Human Pancreatic Cancer AsPC-1 Cells Research Articles

Design, synthesis and activity evaluation of isopropylsulfonyl-substituted 2,4- diarylaminopyrimidine derivatives as FAK inhibitors for the potential treatment of pancreatic cancer

A series of isopropylsulfonyl-substituted 2,4-diarylaminopyrimidine derivatives were designed and synthesized as FAK inhibitors to evaluate their biological activity against pancreatic cancer. One of the most promising compound, 9h, effectively interfered with FAK-mediated phosphorylation and suppressed the proliferation of human pancreatic cancer AsPC-1 cells with half maximal inhibitory concentration (IC50) values of 0.1165 nM and 0.1596 μM, respectively. In addition, 9h also exhibited relatively low toxicity against immortalized normal human liver L-02 cells, indicating its low hepatotoxicity at an equivalent dosage. Furthermore, the elucidation of the mechanism of action revealed that compound 9h effectively inhibited cell migration and inhibited the proliferation of AsPC-1 by blocking the cell cycle at the G2/M phase. Moreover, 9h also demonstrated efficacy in inhibiting tumor growth in a murine AsPC-1 cell xenograft model at the dosage of 10 mg/kg without losing noticeable body weight. All these findings provide important clues for the identification of potent FAK inhibitors.

Abstract 6367: Activation of vitamin D/VDR signaling reverses gemcitabine resistance of pancreatic cancer cells through inhibition of MUC1 expression

Abstract Objective: Pancreatic ductal adenocarcinoma (PDA) has a dismal prognosis, largely due to its resistance to currently available therapies. Identifying the determinants of and signaling pathways regulating this resistance is essential for the development of effective therapeutic modalities to improve the outcome of PDA. The purpose of this study is to define the role of vitamin D/VDR signaling and underlying mechanisms in PDA pathogenesis and therapeutic resistance. Materials & Methods: We used an unbiased reverse phase protein array (RPPA) to identify Vitamin D3 downstream molecules; we also used a variety of cellular and molecular biological approaches to determine the impact of vitamin D/VDR signaling on the expression of MUC1 mucin and the cellular response to gemcitabine treatment in PDA cells. We used in vivo experimental systems to determine the effect of combination use of gemcitabine with Vitamin D analogue on pancreatic tumorigenicity. Additionally, we used ultra-high resolution mass spectrometry (HRMS) to analyze the relative abundance of intracellular dFdCTP in tumor tissue samples. Results: We identified that MUC1 protein expression was significantly reduced in AsPC-1 human pancreatic cancer cells after treatment with vitamin D3 or its analogue calcipotriol (Cal) by the RPPA analysis, which was further confirmed in MiaPaca-2 and Colo357 pancreatic cancer cells. VDR negatively regulated MUC1 expression in pancreatic cancer cells in both gain- and loss-of-function assays. We established gemcitabine (Gem) resistant AsPC-1-GemR and Colo357-GemR cells and found that AsPC-1-GemR and Colo357-GemR cells had much lower levels of VDR but higher levels of MUC1 protein expression compared to their parental cells, Vitamin D3 or its analogue significantly induced VDR and inhibited MUC1 expression in AsPC-1-GemR and Colo357-GemR cells, and sensitized the resistant cells to gemcitabine treatment. The results of siRNA knockdown experiments indicated that inhibition of MUC1 expression was essential for Cal’s sensitization of PDA cells to Gem treatment in vitro. In keeping with these findings, administration of the Vitamin D3 analogue, paricalcitol (PA) significantly enhanced the therapeutic efficacy of Gem compared to chemotherapy alone in xenograft and syngeneic mouse models of pancreatic cancer without any significant systemic toxicity. The improved combination treatment correlated with increased intratumoral concentration of dFdCTP, the biological active metabolite of gemcitabine. Conclusions: This study reveals a previously unidentified vitamin D/VDR-MUC1 signaling pathway involved in the regulation of gemcitabine resistance of PDA. Our results suggest that combinational therapies which include targeted activation of vitamin D/VDR signaling may improve the outcomes of patients with PDA. Citation Format: Daoyan Wei, Margarete Hafley, Liang Wang, Yi Liu, Peiying Yang, Xiangsheng Zuo, Robert S. Bresalier. Activation of vitamin D/VDR signaling reverses gemcitabine resistance of pancreatic cancer cells through inhibition of MUC1 expression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6367.

Caveolin‐1 increases glycolysis in pancreatic cancer cells and triggers cachectic states

In pancreatic cancer, autocrine insulin-like growth factor-1 (IGF-1) and paracrine insulin stimulate both IGF-1 receptor (IGF1R) and insulin receptor (IR) to increase tumor growth and glycolysis. In pancreatic cancer patients, cancer-induced glycolysis increases hepatic gluconeogenesis, skeletal muscle proteolysis, and fat lipolysis and, thereby, causes cancer cachexia. As a protein coexisting with IGF1R and IR, caveolin-1 (cav-1) may be involved in pancreatic cancer-induced cachexia. We undertook the present study to test this hypothesis. Out of wild-type MiaPaCa2 and AsPC1 human pancreatic cancer cell lines, we created their stable sub-lines whose cav-1 expression was diminished with RNA interference or increased with transgene expression. When these cells were studied in vitro, we found that cav-1 regulated IGF1R/IR expression and activation and also regulated cellular glycolysis. We transplanted the different types of MiaPaCa2 cells in growing athymic mice for 8 weeks, using intact athymic mice as tumor-free controls. We found that cav-1 levels in tumor grafts were correlated with expression levels of the enzymes that regulated hepatic gluconeogenesis, skeletal muscle proteolysis, and fat lipolysis in the respective tissues. When the tumors had original or increased cav-1, their carriers’ body weight gain was less than the tumor-free reference. When cav-1 was diminished in tumors, the tumor carriers’ body weight gain was not changed significantly, compared to the tumor-free reference. In conclusion, cav-1 in pancreatic cancer cells stimulated IGF1R/IR and glycolysis in the cancer cells and triggered cachectic states in the tumor carrier.

ARHGAP25 Inhibits Pancreatic Adenocarcinoma Growth by Suppressing Glycolysis via AKT/mTOR Pathway.

Increasing evidence reveals that the Rho GTPase-activating protein is a crucial negative regulator of Rho family GTPase involved in tumorigenesis. The Rho GTPase-activating protein 25 (ARHGAP25) has been shown to specifically inactivate the Rho family GTPase Rac1, which plays an important role in pancreatic adenocarcinoma (PAAD) progression. Therefore, here we aimed to clarify the expression and functional role of ARHGAP25 in PAAD. The ARHGAP25 expression was lower in PAAD tissues than that in normal pancreatic tissues based on bioinformatics analysis and immunohistochemistry staining. Overexpression of ARHGAP25 inhibited cell growth of AsPC-1 human pancreatic cancer cells in vitro, while opposite results were observed in BxPC-3 human pancreatic cancer cells with ARHGAP25 knockdown. Consistently, in vivo tumorigenicity assays also confirmed that ARHGAP25 overexpression suppressed tumor growth. Mechanically, overexpression of ARHGAP25 inactivated AKT/mTOR signaling pathway by regulating Rac1/PAK1 signaling, which was in line with the results from the Gene set enrichment analysis on The Cancer Genome Atlas dataset. Furthermore, we found that ARHGAP25 reduced HIF-1α-mediated glycolysis in PAAD cells. Treatment with PF-04691502, a dual PI3K/mTOR inhibitor, hampered the increased cell growth and glycolysis due to ARHGAP25 knockdown in PAAD cells. Altogether, these results conclude that ARHGAP25 acts as a tumor suppressor by inhibiting the AKT/mTOR signaling pathway, which might provide a therapeutic target for PAAD.

Mint3 depletion restricts tumor malignancy of pancreatic cancer cells by decreasing SKP2 expression via HIF-1

Pancreatic cancer is one of the most fatal cancers without druggable molecular targets. Hypoxia inducible factor-1 (HIF-1) is a heterodimeric transcriptional factor that promotes malignancy in various cancers including pancreatic cancer. Herein, we found that HIF-1 is accumulated in normoxic or moderate hypoxic areas of pancreatic cancer xenografts in vivo and is active even during normoxia in pancreatic cancer cells in vitro. This prompted us to analyze whether the HIF-1 activator Mint3 contributes to malignant features of pancreatic cancer. Mint3 depletion by shRNAs attenuated HIF-1 activity during normoxia and cell proliferation concomitantly with accumulated p21 and p27 protein in pancreatic cancer cells. Further analyses revealed that Mint3 increased transcription of the oncogenic ubiquitin ligase SKP2 in pancreatic cancer cells via HIF-1. This Mint3-HIF-1-SKP2 axis also promoted partial epithelial-mesenchymal transition, stemness features, and chemoresistance in pancreatic cancer cells. Even in vivo, Mint3 depletion attenuated tumor growth of orthotopically inoculated human pancreatic cancer AsPC-1 cells. Database and tissue microarray analyses showed that Mint3 expression is correlated with SKP2 expression in human pancreatic cancer specimens and high Mint3 expression is correlated with poor prognosis of pancreatic cancer patients. Thus, targeting Mint3 may be useful for attenuating the malignant features of pancreatic cancer.

Dehydroabietic oximes halt pancreatic cancer cell growth in the G1 phase through induction of p27 and downregulation of cyclin D1

Low 5-year survival rates, increasing incidence, as well as the specific challenges of targeting pancreatic cancer, clearly support an urgent need for new multifunctional drugs for the prevention and treatment of this fatal disease. Natural products, such as abietane-type diterpenoids, are widely studied as promiscuous anticancer agents. In this study, dehydroabietic oximes were identified as potential compounds to target pancreatic cancer and cancer-related inflammation. The compounds inhibited the growth of human pancreatic cancer Aspc-1 cells with IC50 values in the low micromolar range and showed anti-inflammatory activity, measured as the inhibition of nitric oxide production, an important inflammatory mediator in the tumour microenvironment. Further studies revealed that the compounds were able to induce cancer cell differentiation and concomitantly downregulate cyclin D1 expression with upregulation of p27 levels, consistent with cell cycle arrest at the G1 phase. Moreover, a kinase profiling study showed that one of the compounds has isoform-selective, however modest, inhibitory activity on RSK2, an AGC kinase that has been implicated in cellular invasion and metastasis.

Docetaxel-polymeric nanoparticle enhances radiotherapeutic efficacy in human pancreatic cancer

Background: Nanoparticle therapeutics is promising platform for cancer treatment. In our previous study, we have developed polymeric nanoparticles (PNP) in which docetaxel was incorporated to reduce the side effects and improve the therapeutic efficacy, and recently finished its phase 1 clinical study in patients with solid tumors. Methods: Radiotherapeutic efficacy of the docetaxel-contained PNP (DTX-PNP) in pancreatic cancer cells was determined by both in vitro and in vivo assay such as clonogenic survival assay with cancer cell lines, western blot for apoptotic cell death and tumor growth inhibition assay using several kinds of xenograft models. The tumors derived from human pancreatic cancer AsPC-1 or BxPC-3 cells were analyzed by immunohistochemistry (IHC) to detect in apoptosis and tubulin polymerization induced by DTX-PNP. The combinational therapeutic effect of DTX-PNP and ionizing radiation (IR) was evaluated in vivo mice models of AsPC-1 or BxPC-3 cell line-derived xenograft models and patient-derived xenograft model, and compared to that of reference drugs. Results: DTX-PNP in combination with IR showed high cytotoxicity to pancreatic cancer cells, and ultimate inhibition of cell proliferation as determined via in vitro assays. In vivo radiotherapeutic efficacy was markedly enhanced by intravenous injection of DTX-PNP comparing to Gemzar, a common chemoradiation therapeutic agent in pancreatic cancer. Conclusions: These results suggested DTX-PNP can hold an invaluable and promising position in treating human pancreatic cancer as a novel and effective radiosensitizing agent.

Enoxacin with UVA Irradiation Induces Apoptosis in the AsPC1 Human Pancreatic Cancer Cell Line Through ROS Generation.

Pancreatic cancer is one of the deadliest human cancers. In the current study, we investigated the possibility of a new treatment strategy using a combination of the new fluoroquinolone, enoxacin, and mild ultraviolet A (UVA) irradiation. Enoxacin with UVA irradiation increased the number of annexin V-positive (apoptotic) pancreatic cancer cells in time- and concentration-dependent manners, whereas alone neither had these effects. In addition, enoxacin with UVA irradiation induced cleavage of poly (ADP-ribose) polymerase in AsPC1 human pancreatic cancer cells. Moreover, the singlet oxygen scavengers, histidine and sodium azide, and the hydroxyl radical scavenger, mannitol, significantly suppressed apoptosis induced by enoxacin and UVA irradiation, respectively. These results suggest that UVA irradiation activates enoxacin, after which activated enoxacin induces apoptosis of AsPC1 cells through generation of reactive oxygen species. Therefore, the combination of enoxacin with mild UVA irradiation may be a useful method for treating pancreatic cancer.

Targeted pancreatic cancer drug-delivery utilizing sigma-2 ligand/receptor internalization is energy-dependent.

331 Background: Pancreatic cancer is a devastating disease that is poorly responsive to traditional systemic therapies. Cancer-selective drug delivery can improve survival and reduce systemic toxicities. We have developed a pancreatic cancer drug delivery platform based on sigma-2 receptor ligands conjugated to small molecule drug cargos, which improves delivery and efficacy through efficient drug internalization. However, the mechanism of drug internalization via the sigma-2 receptor/ligand interaction remains unclear. Methods: Uptake of fluorescently conjugated sigma-2 ligand SW120 was studied in ASPC-1 human pancreatic cancer cells. Uptake was measured at 37C, 4C, after competitive inhibition with sigma-2 ligand SW43, and after pretreatment with Pitstop 2 (Abcam), an inhibiter of clathrin-mediated endocytosis. Uptake was visualized using live-cell imaging using A1Rsi confocal laser scanning microscope (Nikon). Image analysis was performed using FIJI (NIH) and Matlab (Mathworks). Results: SW120 (10 nM) was rapidly internalized into ASPC-1 cells at 37C with maximal fluorescence at 12 minutes. As a negative control, incubation of ASPC-1 cells with the unconjugated flourophore NBD Cl demonstrated no uptake after 15 minutes, indicating that uptake of SW120 depends on the specific sigma-2 receptor/ligand interaction. Fluorescence at 15 minutes was reduced by 85% in ASPC-1 cells incubated at 4C, indicating uptake of SW120 into cells is an energy dependent process. Pretreatment of cells with Pitstop 2 decreased total flourescence at 15 minutes by 76%, suggesting an important role of clathrin-mediated endocytosis in sigma-2 receptor uptake, while pretreatment with competitive inhibitor SW43 reduced uptake by 84%, suggesting that sigma-2 ligands are internalized via a specific receptor capable of saturation. Conclusions: Sigma-2 receptor ligands are rapidly internalized into pancreatic cancer cells via a specific, targetable, energy-dependent pathway that appears to rely on clathrin-mediated endocytosis. Further understanding of sigma-2 mediated drug internalization can help optimize targeted drug development and delivery for pancreatic cancer patients.

Depletion of pro-oncogenic RUNX2 enhances gemcitabine (GEM) sensitivity of p53-mutated pancreatic cancer Panc-1 cells through the induction of pro-apoptotic TAp63.

Recently, we have described that siRNA-mediated silencing of runt-related transcription factor 2 (RUNX2) improves anti-cancer drug gemcitabine (GEM) sensitivity of p53-deficient human pancreatic cancer AsPC-1 cells through the augmentation of p53 family TAp63-dependent cell death pathway. In this manuscript, we have extended our study to p53-mutated human pancreatic cancer Panc-1 cells. According to our present results, knockdown of mutant p53 alone had a marginal effect on GEM-mediated cell death of Panc-1 cells. We then sought to deplete RUNX2 using siRNA in Panc-1 cells and examined its effect on GEM sensitivity. Under our experimental conditions, RUNX2 knockdown caused a significant enhancement of GEM sensitivity of Panc-1 cells. Notably, GEM-mediated induction of TAp63 but not of TAp73 was further stimulated in RUNX2-depleted Panc-1 cells, indicating that, like AsPC-1 cells, TAp63 might play a pivotal role in the regulation of GEM sensitivity of Panc-1 cells. Consistent with this notion, forced expression of TAp63α in Panc-1 cells promoted cell cycle arrest and/or cell death, and massively increased luciferase activities driven by TAp63-target gene promoters such as p21WAF1 and NOXA. In addition, immunoprecipitation experiments indicated that RUNX2 forms a complex with TAp63 in Panc-1 cells. Taken together, our current observations strongly suggest that depletion of RUNX2 enhances the cytotoxic effect of GEM on p53-mutated Panc-1 cells through the stimulation of TAp63-dependent cell death pathway even in the presence of a large amount of pro-oncogenic mutant p53, and might provide an attractive strategy to treat pancreatic cancer patients with p53 mutations.

Bis(acetylacetonato)-oxidovanadium(IV) and sodium metavanadate inhibit cell proliferation via ROS-induced sustained MAPK/ERK activation but with elevated AKT activity in human pancreatic cancer AsPC-1 cells.

In this study, the antiproliferative effect of bis(acetylacetonato)-oxidovanadium(IV) and sodium metavanadate and the underlying mechanisms were investigated in human pancreatic cancer cell line AsPC-1. The results showed that both exhibited an antiproliferative effect through inducing G2/M cell cycle arrest and can also cause elevation of reactive oxygen species (ROS) levels in cells. Moreover, the two vanadium compounds induced the activation of both PI3K/AKT and MAPK/ERK signaling pathways dose- and time-dependently, which could be counteracted with the antioxidant N-acetylcysteine. In the presence of MEK-1 inhibitor, the degradation of Cdc25C, inactivation of Cdc2 and accumulation of p21 were relieved. However, the treatment of AKT inhibitor did not cause any significant effect. Therefore, it demonstrated that the ROS-induced sustained MAPK/ERK activation rather than AKT contributed to vanadium compounds-induced G2/M cell cycle arrest. The current results also exhibited that the two vanadium compounds did not induce a sustained increase of ROS generation, but the level of ROS reached a plateau instead. The results revealed that an intracellular feedback loop may be against the elevated ROS level induced by vanadate or VO(acac)2, evidenced by the increased GSH content, the unchanged level at the expression of antioxidant enzymes. Therefore, vanadium compounds can be regarded as a novel type of anticancer drugs through the prolonged activation of MAPK/ERK pathway but retained AKT activity. The present results provided a proof-of-concept evidence that vanadium-based compounds may have the potential as both antidiabetic and antipancreatic cancer agents to prevent or treat patients suffering from both diseases.

A sesquiterpene lactone from Siegesbeckia glabrescens suppresses Hedgehog/Gli-mediated transcription in pancreatic cancer cells.

Pancreatic cancer is aggressive and therefore difficult to treat; however, continued efforts have been made with the aim of developing an effective therapy against the disease. The Hedgehog (Hh) signaling pathway is reportedly involved in the proliferation and survival of pancreatic cancer cells. The transcription factor glioma-associated oncogene (Gli) is a key component of the Hh signaling pathway and the primary effector of pancreatic cancer development. Inhibiting Gli is a proven therapeutic strategy for this disease. The present study examined the regulation of Gli and the expression of its target genes to identify an inhibitor of the Sonic Hh (Shh) pathway. A germacranolide sesquiterpene lactone (GSL) was isolated from Siegesbeckia glabrescens as an inhibitor of Gli-mediated transcription. The results demonstrated that GSL inhibited Shh-induced osteoblast differentiation and Gli homolog 1 (Gli1)-mediated transcriptional activity in mesenchymal C3H10T1/2 stem cells. Furthermore, GSL suppressed Gli-mediated transcriptional activity in human pancreatic cancer PANC-1 and AsPC-1 cells, which resulted in reduced cancer cell proliferation and downregulated expression of the Gli-target genes, Gli1 and cyclin D1. A sesquiterpene lactone from S. glabrescens may therefore serve as a candidate for the treatment of Hh/Gli-dependent pancreatic cancer.

DUSP28 links regulation of Mucin 5B and Mucin 16 to migration and survival of AsPC-1 human pancreatic cancer cells.

The prognosis of pancreatic cancer has not improved despite considerable and continuous effort. Dual-specificity phosphatase 28 (DUSP28) is highly expressed in human pancreatic cancers and exerts critical effects. However, knowledge of its function in pancreatic cancers is extremely limited. Here, we demonstrate the peculiar role of DUSP28 in pancreatic cancers. Analysis using the Gene Expression Omnibus public microarray database indicated higher DUSP28, MUC1, MUC4, MUC5B, MUC16 and MUC20 messenger RNA (mRNA) levels in pancreatic cancers compared with normal pancreas tissues. DUSP28 expression in human pancreatic cancer correlated positively with those of MUC1, MUC4, MUC5B, MUC16 and MUC20. In contrast, there were no significant correlations between DUSP28 and mucins in normal pancreas tissues. Decreased DUSP28 expression resulted in down-regulation of MUC5B and MUC16 at both the mRNA and protein levels; furthermore, transfection with small interfering RNA (siRNA) for MUC5B and MUC16 inhibited the migration and survival of AsPC-1 cells. In addition, transfection of siRNA for MUC5B and MUC16 resulted in a significant decrease in phosphorylation of FAK and ERK1/2 compared with transfection with scrambled-siRNA. These results collectively indicate unique links between DUSP28 and MUC5B/MUC16 and their roles in pancreatic cancer; moreover, they strongly support a rationale for targeting DUSP28 to inhibit development of malignant pancreatic cancer.

Impact of down-regulation of histone methyltransferase enhancer of zeste homolog 2 on RUNX3 expressions, proliferation and apoptosis in human pancreatic cancer

Objective To investigate the impact of down-regulation of histone methyltransferase enhancer of zeste homolog 2 (EZH2) on RUNX3 expressions, proliferation and apoptosis in human pancreatic cancer. Methods The expressions of EZH2 and RUNX3 in 38 pancreatic cancer patients and human pancreatic cancer AsPC-1, PANC-1 and BxPC-3 cells were detected by immunohistochemistry and western blot, respectively. Cells were transfected with siEZH2 by lipofectamin 2000. Real time-PCR and western blot were used to detect EZH2 and RUNX3 expressions. Cell growth and apoptosis in vitro and vivo were assessed by MTT, flow cytometry and nude mice experiments, respectively. The correlation among the expressions of EZH2, clinical pathological features and overall survival rate were analyzed. Results Elevated EZH2 and decreased RUNX3 expressions were observed in human pancreatic cancer tissues and cells (P<0.05). Knockdown of EZH2 reduced cell growth and induced apoptosis in vitro and vivo by upregulating RUNX3 protein expression (P<0.05). In addition, the EZH2 expressions were correlated with tumor stage, lymph node metastasis and poor prognosis (P<0.05). Conclusions EZH2 expressions were correlated with malignancy and poor prognosis in pancreatic cancer. Tumor cell proliferation was promoted by EZH2 through down-regulation of RUNX3. EZH2 may be a potential therapeutic target for pancreatic cancer. Key words: Pancreatic cancer; Gene, EZH2; Cancer suppressor gene, RUNX3; Apoptosis; Prognosis

Silencing of RUNX2 enhances gemcitabine sensitivity of p53-deficient human pancreatic cancer AsPC-1 cells through the stimulation of TAp63-mediated cell death.

It has been well-known that human pancreatic cancer represents the fourth and fifth leading causes of cancer-related deaths in the United States and Japan, respectively.1, 2 Notably, pancreatic cancer is characterized by high metastatic potential, resistance to chemotherapy and thus its prognosis is extremely poor with 5-year survival <5%. At diagnosis, more than 80% cases are already advanced and non-resectable.3 Therefore, chemotherapy and/or radiotherapy is the only option. Despite improvements in the treatments, the survival rate has not been significantly ameliorated over the last few decades. For chemotherapy, a deoxycytidine analog termed gemcitabine (GEM) is the first line of standard treatment given to most of the patients bearing advanced pancreatic cancer.4 Unfortunately, GEM treatment provides limited clinical benefits, especially in advanced and metastatic disease.5 Hence, the extensive efforts to clarify the precise molecular mechanisms behind GEM-resistant phenotype of malignant pancreatic cancer and also to develop the promising strategies to enhance the efficacy of GEM should be required.

Hyaluronic acid-conjugated polyamidoamine dendrimers for targeted delivery of 3,4-difluorobenzylidene curcumin to CD44 overexpressing pancreatic cancer cells

The current study was aimed to develop a targeted dendrimer formulation of 3, 4-difluorobenzylidene curcumin (CDF) and evaluate its potential in CD44 targeted therapy for pancreatic cancer. Using amine terminated fourth generation poly(amidoamine) (PAMAM) dendrimer nanocarrier and hyaluronic acid (HA) as a targeting ligand, we engineered a CD44-targeted PAMAM dendrimer (HA-PAMAM) formulation of CDF. The resulting dendrimer nanosystem (HA-PAMAM-CDF) had a particle size and surface charge of 9.3±1.5nm and −7.02±9.53mV, respectively. When CD44 receptor overexpressing MiaPaCa-2 and AsPC-1 human pancreatic cancer cells were treated with HA-PAMAM-CDF, a dose-dependent cytotoxicity was observed. Furthermore, blocking the CD44 receptors present on the MiaPaCa-2 cells using free excess soluble HA prior to treatment with HA-PAMAM-CDF nano-formulation resulted in 1.71 fold increase in the IC50 value compared to non-targeted formulation (PAMAM-CDF), confirming target specificity of HA-PAMAM-CDF. Additionally, HA-PAMAM-CDF formulation when compared to PAMAM-CDF, displayed higher cellular uptake in MiaPaCa-2 cancer cell lines as shown by fluorescence studies. In summary, the novel CD44 targeted dendrimer based nanocarriers appear to be proficient in mediating site-specific delivery of CDF via CD44 receptors, with an improved therapeutic margin and safety.

Hyaluronic Acid Engineered Nanomicelles Loaded with 3,4-Difluorobenzylidene Curcumin for Targeted Killing of CD44+ Stem-Like Pancreatic Cancer Cells.

Cancer stem-like cells (CSLCs) play a pivotal role in acquiring multidrug resistant (MDR) phenotypes. It has been established that pancreatic cancers overexpressing CD44 receptors (a target of hyaluronic acid; HA) is one of the major contributors for causing MDR. Therefore, targeted killing of CD44 expressing tumor cells using HA based active targeting strategies may be beneficial for eradicating MDR-pancreatic cancers. Here, we report the synthesis of a new HA conjugate of copoly(styrene maleic acid) (HA-SMA) that could be engineered to form nanomicelles with a potent anticancer agent, 3,4-difluorobenzylidene curcumin (CDF). The anticancer activity of CDF loaded nanomicelles against MiaPaCa-2 and AsPC-1 human pancreatic cancer cells revealed dose-dependent cell killing. Results of cellular internalization further confirmed better uptake of HA engineered nanomicelles in triple-marker positive (CD44+/CD133+/EpCAM+) pancreatic CSLCs compared with triple-marker negative (CD44-/CD133-/EpCAM-) counterparts. More importantly, HA-SMA-CDF exhibited superior anticancer response toward CD44+ pancreatic CSLCs. Results further confirmed that triple-marker positive cells treated with HA-SMA-CDF caused significant reduction in CD44 expression and marked inhibition of NF-κB that in-turn can mitigate their proliferative and invasive behavior. Conclusively, these results suggest that the newly developed CD44 targeted nanomicelles may have great implications in treating pancreatic cancers including the more aggressive pancreatic CSLCs.

Silencing of RUNX2 enhances gemcitabine sensitivity of p53-deficient human pancreatic cancer AsPC-1 cells through the stimulation of TAp63-mediated cell death.

Runt-related transcription factor 2 (RUNX2) has been considered to be one of master regulators for osteoblast differentiation and bone formation. Recently, we have described that RUNX2 attenuates p53/TAp73-dependent cell death of human osteosarcoma U2OS cells bearing wild-type p53 in response to adriamycin. In this study, we have asked whether RUNX2 silencing could enhance gemcitabine (GEM) sensitivity of p53-deficient human pancreatic cancer AsPC-1 cells. Under our experimental conditions, GEM treatment increased the expression level of p53 family TAp63, whereas RUNX2 was reduced following GEM exposure, indicating that there exists an inverse relationship between the expression level of TAp63 and RUNX2 following GEM exposure. To assess whether TAp63 could be involved in the regulation of GEM sensitivity of AsPC-1 cells, small interfering RNA-mediated knockdown of TAp63 was performed. As expected, silencing of TAp63 significantly prohibited GEM-dependent cell death as compared with GEM-treated non-silencing cells. As TAp63 was negatively regulated by RUNX2, we sought to examine whether RUNX2 knockdown could enhance the sensitivity to GEM. Expression analysis demonstrated that depletion of RUNX2 apparently stimulates the expression of TAp63, as well as proteolytic cleavage of poly ADP ribose polymerase (PARP) after GEM exposure, and further augmented GEM-mediated induction of p53/TAp63-target genes, such as p21WAF1, PUMA and NOXA, relative to GEM-treated control-transfected cells, implying that RUNX2 has a critical role in the regulation of GEM resistance through the downregulation of TAp63. Notably, ablation of TAp63 gave a decrease in number of γH2AX-positive cells in response to GEM relative to control-transfected cells following GEM exposure. Consistently, GEM-dependent phosphorylation of ataxia telangiectasia-mutated protein was remarkably impaired in TAp63 knockdown cells. Collectively, our present findings strongly suggest that RUNX2-mediated repression of TAp63 contributes at least in part to GEM resistance of AsPC-1 cells, and thus silencing of RUNX2 may be a novel strategy to enhance the efficacy of GEM in p53-deficient pancreatic cancer cells.

Construction of orthotopic xenograft mouse models for human pancreatic cancer.

Animal models are indispensable for the study of tumorigenesis and the development of anti-cancer drugs for human pancreatic cancer. In the present study, two orthotopic xenograft mouse models were developed. AsPC-1 human pancreatic cancer cells were stably labeled with red fluorescent protein (RFP) and injected subcutaneously into nude mice. For the orthotopic tumor mass model, the formed subcutaneous tumors were cut into blocks and implanted into the pancreas of nude mice via laparotomy. For the Matrigel™ tumor block model, solidified Matrigel containing RFP-labeled AsPC-1 cells was cut into blocks and implanted into the pancreas of nude mice. A subcutaneous tumor xenograft model was used as a control. Tumor growth and metastasis were assessed using an in vivo fluorescence imaging system. Thirty-six days after implantation, all mice from the two orthotopic xenograft models (n=20 per group) and 55% of the subcutaneous xenograft mice (n=20) developed tumors. The tumor growth rate was significantly higher in the orthotopic models than that in the subcutaneous model (P<0.01). Metastasis to organs such as the liver was observed in the orthotopic tumor models. Histological examination showed that the tumors were poorly differentiated adenocarcinomas. In conclusion, two orthotopic xenograft mouse models of human pancreatic cancer were established; these exhibited greater tumor growth and metastasis than the subcutaneous xenograft mouse model.

Antagonism of microRNA-99a promotes cell invasion and down-regulates E-cadherin expression in pancreatic cancer cells by regulating mammalian target of rapamycin

MicroRNA-99a (miRNA-99a), a potential tumor suppressor, has been implicated in tumorigenesis of many human malignancies. However, the role of miRNA-99a in pancreatic cancer remains unclear. In the present study, we transfected miRNA-99a antagonism into human pancreatic cancer AsPC-1 cells to inhibit miRNA-99a expression and investigated its influence on cell migration and invasion as well as the underlying possible mechanisms. We found that miRNA-99a antagonism significantly increased proliferation, migration and invasion abilities of AsPC-1 cells, which was accompanied by increased expression of mesenchymal phenotype cell biomarkers (N-cadherin, Vimentin, and α-SMA), and decreased expression of epithelial phenotype cell biomarker (E-cadherin). Interestingly, small interfering RNA (siRNA)-mediated knockdown of mammalian target of rapamycin (mTOR) remarkably restored miRNA-99a antagonism-induced down-regulation of E-cadherin. In conclusion, our data suggest that miRNA-99a is involved in pancreatic cancer migration and invasion by regulating mTOR, and may provide a target for effective therapies against pancreatic cancer.