visualization system using a minipillar array chip combined with a tissue optical clearing (TOC) method for high-content phenotypic analysis of microtumors. To prove the utility of this method, phenotypic changes in TSs of human pancreatic cancer cells were determined by co-culture with cancer-associated fibroblasts and M2-type tumor-associated macrophages. Significant improvement was achieved in immunostaining and optical transmission in each TS as well as the entire microtumor specimen, enabling optimization in image-based analysis of the morphology, structural organization, and protein expression in cancer cells and the ECM. Changes in the invasive phenotype, including cellular morphology and expression of epithelial-mesenchymal transition-related proteins and drug-induced apoptosis under stromal cell co-culture were also successfully analyzed. Overall, our study demonstrates that a minipillar array chip combined with TOC offers a novel system for 3D culture-to-3D visualization of microtumors to facilitate high-content phenotypic analysis.

Phenotypic Heterogeneity and Plasticity of Cancer Cell Migration in a Pancreatic Tumor Three-Dimensional Culture Model

Invasive cancer cell migration is a key feature of metastatic human pancreatic ductal adenocarcinoma (PDAC), yet the underlying mechanisms remain poorly understood. Here, we investigated modes of cancer cell invasion using two pancreatic cancer cell lines with differential epithelial–mesenchymal status, PANC-1 and BxPC-3, under 3D culture conditions. Multicellular tumor spheroids (TSs) were grown in a collagen matrix co-cultured with pancreatic stellate cells (PSCs) using microchannel chips. PANC-1 cells showed individual migration from TSs via invadopodium formation. BxPC-3 cells showed plasticity between collective and individual migration in either mesenchymal mode, with filopodium-like protrusions, or blebby amoeboid mode. These two cell lines showed significantly different patterns of extracellular matrix (ECM) remodeling, with MMP-dependent degradation in a limited area of ECM around invadopodia for PANC-1 cells, or MMP-independent extensive deformation of ECM for BxPC-3 cells. Cancer cell migration out of the collagen channel significantly increased by PSCs and directional cancer cell migration was mediated by fibronectin deposited by PSCs. Our results highlight the phenotypic heterogeneity and plasticity of PDAC cell migration and ECM remodeling under 3D culture conditions. This 3D co-culture model of pancreatic cancer cells and PSCs offers a useful tool for studying cancer cell migration and ECM remodeling to identify and develop potential molecular targets and anti-cancer agents against human PDAC.

Downregulation of BIS sensitizes A549 cells for digoxin-mediated inhibition of invasion and migration by the STAT3-dependent pathway

Digoxin, a compound of the cardiac glycoside family, was originally prescribed for heart failure but has recently been rediscovered for its potent antitumor activity. However, it has a narrow therapeutic margin due to its cardiotoxicity, limiting its safe use as an antitumor agent in clinical practice. To widen its therapeutic margin, we investigated whether the antitumor effect of digoxin is potentiated by the depletion of BCL-2-interacting cell death suppressor (BIS) in A549 lung cancer cells. BIS is a multifunctional protein that is frequently overexpressed in most human cancers including lung cancer. Our results demonstrated that the inhibitory potential of digoxin on the migratory behavior of A549 cells is significantly enhanced by BIS depletion as assessed by transwell assay and collagen-incorporated 3D spheroid culture. Western blotting revealed that combination treatment significantly reduces p-STAT3 expression. In addition, a STAT3 inhibitor substantially suppressed the aggressive phenotypes of A549 cells. Thus, our results suggest that loss of STAT3 activity is a possible molecular mechanism for the synergistic effect of digoxin and BIS depletion. Our findings suggest the sensitizing role of BIS silencing to reduce the dose of digoxin for treatment of lung cancer with a high metastatic potential.

Abstract B086: Cellular context-dependent regulation of cancer cell invasion and migration in pancreatic tumor spheroids co-cultured with pancreatic stellate cells

Purpose Invasion of cancer cells is the initial step of metastatic progression. Elucidation of the cellular and molecular mechanisms of invasion may provide novel strategies to modulate metastasis and survival. The plasticity of cancer cells and surrounding stroma induces cell migration of which three types have been reported: collective, mesenchymal, or amoeboid type of movement. Here we investigated differential invasion phenotype and underlying mechanisms using two pancreatic cancer cells, BxPC-3 (wild-type KRAS, epithelial type) and PANC-1 (mutated KRAS, intermediate type) under 3D culture conditions. Methods Multicellular tumor spheroids (TS) were cultured in 3D collagen gel matrix either as mono-culture or under pancreatic stellate cell (PSC) co-culture condition using micro-channel chips. TS formation, cell migration within and outside of collagen gel, ECM remodeling, and expression of proteins involved in epithelial-mesenchymal transition (EMT) as well as degradation of matrix proteins were evaluated using immunofluorescence confocal microscopy, real-time live cell imaging and subsequent image analysis. Results BxPC-3 cells formed highly compact TS with strong expression of E-cadherin compared to PANC-1 cells. BxPC-3 cells showed collective migration under mono-culture condition and showed 50% phenotypic conversion to amoeboid single cell migration under PSC co-culture condition. Lamellipodia formation with actin spikes were observed in both types of cell migration in BxPC-3 cells. PANC-1 cells showed mostly mesenchymal invasion with single cells migrating out of TS using invadopodia. PANC-1 cells showed significantly higher level of vimentin and TGF-β as compared to BxPC-3 cells. Extensive ECM remodeling with collagen densification and fiber alignment was shown with BxPC-3 cells, compared to that of PANC-1 cells, under both mono- and PSC co-culture conditions. Similar levels of collagen degradation and expression of MT1-MMP, integrin β1 and pFAK between the two cell lines strongly suggest additional mechanisms of mechanical deformation of ECM facilitated by traction force of BxPC-3 cells, which warrants further studies. When cancer cells and PSCs migrated out of collagen matrix channels to encounter, fibronectin-mediated cell-cell interaction leading to co-migration was observed in both cell lines. Conclusions We demonstrated cellular context-dependent regulation of cancer cell invasion and its association with cancer cell-ECM and cancer cell-PSC interaction in pancreatic TS co-cultured with PSC. Our 3D TS-PSC co-culture recapitulates the differential modes of cancer cell invasion; hence, it may serve as an efficient and in vivo mimic model to study cellular and molecular mechanisms of invasion.

Citation Format: Seul-ki Kim, Min-Suk Oh, Hyo-Jeong Kuh. Cellular context-dependent regulation of cancer cell invasion and migration in pancreatic tumor spheroids co-cultured with pancreatic stellate cells [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr B086. doi:10.1158/1535-7163.TARG-19-B086

Multiplex quantitative analysis of stroma-mediated cancer cell invasion, matrix remodeling, and drug response in a 3D co-culture model of pancreatic tumor spheroids and stellate cells

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a stroma-rich carcinoma, and pancreatic stellate cells (PSCs) are a major component of this dense stroma. PSCs play significant roles in metastatic progression and chemoresistance through cross-talk with cancer cells. Preclinical in vitro tumor model of invasive phenotype should incorporate three-dimensional (3D) culture of cancer cells and PSCs in extracellular matrix (ECM) for clinical relevance and predictability.

METHODS

PANC-1 cells were cultured as tumor spheroids (TSs) using our previously developed minipillar chips, and co-cultured with PSCs, both embedded in collagen gels. Effects of PSC co-culture on ECM fiber network, invasive migration of cancer cells, and expression of epithelial-mesenchymal transition (EMT)-related proteins were examined. Conditioned media was also analyzed for secreted factors involved in cancer cell-PSC interactions. Inhibitory effect on cancer cell invasion was compared between gemcitabine and paclitaxel at an equitoxic concentration in PANC-1 TSs co-cultured with PSCs.

RESULTS

Co-culture condition was optimized for the growth of TSs, activation of PSCs, and their interaction. Increase in cancer cell invasion via ECM remodeling, invadopodia formation and EMT, as well as drug resistance was recapitulated in the TS-PSC co-culture, and appeared to be mediated by cancer cell-PSC interaction via multiple secreted factors, including IL-6, IL-8, IGF-1, EGF, TIMP-1, uPA, PAI-1, and TSP-1. Compared to gemcitabine, paclitaxel showed a greater anti-invasive activity, which was attributed to suppresion of invadopodia formation in cancer cells as well as to PSC-specific cytotoxicity abrogating its paracrine signaling.

CONCLUSIONS

Here, we established 3D co-culture of TSs of PANC-1 cells and PSCs using minipillar histochips as a novel tumoroid model of PDAC. Our results indicate usefulness of the present co-culture model and multiplex quantitative analysis method not only in studying the role of PSCs and their interactions with tumor cell towards metastatic progression, but also in the drug evaluation of stroma-targeting drugs.

Combinatorial Antitumor Activity of Oxaliplatin with Epigenetic Modifying Agents, 5-Aza-CdR and FK228, in Human Gastric Cancer Cells

Epigenetic silencing is considered to be a major mechanism for loss of activity in tumor suppressors. Reversal of epigenetic silencing by using inhibitors of DNA methyltransferase (DNMT) or histone deacetylases (HDACs) such as 5-Aza-CdR and FK228 has shown to enhance cytotoxic activities of several anticancer agents. This study aims to assess the combinatorial effects of gene-silencing reversal agents (5-Aza-CdR and FK228) and oxaliplatin in gastric cancer cells, i.e., Epstein-Barr virus (EBV)-negative SNU-638 and EBV-positive SNU-719 cells. The doublet combinatorial treatment of 5-Aza-CdR and FK228 exhibited synergistic effects in both cell lines, and this was further corroborated by Zta expression induction in SNU-719 cells. Three drug combinations as 5-Aza-CdR/FK228 followed by oxaliplatin, however, resulted in antagonistic effects in both cell lines. Simultaneous treatment with FK228 and oxaliplatin induced synergistic and additive effects in SNU-638 and SNU-719 cells, respectively. Three drug combinations as 5-Aza-CdR prior to FK228/oxaliplatin, however, again resulted in antagonistic effects in both cell lines. This work demonstrated that efficacy of doublet synergistic combination using DNMT or HDACs inhibitors can be compromised by adding the third drug in pre- or post-treatment approach in gastric cancer cells. This implies that the development of clinical trial protocols for triplet combinations using gene-silencing reversal agents should be carefully evaluated in light of their potential antagonistic effects.

Implication of BIS in the Migration and Invasion of A549 Non-small Cell Lung Cancer Cells

BACKGROUND/AIM

High expression of the Bcl-2-interacting cell death suppressor (BIS), an anti-apoptotic protein, in various human cancers is linked to a poor outcome. The purpose of this study was to clarify whether BIS is associated with the migration and invasive characteristics of A549 cells.

MATERIALS AND METHODS

BIS-knockout (KO) cells were prepared by the CRISPR/Cas9 method. The aggressive behaviors of A549 cells were analyzed by wound healing and a transwell invasion assay as well as 3D spheroid culture.

RESULTS

BIS depletion resulted in significant inhibition of the migration and invasive potential of A549 cells which was accompanied by an increased ratio of E-cadherin/N-cadherin and a decrease in the mRNA levels of Zeb1, Snail, Slug and MMP-2. NF-ĸB activity was suppressed in BIS-KO A549 cells due to the decrease in p65 protein levels, but not in mRNA levels.

CONCLUSION

BIS regulates cell invasion and the induction of the epithelial-mesenchymal transition (EMT) phenotype in A549 cells probably via the NF-ĸB signaling pathway.

Implication of BIS in the Migration and Invasion of A549 Non-small Cell Lung Cancer Cells

BACKGROUND/AIM

High expression of the Bcl-2-interacting cell death suppressor (BIS), an anti-apoptotic protein, in various human cancers is linked to a poor outcome. The purpose of this study was to clarify whether BIS is associated with the migration and invasive characteristics of A549 cells.

MATERIALS AND METHODS

BIS-knockout (KO) cells were prepared by the CRISPR/Cas9 method. The aggressive behaviors of A549 cells were analyzed by wound healing and a transwell invasion assay as well as 3D spheroid culture.

RESULTS

BIS depletion resulted in significant inhibition of the migration and invasive potential of A549 cells which was accompanied by an increased ratio of E-cadherin/N-cadherin and a decrease in the mRNA levels of Zeb1, Snail, Slug and MMP-2. NF-κB activity was suppressed in BIS-KO A549 cells due to the decrease in p65 protein levels, but not in mRNA levels.

CONCLUSION

BIS regulates cell invasion and the induction of the epithelial-mesenchymal transition (EMT) phenotype in A549 cells probably via the NF-κB signaling pathway.

Three Dimensional Mixed-Cell Spheroids Mimic Stroma-Mediated Chemoresistance and Invasive Migration in hepatocellular carcinoma

Interactions between cancer cells and cancer-associated fibroblasts (CAFs) within the tumor microenvironment (TME) play an important role in promoting the profibrotic microenvironment and epithelial-mesenchymal transition (EMT), resulting in tumor progression and drug resistance in hepatocellular carcinoma (HCC). In the present study, we developed a mixed-cell spheroid model using Huh-7 HCC cells and LX-2 stellate cells to simulate the in vivo tumor environment with respect to tumor-CAF interactions. Spheroids were cultured from cancer cells alone (monospheroids) or as a mixture (mixed-cell spheroids) in ultra-low-attachment plates. Compact, well-mixed, and stroma-rich mixed-cell spheroids were successfully established with heterotypic cell-cell contacts shown by the presence of gap junctions and desmosomes. Mixed-cell spheroids showed enhanced expression of collagen type-I (Col‐I) and pro‐fibrotic factors such as, transforming growth factor beta1 (TGF-β1), and connective tissue growth factor (CTGF) compared to the levels expressed in mono-spheroids. The EMT phenotype was evident in mixed-cell spheroids as shown by the altered expression of E-cadherin and vimentin. Differential drug sensitivity was observed in mixed-cell spheroids, and only sorafenib and oxaliplatin showed dose-dependent antiproliferative effects. Simultaneous treatment with TGF-β inhibitors further improved sorafenib efficacy in the mixed-cell spheroids, indicating the involvement of TGF-β in the mechanism of sorafenib resistance. In 3D matrix invasion assay, mixed-cell spheroids exhibited fibroblast-led collective cell movement. Overall, our results provide evidence that mixed-cell spheroids formed with Huh-7 and LX-2 cells well represent HCC tumors and their TME in vivo and hence are useful in studying tumor-stroma interactions as mechanisms associated with drug resistance and increased cell motility.

Abstract 2114: 3D co-culture of pancreatic tumor sphroids and stellate cells using minipillar array as a microtumor model of pancreatic ductal adenocarcinoma

Purpose: Tumor microenvironmental (TME) factors play important roles in cancer progression and chemoresistance by inducing epithelial-mesenchymal transition (EMT) and related mechanisms. Pancreatic stellate cell (PSC) is a highly-enriched cell type in TME of pancreatic ductal adenocarcinoma (PDAC). Three dimensional (3D) tumor spheroids (TS) are considered as an in vivo-like tumor model demonstrating its clinical relevancy. We previously developed a minipillar array histochip for 3D culture and immunohistological analysis of TS in an increased throughput manner. Here, we present a minipillar-based co-culture of TS and PSC as a novel in vitro microtumor model of pancreatic ductal adenocarcinoma. Methods: Minipillar chips were obtained from MBD Co. (Cellvitro™ 55Cryo). 3D TS of Panc-1, human PDAC cells and PSCs (Sciencell) were cultured on minipillars and at the bottom of 96 well plates, respectively, as embedded in type I collagen. Changes in expression of extracellular matrix (ECM) and EMT-related factors in TS were assessed by confocal microscopy following cyrosection preparation. Results: Co-culture condition was optimized for the growth of TS, activation of PSC, and their interaction. Expression of EMT markers such as TGF-β1 and vimentin increased in co-cultured TS than mono-cultured TS. ECM remodeling as indicated by increased matrix deposition (collagen I, fibronectin) and fiber organization was observed in TS co-cultured with PSC compared to mono-cultured TS. Upon drug exposure (gemcitabine and paclitaxel), survival advantage was prominent in TS co-cultured with activated PSC. Conclusions: We established 3D model of PDAC by co-culturing TS and PSC using minipillar histochips. EMT-related changes including ECM remodeling and drug resistance were recapitulated in the model. Overall our results indicate usefulness of the present model not only in studying the role of TME factors and their interactions towards tumor progression but also in the evaluation of therapeutic efficacy of drug candidates and combinations.

Citation Format: Hyun Ju Hwang, Min-Suk Oh, Seul-Ki Kim, Hyo-Jeong Kuh. 3D co-culture of pancreatic tumor sphroids and stellate cells using minipillar array as a microtumor model of pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2114.

Microfluidic co-culture of pancreatic tumor spheroids with stellate cells as a novel 3D model for investigation of stroma-mediated cell motility and drug resistance

BACKGROUND

Pancreatic stellate cells (PSCs), a major component of the tumor microenvironment in pancreatic cancer, play roles in cancer progression as well as drug resistance. Culturing various cells in microfluidic (microchannel) devices has proven to be a useful in studying cellular interactions and drug sensitivity. Here we present a microchannel plate-based co-culture model that integrates tumor spheroids with PSCs in a three-dimensional (3D) collagen matrix to mimic the tumor microenvironment in vivo by recapitulating epithelial-mesenchymal transition and chemoresistance.

METHODS

A 7-channel microchannel plate was prepared using poly-dimethylsiloxane (PDMS) via soft lithography. PANC-1, a human pancreatic cancer cell line, and PSCs, each within a designated channel of the microchannel plate, were cultured embedded in type I collagen. Expression of EMT-related markers and factors was analyzed using immunofluorescent staining or Proteome analysis. Changes in viability following exposure to gemcitabine and paclitaxel were measured using Live/Dead assay.

RESULTS

PANC-1 cells formed 3D tumor spheroids within 5 days and the number of spheroids increased when co-cultured with PSCs. Culture conditions were optimized for PANC-1 cells and PSCs, and their appropriate interaction was confirmed by reciprocal activation shown as increased cell motility. PSCs under co-culture showed an increased expression of α-SMA. Expression of EMT-related markers, such as vimentin and TGF-β, was higher in co-cultured PANC-1 spheroids compared to that in mono-cultured spheroids; as was the expression of many other EMT-related factors including TIMP1 and IL-8. Following gemcitabine exposure, no significant changes in survival were observed. When paclitaxel was combined with gemcitabine, a growth inhibitory advantage was prominent in tumor spheroids, which was accompanied by significant cytotoxicity in PSCs.

CONCLUSIONS

We demonstrated that cancer cells grown as tumor spheroids in a 3D collagen matrix and PSCs co-cultured in sub-millimeter proximity participate in mutual interactions that induce EMT and drug resistance in a microchannel plate. Microfluidic co-culture of pancreatic tumor spheroids with PSCs may serve as a useful model for studying EMT and drug resistance in a clinically relevant manner.

Pitch-tunable pillar arrays for high-throughput culture and immunohistological analysis of tumor spheroids

Tumor spheroids are multicellular, three-dimensional (3D) cell culture models closely mimicking the microenvironments of human tumors in vivo, thereby providing enhanced predictability, clinical relevancy of drug efficacy and the mechanism of action. Conventional confocal microscopic imaging remains inappropriate for immunohistological analysis due to current technical limits in immunostaining using antibodies and imaging cells grown in 3D multicellular contexts. Preparation of microsections of these spheroids represents a best alternative, yet their sub-millimeter size and fragility make it less practical for high-throughput screening. To address these problems, we developed a pitch-tunable 5 × 5 mini-pillar array chip for culturing and sectioning tumor spheroids in a high throughput manner. Tumor spheroids were 3D cultured in an alginate matrix using a twenty-five mini-pillar array which aligns to a 96-well. At least a few tens of spheroids per pillar were cultured and as many as 25 different treatment conditions per chip were evaluated, which indicated the high throughput manner of the 5 × 5 pillar array chip. The twenty-five mini-pillars were then rearranged to a transferring pitch so that spheroid-containing gel caps from all pillars can be embedded into a specimen block. Tissue array sections were then prepared and stained for immunohistological examination. The utility of this pitch-tunable pillar array was demonstrated by evaluating drug distribution and expression levels of several proteins following drug treatment in 3D tumor spheroids. Overall, our mini-pillar array provides a novel platform that can be useful for culturing tumor spheroids as well as for immunohistological analysis in a multiplexed and high throughput manner.

A pitch-tunable 5 × 5 mini-pillar array chip was developed for culturing and sectioning tumor spheroids (TSs) in a high throughput manner. TSs were cultured on the chip aligned to 96-well. TS array sections were prepared following pitch rearrangement.

Antifibrotic effects of pentoxifylline improve the efficacy of gemcitabine in human pancreatic tumor xenografts

We investigated the combinatorial effects of pentoxifylline (PTX) on the efficacy of gemcitabine (GEM) in a human pancreatic tumor xenograft model. PTX significantly improved the efficacy of GEM, as shown by a 50% reduction in tumor growth rate at 4 weeks of treatment compared with that in animals given GEM alone. The fluorescent drug doxorubicin (DOX) was used to test whether drug delivery was improved by PTX, contributing to the improved efficacy of GEM. PTX given for 2 weeks prior to giving DOX improved drug distribution by 1.8‐ to 2.2‐fold with no changes in vessel density, suggesting that improvement in drug delivery was not related to the vascular mechanism. Instead, collagen I content in tumor stroma was significantly reduced, as was the expression of alpha‐smooth muscle actin of cancer‐associated fibroblasts and connective tissue growth factor (CTGF) by PTX pretreatment. Overall, our data demonstrated that increased efficacy of GEM by PTX was associated with improved drug delivery to tumor tissue, which may be attributed to decreased expression of CTGF and subsequent reduction in the stromal collagen matrix in the pancreatic ductal adenocarcinoma tumor. These results support the usefulness of PTX in combination with chemotherapy for targeting drug delivery barriers associated with the stromal matrix, which should be further evaluated for clinical development.

Abstract 5789: Characterization of mixed-cell spheroid as an in vitro model of hepatocellular carcinoma for epithelial-to-mesenchymal transition and chemoresistance

Interaction between cancer cells and stromal components in the tumor microenvironment is well known for their significant roles in tumor progression and subsequent treatment failure. Hepatic stellate cells (HSCs), as a predominant cell type in the microenvironment of hepatocellular carcinoma (HCC), are involved in creating desmoplastic and chemoresistance-inducing microenvironment. HSCs secrete various paracrine factors that modify the HCC tumor microenvironment leading to tumor growth, drug resistance and metastasis via promoting epithelial-to-mesenchymal transition (EMT). Although several studies using 2D co-culture system have shown bidirectional cross-talk between cancer cells and HSCs, data obtained remain limited in their clinical relevance due to lack of in vivo tumor-like characteristics.

We developed a mixed-cell spheroid model which recapitulates direct 3D tumor-HSCs interactions in paracrine and contact-mediated manners. Huh-7, human HCC cells, were mixed co-cultured with LX-2 cells, immortalized human HSC at 1:3 ratio using liquid overlay technique in 96-well plates. Electron microscopy was used to examine subcellular structural changes. Cellular distribution within spheroids was observed by labeling LX-2 cells with fluorescent tracer. The expression of pro-fibrotic and EMT markers was detected by immunohistochemistry or immunofluorescence staining on paraffin embedded sections. Invasion ability was determined using migration assay into 3D matrigel matrix. Dose-response curve was obtained by using APH assay and Ki-67 detection.

Mixed co-culture of Huh-7 and LX-2 cells showed a spontaneous self-organization forming highly compact mixed-cell spheroids with well-defined contour. Heterotypic cell-to-cell contact increased as shown by gap junction and desmosomes in the mixed-cell spheroids. LX-2 cells were uniformly distributed within the spheroids. Expression of fibroblast-associated factors such as α-SMA, collagen I, TGF-β and CTGF showed similar patterns of distribution to that of LX-2 cells, but at an elevated level in the mixed-cell spheroids compared to that of cancer cell-alone spheroids. An increased expression of EMT-related factors was observed along with enhanced invasion into 3D matrix. Differential drug sensitivity was shown; mixed-cell spheroids were sensitive to sorafenib but not to other agents including oxaliplatin, gemcitabine, and 5-FU. Based on these results, the mixed cell-spheroids of HCC cells-HSCs may be proposed as a useful 3D model for in vitro therapeutic screening of targets and agents as well as for the study of malignant progression in HCC.

Citation Format: Hyo-Jeong Kuh, Iftikhar Ali Khawar. Characterization of mixed-cell spheroid as an in vitro model of hepatocellular carcinoma for epithelial-to-mesenchymal transition and chemoresistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5789. doi:10.1158/1538-7445.AM2017-5789

Co-Culture of Tumor Spheroids and Fibroblasts in a Collagen Matrix-Incorporated Microfluidic Chip Mimics Reciprocal Activation in Solid Tumor Microenvironment

Multicellular 3D culture and interaction with stromal components are considered essential elements in establishing a ‘more clinically relevant’ tumor model. Matrix-embedded 3D cultures using a microfluidic chip platform can recapitulate the microscale interaction within tumor microenvironments. As a major component of tumor microenvironment, cancer-associated fibroblasts (CAFs) play a role in cancer progression and drug resistance. Here, we present a microfluidic chip-based tumor tissue culture model that integrates 3D tumor spheroids (TSs) with CAF in proximity within a hydrogel scaffold. HT-29 human colorectal carcinoma cells grew into 3D TSs and the growth was stimulated when co-cultured with fibroblasts as shown by 1.5-folds increase of % changes in diameter over 5 days. TS cultured for 6 days showed a reduced expression of Ki-67 along with increased expression of fibronectin when co-cultured with fibroblasts compared to mono-cultured TSs. Fibroblasts were activated under co-culture conditions, as demonstrated by increases in α-SMA expression and migratory activity. When exposed to paclitaxel, a survival advantage was observed in TSs co-cultured with activated fibroblasts. Overall, we demonstrated the reciprocal interaction between TSs and fibroblasts in our 7-channel microfluidic chip. The co-culture of 3D TS-CAF in a collagen matrix-incorporated microfluidic chip may be useful to study the tumor microenvironment and for evaluation of drug screening and evaluation.

Mini-pillar array for hydrogel-supported 3D culture and high-content histologic analysis of human tumor spheroids

Three-dimensional (3D) cancer cell culture models mimic the complex 3D organization and microenvironment of human solid tumor tissue and are thus considered as highly predictive models representing avascular tumor regions. Confocal laser scanning microscopy is useful for monitoring drug penetration and therapeutic responses in 3D tumor models; however, photonic attenuation at increasing imaging depths and limited penetration of common fluorescence tracers are significant technical challenges to imaging. Immunohistological staining would be a good alternative, but the preparation of tissue sections from rather fragile spheroids through fixing and embedding procedures is challenging. Here we introduce a novel 3 × 3 mini-pillar array chip that can be utilized for 3D cell culturing and sectioning for high-content histologic analysis. The mini-pillar array chip facilitated the generation of 3D spheroids of human cancer cells within hydrogels such as alginate, collagen, and Matrigel. As expected, visualization of the 3D distribution of calcein AM and doxorubicin by optical sectioning was limited by photonic attenuation and dye penetration. The integrity of the 3D microtissue section was confirmed by immunostaining on paraffin sections and cryo-sections. The applicability of the mini-pillar array for drug activity evaluation was tested by measuring viability changes in spheroids exposed to anti-cancer agents, 5-fluorouracil and tirapazamine. Thus, our novel mini-pillar array platform can potentially promote high-content histologic analysis of 3D cultures and can be further optimized for field-specific needs.

Co-culture of 3D tumor spheroids with fibroblasts as a model for epithelial-mesenchymal transition in vitro

Epithelial-mesenchymal transition (EMT) acts as a facilitator of metastatic dissemination in the invasive margin of malignant tumors where active tumor-stromal crosstalks take place. Co-cultures of cancer cells with cancer-associated fibroblasts (CAFs) are often used as in vitro models of EMT. We established a tumor-fibroblast proximity co-culture using HT-29 tumor spheroids (TSs) with CCD-18 co fibroblasts. When co-cultured with TSs, CCD-18 co appeared activated, and proliferative activity as well as cell migration increased. Expression of fibronectin increased whereas laminin and type I collagen decreased in TSs co-cultured with fibroblasts compared to TSs alone, closely resembling the margin of in vivo xenograft tissue. Active TGFβ1 in culture media significantly increased in TS co-cultures but not in 2D co-cultures of cancer cells-fibroblasts, indicating that 3D context-associated factors from TSs may be crucial to crosstalks between cancer cells and fibroblasts. We also observed in TSs co-cultured with fibroblasts increased expression of α-SMA, EGFR and CTGF; reduced expression of membranous β-catenin and E-cadherin, together suggesting an EMT-like changes similar to a marginal region of xenograft tissue in vivo. Overall, our in vitro TS-fibroblast proximity co-culture mimics the EMT-state of the invasive margin of in vivo tumors in early metastasis.

Improving drug delivery to solid tumors: priming the tumor microenvironment

Malignant transformation and growth of the tumor mass tend to induce changes in the surrounding microenvironment. Abnormality of the tumor microenvironment provides a driving force leading not only to tumor progression, including invasion and metastasis, but also to acquisition of drug resistance, including pharmacokinetic (drug delivery-related) and pharmacodynamic (sensitivity-related) resistance. Drug delivery systems exploiting the enhanced permeability and retention (EPR) effect and active targeting moieties were expected to be able to cope with delivery-related drug resistance. However, recent evidence supports a considerable barrier role of tumors via various mechanisms, which results in imperfect or inefficient EPR and/or targeting effect. The components of the tumor microenvironment such as abnormal tumor vascular system, deregulated composition of the extracellular matrix, and interstitial hypertension (elevated interstitial fluid pressure) collectively or cooperatively hinder the drug distribution, which is prerequisite to the efficacy of nanoparticles and small-molecule drugs used in cancer medicine. Hence, the abnormal tumor microenvironment has recently been suggested to be a promising target for the improvement of drug delivery to improve therapeutic efficacy. Strategies to modulate the abnormal tumor microenvironment, referred to here as "solid tumor priming" (vascular normalization and/or solid stress alleviation leading to improvement in blood perfusion and convective molecular movement), have shown promising results in the enhancement of drug delivery and anticancer efficacy. These strategies may provide a novel avenue for the development of new chemotherapeutics and combination chemotherapeutic regimens as well as reassessment of previously ineffective agents.

Indirect modulation of sensitivity to 5-fluorouracil by microRNA-96 in human colorectal cancer cells

5-FU is an anticancer drug that is widely used to treat cancers, including colorectal cancer (CRC); however, chemoresistance to 5-FU remains an important problem to be resolved. The role of microRNAs (miRs) in chemosensitivity has recently been studied in the development of therapeutic strategies to overcome drug resistance. Here, we focused on miR-96, which has been reported to demonstrate chemosensitivity. We investigated whether 5-FU sensitivity may be modulated by miR-96 in monolayer cells and whether this relationship also applies for drug resistance in 3D tumor spheroids (TSs). When the level of miR-96 increased, the expression of the anti-apoptotic regulator XIAP and p53 stability regulator UBE2N decreased, resulting in increased apoptosis and growth inhibition following 5-FU exposure. Transfection of miR-96 inhibitors resulted in an overexpression of XIAP and UBE2N, yet only minimal change was induced in apoptosis. Nonetheless, luciferase assay failed to show direct interactions between miR-96 and these genes. In TSs, 5-FU resistance corresponded to a significantly lower level of miR-96, however only XIAP, not UBE2N, was up-regulated demonstrating partial agreement with the 2D condition regarding target expression. Overall, these results suggest that miR-96 may modulate 5-FU sensitivity in CRC cells by promoting apoptosis; however, differential expression of target genes in TSs warrants further studies on the 5-FU resistance mechanism under 3D conditions.

Abstract 1970: Co-culture of 3D tumor spheroids with fibroblasts as an in vitro model for drug resistance study

Purpose. Chemotherapeutic failure of human solid tumor is attributed to tumor microenvironmental (TME) factors associated with drug resistance. Three dimensional (3D) tumor spheroid (TS) model is known to be in vivo mimic and has demonstrated its clinical relevancy. Fibroblasts in TME have been shown to play a significant role in drug resistance. The present study was to develop and characterize a co-culture of 3D TS with fibroblasts for human colorectal tumor model.

Methods. TS of human colorectal cancer cells (HT-29) was prepared by using liquid overlay method and co-cultured in collagen-coated 24-well plates with colon fibroblasts (CCD-18co) grown in Transwell® inserts. Differentail expression of extracellular matrix (ECM), growth signaling molecules, and microRNAs was analyzed using IHC, ELISA, western blot and qRT-PCR. For miRNA transfection study, changes in motility and drug sensitivity were measured by wound healing assays and APH or MTS assay, respectively.

Results. Significant resistance to 5-FU was shown in TS either with or without fibroblasts compared to monolayers. Compared to single culture of TS, co-culture with fibroblast showed 1.3-fold increased outgrowth on collagen gel, indicating increased motility. Cell-to-cell adhesion structures, expression of ECM and active form TGFβ1 were higher in TS-fibroblast co-culture. Expression of several growth- and TME-related factors, such as fibronectin, EGFR, β-catenin and CTGF, was higher in fibroblast co-culture up to the level of HT-29 xenograft tissues. Among miRNAs showing differential expressions, miR-96 showed down-regulation in TS. HT-29 cells transfected with miR-96 showed increase in cell motility, proliferation, and sensitivity to 5-FU, suggesting its potential role in regulation of genes associated with 5-FU resistance.

Conclusions. Co-culture of 3D TS-fibroblasts was successfully established and demonstrated in vivo mimic characteristics with respect to presence of adhesion microstructures, expression of ECM and growth signaling molecules, and resistance to 5-FU. MiR-96 showed its potential role in 3D drug resistance which warrants further studies.

Citation Format: Sun-Ah Kim, Hyo-Jeong Kuh. Co-culture of 3D tumor spheroids with fibroblasts as an in vitro model for drug resistance study. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1970. doi:10.1158/1538-7445.AM2014-1970

A long non-coding RNA snaR contributes to 5-fluorouracil resistance in human colon cancer cells

Several types of genetic and epigenetic regulation have been implicated in the development of drug resistance, one significant challenge for cancer therapy. Although changes in the expression of non-coding RNA are also responsible for drug resistance, the specific identities and roles of them remain to be elucidated. Long non-coding RNAs (lncRNAs) are a type of ncRNA (> 200 nt) that influence the regulation of gene expression in various ways. In this study, we aimed to identify differentially expressed lncRNAs in 5-fluorouracil-resistant colon cancer cells. Using two pairs of 5-FU-resistant cells derived from the human colon cancer cell lines SNU-C4 and SNU-C5, we analyzed the expression of 90 lncRNAs by qPCR-based profiling and found that 19 and 23 lncRNAs were differentially expressed in SNU-C4R and SNU-C5R cells, respectively. We confirmed that snaR and BACE1AS were downregulated in resistant cells. To further investigate the effects of snaR on cell growth, cell viability and cell cycle were analyzed after transfection of siRNAs targeting snaR. Down-regulation of snaR decreased cell death after 5-FU treatment, which indicates that snaR loss decreases in vitro sensitivity to 5-FU. Our results provide an important insight into the involvement of lncRNAs in 5-FU resistance in colon cancer cells.

Injectable poly(organophosphazene) hydrogel system for effective paclitaxel and doxorubicin combination therapy

Combination therapy is an important option for gastric cancer which is the second leading cause of cancer-related death worldwide. The administration schedule of cell cycle-specific drugs, such as doxorubicin (DOX) and paclitaxel (PTX), is important for therapeutic efficacy. However, to control the schedule is clinically inconvenient. Additionally, in vitro cytotoxicity tests against human gastric cancer cells (SNU-601) showed that the combination indices (CIs) of DOX and PTX were 1.43 (α=0) and 1.90 (α=1), respectively, indicating that the DOX and PTX interaction was antagonistic. Thus, based on the finding that the release rate of drugs from poly(organophosphazene) (PPZ) hydrogel is dependent on the hydrophobicity of the drugs, we used injectable PPZ hydrogel in combination therapy. In vivo anticancer activity test in human gastric cancer cell-xenografted mice showed that intratumoral injection with aqueous PPZ solution, containing DOX (15 mg/kg) and PTX (30 mg/kg), resulted in the highest tumor inhibition and safety (no mortality for approximately 3 months) in the experimental groups. Consequently, PPZ hydrogel is expected to be a promising drug delivery system for cell cycle-specific drugs, facilitating the control of their administration schedule for effective combination therapy.

Application of concave microwells to pancreatic tumor spheroids enabling anticancer drug evaluation in a clinically relevant drug resistance model

Intrinsic drug resistance of pancreatic ductal adenocarcinoma (PDAC) warrants studies using models that are more clinically relevant for identifying novel resistance mechanisms as well as for drug development. Tumor spheroids (TS) mimic in vivo tumor conditions associated with multicellular resistance and represent a promising model for efficient drug screening, however, pancreatic cancer cells often fail to form spheroids using conventional methods such as liquid overlay. This study describes the induction of TS of human pancreatic cancer cells (Panc-1, Aspc-1, Capan-2) in concave polydimethylsiloxane (PDMS) microwell plates and evaluation of their usefulness as an anticancer efficacy test model. All three cell lines showed TS formation with varying degree of necrosis inside TS. Among these, Panc-1 spheroid with spherical morphology, a rather rough surface, and unique adhesion structures were successfully produced with no notable necrosis in concave microwell plates. Panc-1 TS contained growth factors or enzymes such as TGF-β1, CTGF, and MT1-MMP, and extracellular matrix proteins such as collagen type I, fibronectin, and laminin. Panc-1 cells grown as TS showed changes in stem cell populations and in expression levels of miRNAs that may play roles in chemoresistance. Visualization of drug penetration and detection of viability indicators, such as Ki-67 and MitoSOX, were optimized for TS for quantitative analysis. Water-soluble tetrazolium (MTS) and acid phosphatase (APH) assays were also successfully optimized. Overall, we demonstrated that concave PDMS microwell plates are a novel platform for preparation of TS of weakly aggregating cells and that Panc-1 spheroids may represent a novel three-dimensional model for anti-pancreatic cancer drug screening.

Intratumoral delivery of paclitaxel using a thermosensitive hydrogel in human tumor xenografts

Poly(organophosphazene), a novel thermosensitive hydrogel, is an injectable drug delivery system (DDS) that transforms from sol to gel at body temperature. Paclitaxel (PTX) is a mitotic inhibitor used in the treatment of various solid tumors. Due to its poor solubility in water and efflux systems in the gastrointestinal tract, PTX is a good candidate for local DDS. Here, we evaluated the penetration kinetics of PTX released from the PTX-poly(organophosphazene) hydrogel mixture in multicellular layers (MCLs) of human cancer cells. We also investigated the tumor pharmacokinetics of PTX (60 mg/kg) when administered as an intratumoral injection using poly(organophosphazene) in mice with human tumor xenografts. When PTX was formulated at 0.6 % w/w into a 10 % w/w hydrogel, the in vitro and in vivo release were found to be 40 and 90 % of the dose, respectively, in a sustained manner over 4 weeks. Exposure of MCLs to PTX-hydrogel showed time-dependent drug penetration and accumulation. In mice, the hydrogel mass was well retained over 6 weeks, and the PTX concentration in the tumor tissue was maximal at 14 days, which rapidly decreased and coincided with rebound tumor growth after 14 days of suppression. These data indicate that PTX-hydrogel should be intratumorally injected every 14 days, or drug release duration should be prolonged in order to achieve a long-term antitumor effect. Overall, poly(organophosphazene) represents a novel thermosensitive DDS for intratumoral delivery of PTX, which can accommodate a large dose of the drug in addition to reducing its systemic exposure by restricting biodistribution to tumor tissue alone.

Abstract 2722: Characteristics of pancreatic cancer spheroids as a model for anticancer efficacy test

Compared to the conventional monolayers or suspension cultures, 3D culture models have drawn attention as a vivo-mimic model which can produce clinically relevant data. Among the several types of 3D culture models, multicellular spheroid (MCS) is a appropriate model for study of penetration and efficacy of anticancer agents. Purpose of this study was to establish MCS of human pancreatic cancer cell (Panc-1) and evaluate its usefulness as anticancer efficacy test. Panc-1 MCS was produced successfully by using poly-dimethylsiloxane(PDMS) microwell instead of agarose-coated 96-well system. MCS with average diameter of 375 μm was prepared in 700 μm microwells after 4 days of culture. Spherical morphology with rather rough surface and junctional structures in outer cell layers were observed with no notable necrotic area. Extracellular matrix proteins such as collagen I, fibronectin, and laminin were detected in the interstitial space of MCS. Stem cell population with CD44+/CD24+/ESA+ expression increased from 0.1% to 2.1% when cultured as MCS. miRNA expression profiling showed a difference between monolayers and MCS, i.e., 36 and 85 genes were up- and down-regulated in MCS, respectively. Imaging of drug penetration and viability indicators including MitoSOX, Edu incorporation, and Ki-67 expression were optimized for microwell format. Colorimetric assays of MTS and APH were performed after transferring MCS to 96-well plates. Overall, we demonstrated that PDMS microwell is an appropriate platform for preparation of MCS of Panc-1 cells and MCS showed different biological features from monolayers, suggesting that Panc-1 MCS prepared using PDMS microwell may be a useful 3D model for anticancer efficacy test.

Citation Format: Sang-Eun Yeon, Sang-Hoon Lee, Hyo-Jeong Kuh. Characteristics of pancreatic cancer spheroids as a model for anticancer efficacy test. [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 2722. doi:10.1158/1538-7445.AM2013-2722

Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.

Impact of Micellar Vehicles on in situ Intestinal Absorption Properties of Beta-Lapachone in Rats

The aim of the present study was to examine the effect of micellar systems on the absorption of beta-lapachone (b-lap) through different intestinal segments using a single-pass rat intestinal perfusion technique. B-lap was solubilized in mixed micelles composed of phosphatidylcholine and sodium deoxycholate, and in sodium lauryl sulfate (SLS)-based conventional micelles. Both mixed micelles and SLS micelles improved the in situ permeability of b-lap in all intestinal segments tested although the mixed micellar formulation was more effective in increasing the intestinal absorption of b-lap. The permeability of b-lap was greatest in the large intestinal segments. Compared with SLS micelles, the effective permeability coefficient values measured with mixed micelles were 5- to 23-fold higher depending on the intestinal segment. Our data suggest that b-lap should be delivered to the large intestine using a mixed micellar system for improved absorption.

Development of self-microemulsifying bilayer tablets for pH-independent fast release of candesartan cilexetil

The aim of this study was to design self-microemulsifying tablets for pH-independent fast release of poorly soluble candesartan cilexetil (CDC). To improve the solubility of CDC, a self-microemulsifying drug delivery system (SMEDDS) was prepared composed of Capryol 90, Tween 80 and tetraglycol at a ratio of 5:35:60. Drug containing SMEDDS was adsorbed onto Fujicalin and Neusilin UFL2, respectively, used as solidification carriers and subsequently compressed into tablets (self-microemulsifying tablet, SMET). SMET using Fujicalin exhibited immediate CDC release in pH 1.2 medium while Neusilin UFL2-based SMET showed fast release, especially at pH 6.5. Thus, optimized SMET could be produced with one layer of Fujicalin and the other layer with Neusilin UFL2, demonstrating CDC release of 75% of the initial dose within 15 min in all pH conditions (1.2, 4.5, and 6.5). The average diameter of emulsion droplets formed from SMET was less than 200 nm. It was thus expected that Fujicalin and Neusilin UFL2-based bi-layer SMET would overcome low oral bioavailability of CDC due to its limited solubility at physiological pH conditions in the gastrointestinal tract.

Development of estimation methods of skin oxidation and evaluation of anti-oxidative effects of genistein in topical formulations

The objective of the present study was to establish the method of measurement of hydrogen peroxide and to estimate the anti-oxidative effect of genistein in the skin. UVB induced skin oxidation and anti-oxidative effect of genistein formulations were evaluated by determining levels of hydrogen peroxide. The mechanism involved in the determination of hydrogen peroxide is based on a color reaction between ferric ion (Fe³⁺) and xylenol orange, often called FOX assay and subsequent monitoring of absorbance values of the reactant at 540 nm. The reaction was to some extent pH-dependent and detection sensitivity was greatest at pH 1.75. Genistein liposomal gel demonstrated better anti-oxidative effect with regard to lowering hydrogen peroxide levels elevated by UVB irradiation compared to genistein-suspended gel. A linear relationship has been observed between anti-oxidative effect of genistein and drug deposition in the skin tissue. Genistein liposomal gel resulting in the localization of the drug in the deeper skin led to improved anti-oxidative effect compared to genistein gel. The suggested method for evaluation of oxidation of the skin can be used as a tool to screen effective anti-oxidative agents and their delivery systems acting on the skin.

Abstract 5708: Interstitial protein delivery evaluated in multicellular layers model

The limited efficacy of protein drugs is related to their poor distribution in tumor tissue. We examined interstitial delivery of four model proteins of different molecular size and bioaffinity as formulated of non-formulated forms in multicellular layers (MCL) of human cancer cells. Model proteins were tumor necrosis factor-related apoptosis-including ligand (TRAIL), cetuximab, RNase A, and IgG. MCLs were cultured in Transwell inserts, exposed to drugs, then cryo-sectioned for image acquisition using fluorescence microscopy (fluorescent dye-labeled TRAIL, RNase A, IgG) or Immunohistochemistry (cetuximab). TRAIL and cetuximab showed partial penetration into MCLs, whereas RNase A and IgG showed little penetration. At 10-fold higher dose, a significant increase in penetration was observed for IgG only, while cetuximab showed an intense accumulation limited to the front layers. PEGylated TRAIL and a heparin-Pluronic nanogel formulation of RNase A showed significantly improved penetration that was attributed to increased stability and extracellular matrix binding, respectively. IgG penetration was significantly enhanced with PTX pretreatment as a penetration enhancer. MCL culture was successfully used for the evaluation of protein movement in the tumor interstitum. Four proteins showed limited interstitial penetration in MCL cultures. Bioaffinity, rather than molecular size, seems to have a positive effect on tissue penetration, although strong binding affinity may lead to sequestration in the front layers. Nanoformulations, such as PEGylation and heparin-Pluronic (HP) nanogel, or penetration enhancers are potential strategies to increase interstitial delivery of anticancer biologics.

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 5708. doi:1538-7445.AM2012-5708

Evaluation of interstitial protein delivery in multicellular layers model

The limited efficacy of anticancer protein drugs is related to their poor distribution in tumor tissue. We examined interstitial delivery of four model proteins of different molecular size and bioaffinity in multicellular layers (MCL) of human cancer cells. Model proteins were tumor necrosis factor-related apoptosis-including ligand (TRAIL), cetuximab, RNase A, and IgG. MCLs were cultured in Transwell inserts, exposed to drugs, then cryo-sectioned for image acquisition using fluorescence microscopy (fluorescent dye-labeled TRAIL, RNase A, IgG) or immunohistochemistry (cetuximab). TRAIL and cetuximab showed partial penetration into MCLs, whereas RNase A and IgG showed insignificant penetration. At 10-fold higher dose, a significant increase in penetration was observed for IgG only, while cetuximab showed an intense accumulation limited to the front layers. PEGylated TRAIL and RNase A formulated in a heparin-Pluronic (HP) nanogel showed significantly improved penetration attributable to increased stability and extracellular matrix binding, respectively. IgG penetration was significantly enhanced with paclitaxel pretreatment as a penetration enhancer. The present study suggests that MCL culture may be useful in evaluation of protein delivery in the tumor interstitium. Four model proteins showed limited interstitial penetration in MCL cultures. Bioaffinity, rather than molecular size, seems to have a positive effect on tissue penetration, although high binding affinity may lead to sequestration in the front cell layers. Polymer conjugation and nanoformulation, such as PEGylation and HP nanogel, or use of penetration enhancers are potential strategies to increase interstitial delivery of anticancer protein drugs.

The distribution and retention of paclitaxel and doxorubicin in multicellular layer cultures

Limited distribution of anticancer drugs has been recognized as a significant hurdle to efficacy. We investigated a detailed penetration/distribution profile of paclitaxel-rhodamine (PTX-rd) and doxorubicin (DOX) in multicellular layer (MCL) cultures of human cancer cells as an in vitro model for avascular regions of solid tumors. MCLs were exposed to drugs and fluorescent images of frozen sections were acquired for determination of drug penetration into MCL under various exposure conditions. PTX-rd and DOX showed drastically different profiles of penetration. DOX showed full penetration after 1 h and accumulation over 3 h, whereas PTX-rd showed slow and limited penetration, with accumulation only within the top 20% of layers by 2 h and insignificant penetration even at 72 h. Drug retention in MCL was more dependent on drug concentration, rather than exposure time, i.e., drug distribution increased by 6.3- and 2.5-fold for PTX-rd and DOX, respectively, when exposed to higher concentrations under comparable AUC exposure (1 μM × 24 h vs. 50 μM × 0.5 h). Anti-proliferative activity of PTX and DOX in MCL, as determined by cell cycle analysis, was minimal and may be attributed, at least in part, to their limited distribution in multicellular cultures. Overall, we demonstrated that penetration and retention of PTX and DOX in MCL was not only concentration- and time-dependent, but also schedule-dependent. It is suggested that slow releasing formulations or a slow infusion regimen may not necessarily be desirable, especially for PTX, due to insufficient penetration and accumulation which may result from a low local concentration at the target site.

The reciprocal interaction: chemotherapy and tumor microenvironment

Despite significant improvements in ways to treat cancer, numerous patients still die from this disease. One of the reasons for this inability to cure cancer is the lack of ability of drugs to penetrate target cells properly. While studies on drug resistance have focused on the molecular mechanisms of single cells, there has been little attention on drug penetration or distribution in solid tumor tissues. It is reported that the factors that obstruct the penetration and distribution of drugs in solid tumors are closely related to the microenvironment of solid tumors. This review paper aims to discuss the microenvironment that hinders drug penetration in solid tumors and to investigate whether or not changes in the microenvironment can improve drug penetration. This review also introduces in vitro 3D multicellular culture systems that can reproduce the characteristics of solid tumors in vivo and that are required for such studies.

Neurotrophic activity of DA-9801, a mixture extract of Dioscorea japonica Thunb. and Dioscorea nipponica Makino, in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

Dioscorea japonica Thunb. has been traditionally used to treat polyuria and diabetes in Korea.

AIM OF THE STUDY

We previously report the effects of Dioscorea japonica Thunb. extract on glucose control, NGF induction, and neuroprotection in a rodent diabetic model. Since the most potent fraction, DA-9801, was identified from a mixture of Dioscorea japonica Thunb. (DJ) and Dioscorea nipponica Makino (DN) following bioactivity-guided fractionation, here, we investigated the potential mechanism of the extract activity against diabetic peripheral neuropathy (DPN).

MATERIALS AND METHODS

A 1:3 mixture of DJ and DN was extracted with ethanol (DA-9801) and further fractionated into an ethylacetate-soluble fraction (DA-9801E). Effects of these extracts on neurite outgrowth were measured in PC-12 cells and DRG neurons. Effects on cell viability and TrkA phosphorylation were evaluated in PC-12 cells. NGF induction effect was determined in primary Schwann cells as well as IMS32 cells (immortalized Schwann cells).

RESULTS

No cytotoxicity was observed in PC-12 cells at the concentration below 500 μg/ml of either DA-9801 or DA-9801E. DA-9801 and DA-9801E at 100 μg/ml and 10 μg/ml, respectively, showed a significant effect on neurite outgrowth in PC-12 cells and DRG neurons in the presence of or absence a low concentration of NGF (2 ng/ml). The Trk-A phosphorylation effect of DA9801 was confirmed in PC-12 cells. An NGF induction effect of these extracts was not detected in either IMS-32 cells, or primary Schwann cells.

CONCLUSIONS

The NGF agonistic activity of DA-9801 and DA-9801E was demonstrated, which may contribute to their neuroprotective effect against DPN. Studies of the detailed mechanism of these extracts as well as identification of the active components are warranted for the development of an anti-DPN drug from DJ and DN.

Penetration of paclitaxel and 5-fluorouracil in multicellular layers of human colorectal cancer cells

Limited efficacy of chemotherapeutic drugs against solid tumors has been attributed to poor drug penetration into tumor tissues. Multicellular layer (MCL) cultures recapitulate barriers to drug penetration and distribution and have been used successfully in the production of clinically relevant data. In the present study, we evaluated the characteristics of paclitaxel (PTX) and 5-fluorouracil (5-FU) penetration and their effects on tissue penetration using MCLs of human colorectal cancer cells (DLD-1 and HT-29) grown in Transwell inserts. Drug concentration in conditioned media after MCL penetration was estimated using % survival of cells exposed to the conditioned media, and the penetration rate was calculated as % drug concentration relative to the expected concentration after penetration of cell-free MCLs. PTX showed limited penetration in both MCLs in contrast to the full penetration seen by 5-FU. The penetration rate measured after 24 h by cytotoxicity of the conditioned media was 40 and 38% in DLD-1 (20 μM) and HT-29 MCLs (1 μM), respectively, at which concentration the conditioned media produced 50% growth inhibition in monolayers. The penetration profile obtained using [14C]-paclitaxel also showed slow and limited penetration with concentration- and cell line-dependency. In HT-29 MCL, full penetration of PTX was obtained at 10 μM after 48 h, whereas only 80% was obtained at 1 μM. In DLD-1 MCLs, penetration of PTX was minimal, especially at 1 μM, showing penetration rates as low as 10 and 20% after 24 and 96 h, respectively. When PTX and 5-FU were allowed to penetrate in sequential combination, no effect on the penetration rate was observed. Overall, our results demonstrated limited penetration of PTX in human colorectal cancer MCLs along with concentration-, time-, and cell line-dependency. Assessment of penetration using cytotoxicity of the conditioned media used in the present study may be useful in early stage screening of anticancer agents for their potential in tissue penetration.

Abstract 3591: Efficacy and distribution of intratumoral paclitaxel given alone or in combination with doxorubicin using hydrogel in nude mice

Intralesional chemotherapy is suggested to improve local tumor control as well as systemic toxicity profile of antitumor agents against solid tumors. Thermosensitive poly-(organophosphazene) hydrogel is a novel injectable polymer that transforms from sol to gel at body temperature. In this study, we evaluated distribution and efficacy of paclitaxel (PTX) when given as intratumoral injection using the hydrogel or solution formulation in human SNU-601 tumor xenograft-bearing nude mice. Following intratumoral injection of 60 mg/kg of PTX, plasma drug concentrations were lower than 0.5 μg/ml(LOQ) for both hydrogel and solution. For PTX tumor concentration, Cmax was 1.2 folds higher and T1/2 3.7 folds longer with hydrogel compared to solution. Over 21d, AUCtumor was 1.5 folds greater in hydrogel compared to solution, indicating greater drug exposure and retention at target site. The antitumor activity of PTX (30 mg/kg) when given alone or in combination with doxorubicin (DOX, 15 mg/kg) was evaluated after intratumoral hydrogel injection in SNU-601 (Td= 21 d) and SNU-398 (Td= 5 d) xenograft models. The synergism between DOX and PTX, independent of dosage form, was observed in SNU-398, but not in SNU-601. No toxicity was observed in hydrogel group in neither single nor combination treatment. For slow-growing SNU-601 tumor, combination of PTX and DOX given in hyrogel mixture showed greater activity than that of solution. In conclusion, poly-(organophosphazene) polymer may be useful in intralesional administration of PTX to achieve greater drug exposure at target site. Also, combination of DOX and PTX, showed a potential for greater antitumor efficacy, which warrants further evaluation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3591.

Synergistic interaction between tetra-arsenic oxide and paclitaxel in human cancer cells in vitro

Similar to arsenic trioxide (As2O3), tetra-arsenic oxide (As4O6, TAO) has shown anti-proliferative and apoptosis-inducing effects against human leukemic and solid tumor cells. In order to assess the increase in efficacy, we evaluated the combinatory interaction of TAO combined with paclitaxel, 5-FU or cisplatin and studied its mechanism of action in the cell lines of human gastric, cervix and head and neck tumors. Two agents were combined at equitoxic ratios based on the IC50 of each drug. Efficacy improvement was evaluated using a combination index and isobologram at 50% inhibition level. Apoptosis induction and expression of apoptosis-related proteins was determined and the effect on microtubule polymerization was monitored. TAO combined with paclitaxel showed synergistic interaction in all three of gastric, cervix and head and neck cancer cell lines. On the other hand, TAO when combined with 5-FU or cisplatin showed an antagonistic interaction in head and neck or cervix cancer cell lines, respectively. Simultaneous treatment with TAO with paclitaxel resulted in an increased percentage of apoptotic cells and a significant increase in PARP cleavage and caspase-3 activation in the gastric and cervix cancer cells compared to TAO alone as well as the antagonistic groups (TAO with 5-FU or cisplatin). TAO suppressed the tubulin polymerization in the presence and absence of paclitaxel in a concentration-dependent manner, suggesting mitotic catastrophe as a potential mechanism of the synergism with paclitaxel. Overall, the present study suggests that TAO may have a greater potential as an anti-cancer agent against human gastric, cervix and head and neck tumors, in combination with paclitaxel. The synergistic interaction with paclitaxel may be associated with increased apoptosis via inhibition of paclitaxel-induced tubulin polymerization. Further detailed studies of combinatory mechanisms and evaluation using in vivo models are warranted.

A simple HPLC method for doxorubicin in plasma and tissues of nude mice

Doxorubicin is a cytotoxic anthracycline that has been used for the treatment of several malignancies. Several HPLC methods have been reported for the quantification of doxorubicin in biological samples. Tissue matrix effect and sample size requirements, however, have been remaining issues for simple and easy-to-adapt analytical methods in small animal experiments. The present study established a simple HPLC method for doxorubicin in plasma and tissues (tumor, heart, spleen, liver, gastrointestinal tract, brain, lung, and kidney) of nude mice. Our method required a small sample volume (100 microL plasma and 10 mg tissue), which made it possible to use each blank tissue for calibration curves. The limit of quantification was 25 ng/mL in plasma and 0.1 to 0.4 microg/mg in other tissues with recovery rates ranging from 52.4 to 95.2%. The linearity, accuracy and precision in all tissues, except gastrointestinal tract (GIT), were found to be acceptable in the range of 25-2000 ng/mL plasma and 0.1-4 ng/mg tissue. This method was used successfully to determine the drug concentration in plasma and tissues of human tumor xenograft-bearing nude mice given intratumoral doxorubicin in a polymeric drug delivery system designed for sustained release. In conclusion, the present method may be useful as a simple and easy-to-adapt, yet, sensitive analytical method of doxorubicin for plasma and tissue pharmacokinetic studies in small animals such as nude mice.

Novel application of multicellular layers culture for in situ evaluation of cytotoxicity and penetration of paclitaxel

Limited drug penetration into tumor tissue is one of the major factors causing clinical drug resistance in human solid tumors. The multicellular layers (MCL) of human cancer cells have been successfully used to study tissue pharmacokinetics of anticancer drugs. The purpose of this study was to develop a direct and simple method to evaluate vitality changes in situ within MCL using calcein-AM. Human colorectal (DLD-1, HT-29) and bladder (HT-1376, J-82) cancer cells were grown in Transwell inserts to form MCL and subjected to paclitaxel exposure. The drug distribution was evaluated using paclitaxel-rhodamine. Photonic attenuation and limited penetration of calcein-AM prevented cellular vitality evaluation on optical sections under confocal microscopy in DLD-1 MCL. However, direct measurement of the fluorescence intensity on frozen sections of MCL allowed successful vitality assessment in more than 80% depth for HT-29 and J-82 MCL and in the upper 40% depth for DLD-1 and HT-1376 MCL. The penetration of paclitaxel-rhodamine was greater in HT-29 than DLD-1 and its distribution pattern was correlated to the spatial profile of vitality deterioration in both MCL, suggesting that tissue penetration may be an important determinant of drug effect in tumors. In conclusion, a novel method for vitality evaluation in situ within MCL was developed using calcein-AM. This method may provide clinically relevant data regarding the spatial pharmacodynamics of anticancer agents within avascular regions of solid tumors.

Anti-tumor activity of heptaplatin in combination with 5-fluorouracil or paclitaxel against human head and neck cancer cells in vitro

Heptaplatin (HTP), a newly developed platinum analog, has been approved for the treatment of gastric cancers in South Korea. In this study we explored the potential of HTP for the treatment of head and neck squamous cell cancers (HNSCC). The anti-proliferative activity of HTP was evaluated in FaDu, a human HNSCC cell line. Combinations of HTP with 5-fluorouracil (5-FU) or paclitaxel (PTX) were determined using combination indexes, and were compared with combinations of cisplatin and 5-FU or PTX. In order to evaluate the transport of HTP into tumor tissue, its penetration through multicell layers (MCLs) of cancer cells was measured. Cisplatin+5-FU and HTP+5-FU showed additive to antagonistic interactions. In terms of the HTP+paclitaxel combination, HTP showed antagonism and additivity at the 50 and 80% growth inhibition levels, respectively. An additive interaction was obtained and apoptosis was increased by 2-fold at both inhibition levels when the combinatorial PTX dose was reduced to 1/10. HTP, but not cisplatin or oxaliplatin (L-OHP), maintained its anti-proliferative activity after MCL penetration at clinically relevant concentrations, which can be attributed to lower protein binding of HTP. In conclusion, the present study suggests that low-dose PTX may sensitize tumor cells to HTP. HTP also showed greater penetration through multilayers of tumor cells compared to cisplatin and L-OHP, which may be an important characteristic for solid tumor treatment. Overall, the present study supports the clinical development of HTP in combination with low-dose PTX against HNSCC.

Clinical pharmacokinetics of oxaliplatin and 5-fluorouracil administered in combination with leucovorin in Korean patients with advanced colorectal cancer

PURPOSE

Oxaliplatin and 5-fluorouracil (5-FU) act synergistically in colorectal cancer. Here, we evaluated the pharmacokinetics of oxaliplatin and 5-FU administered in combination with leucovorin in Korean advanced colorectal cancer patients.

METHODS

Nine patients with advanced colorectal cancer were included in this study. The 3-week regimen consisted of oxaliplatin (2-h infusion, 130 mg/m(2)on day 1) followed by 5-FU and leucovorin (2-h infusion, 425 and 20 mg/m(2), respectively, from day 1 to day 5). Blood samples were taken and platinum concentrations in total plasma, plasma ultrafiltrate, and RBCs were determined. Plasma concentrations of 5-FU were also determined.

RESULTS

The C (max) of oxaliplatin was observed at the end of infusion, with mean values of 4.66, 0.84, and 2.69 microg/ml for total plasma, plasma ultrafiltrate, and RBC samples, respectively. C (max) ratios of total/free were significantly higher than those reported in other ethnic groups. An accumulation of platinum was observed in RBCs, but not in total plasma and plasma ultrafiltrate samples. A significant correlation was found between the total body clearance of ultrafiltrable platinum and creatinine clearance. The C (max) of plasma 5-FU ranged from 23.9 to 533.8 ng/ml, indicating large inter-patient pharmacokinetic variations.

CONCLUSIONS

This study shows that pharmacokinetics of oxaliplatin in Korean patients is comparable with that of other ethic groups, except for the higher C (max) ratios of total/free. The C (max) of 5-FU in plasma showed large variations among patients. Antitumor efficacy in Korean advanced colorectal cancer patients given oxaliplatin and 5-FU should be further evaluated with respect to pharmacokinetic variabilities.