Cellular context-dependent interaction between cancer and stellate cells in hetero-type multicellular spheroids of pancreatic tumor.

Heterotypic cell-cell interaction between cancer cells and pancreatic stellate cells (PSCs) within tumor microenvironment is considered as a key mechanism for epithelial-mesenchymal transition (EMT) that triggers disease progression and chemoresistance in pancreatic ductal adenocarcinoma (PDAC). Hence, PSCs should be incorporated into in vitro co-culture models to maximize clinical relevance of data obtained using these models. In this study, we developed hetero-type spheroids of pancreatic cancer cells (ductal carcinoma cells PANC-1 and primacy sarcomatoid adenocarcinoma 36473 cells) and PSCs. Effect of PSC co-culture on the formation and growth of multicellular spheroids was cell-line dependent in that growth stimulation effect appeared in PANC-1/PSC spheroids, but not in 36473/PSC spheroids. Spatial distribution of PSCs within spheroids was also cell-line dependent. It was either confined to the center region (PANC-1) or evenly distributed (36473). Changes in expression levels of E-cadherin and vimentin revealed EMT induction in PANC-1/PSC hetero-type spheroids, but not in 36473/PSC spheroids. Gemcitabine sensitivity was increased partially by PSC co-culture. However, PSCs showed relative resistance to gemcitabine compared to PANC-1 cells in PANC-1/PSC spheroids. Overall, our hetero-type spheroid model can be used to study cancer-stroma interaction and their mechanism and evaluate anticancer drug activity. We demonstrated that stromal effect by PSC co-culture might be cellular context dependent with regard to growth stimulation and EMT induction. Hence, anti-stromal therapy should take these differences into consideration.

Combined KRAS-MAPK pathway inhibitors and HER2-directed drug conjugate is efficacious in pancreatic cancer.

Targeting the mitogen-activated protein kinase (MAPK) cascade in pancreatic ductal adenocarcinoma (PDAC) remains clinically unsuccessful. We aim to develop a MAPK inhibitor-based therapeutic combination with strong preclinical efficacy. Utilizing a reverse-phase protein array, we observe rapid phospho-activation of human epidermal growth factor receptor 2 (HER2) in PDAC cells upon pharmacological MAPK inhibition. Mechanistically, MAPK inhibitors lead to swift proteasomal degradation of dual-specificity phosphatase 6 (DUSP6). The carboxy terminus of HER2, containing a TEY motif also present in extracellular signal-regulated kinase 1/2 (ERK1/2), facilitates binding with DUSP6, enhancing its phosphatase activity to dephosphorylate HER2. In the presence of MAPK inhibitors, DUSP6 dissociates from the protective effect of the RING E3 ligase tripartite motif containing 21, resulting in its degradation. In PDAC patient-derived xenograft (PDX) models, combining ERK and HER inhibitors slows tumour growth and requires cytotoxic chemotherapy to achieve tumour regression. Alternatively, MAPK inhibitors with trastuzumab deruxtecan, an anti-HER2 antibody conjugated with cytotoxic chemotherapy, lead to sustained tumour regression in most tested PDXs without causing noticeable toxicity. Additionally, KRAS inhibitors also activate HER2, supporting testing the combination of KRAS inhibitors and trastuzumab deruxtecan in PDAC. This study identifies a rational and promising therapeutic combination for clinical testing in PDAC patients.

Expression variation of OGG1 and HPRT gene and DNA damage in arsenic exposed industrial workers.

Arsenic exposure alters redox balance, induces DNA damage, and deregulates many genes. OGG1 gene involved in base repair mechanism, for excision of 8-oxoguanine (8-oxoG) from DNA formed as a result of accumulation of ROS in cell. HPRT gene encode transferase enzymes involved in purine recycling mechanism. The main focus of the study was to evaluate the expression variation in HPRT, OGG1 gene expression, and DNA damage of industrial workers. Blood samples of 300 occupational workers were collected from welding, brick kiln, furniture, pesticide, and paint industry (n = 60/industry) to evaluate the expression variation in HPRT, OGG1 gene expression, and DNA damage in blood cells by comet assay along with age and gender matched 300 control individuals. Blood arsenic content was higher (P<0.001) in an industrial group compared to the control. OGG1 and HPRT expression were (P<0.05) downregulated in exposed workers compared to controls. Spearman correlation analysis showed a significant positive correlation between HPRT vs OGG1 (P< 0.0001) in exposed workers compared to controls. Altered expression of both genes was observed between workers with <25years and >25years of age as well as between workers with <10years and >10year exposure. Reduced expression (P<0.05) of both genes and a high extent of DNA damage was evident in exposed smokers compared to respective non-smokers. DNA fragmentation was higher (P<0.05) in the furniture, welding and brick kiln group compared to control, and other industries. The present study suggests that altered expression of OGG1 and HPRT gene induce oxidative stress, showed a negative impact on the recycling of purines leading to DNA damage which increase the vulnerability of workers to carcinogenicity.

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.

The MK2/Hsp27 axis is a major survival mechanism for pancreatic ductal adenocarcinoma under genotoxic stress.

Combination chemotherapies remain the cornerstone treatment for pancreatic ductal adenocarcinoma (PDAC), but de novo and acquired resistance is common. In this study, we aimed to identify and characterize resistance mechanisms to a FIRINOX chemotherapy regimen (a combination of 5-fluorouracil, irinotecan, and oxaliplatin) because it is the most aggressive regimen currently used clinically for patients with PDAC. Using an unbiased reverse-phase protein array, we detected phospho-activation of heat shock protein 27 (Hsp27) as the most up-regulated event after FIRINOX treatment in PDAC cells. Silencing HSP27 by RNA interference or by a small-molecule inhibitor enhanced apoptosis caused by FIRINOX in vitro. Mechanistically, FIRINOX up-regulated tumor necrosis factor­α (TNFα), causing autocrine phosphorylation and activation of transforming growth factor­ß­activated kinase 1 (TAK1), MAPK activated protein kinase 2 (MAPKAPK2 or MK2), and, ultimately, Hsp27. Targeting MK2, the kinase that directly phosphorylates Hsp27, abrogated Hsp27 activation, sensitized PDAC cells to apoptosis, and suppressed SN-38­induced protective autophagy in vitro, in part by blocking phospho-activation of Beclin1. In an autochthonous PDAC mouse model, the MK2 inhibitor ATI-450 decreased PDAC development and progression. When combined with FIRINOX, ATI-450 eliminated most PDAC foci and marked prolonged mouse survival without causing additional toxicity. Last, we found that high phospho-MK2 expression in tumors was associated with poorer survival of patients with PDAC. Our study identified MK2 as a mediator of genotoxic stress­induced activation of prosurvival pathways and provides preclinical support for combining an MK2 inhibitor with FIRINOX-based chemotherapies to treat PDAC.

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.

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-ß1), 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-ß inhibitors further improved sorafenib efficacy in the mixed-cell spheroids, indicating the involvement of TGF-ß 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.

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-ß, 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.

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.