Mechanisms of drug resistance in colon cancer and its therapeutic strategies

The Role of Extracellular Vesicles as Modulators of the Tumor Microenvironment, Metastasis and Drug Resistance in Colorectal Cancer

Colorectal cancer (CRC) is one of the most common cancers worldwide, with high morbidity and mortality rates. A number of factors including modulation of the tumor microenvironment, high metastatic capability, and resistance to treatment have been associated with CRC disease progression. Recent studies have documented that tumor-derived extracellular vesicles (EVs) play a significant role in intercellular communication in CRC via transfer of cargo lipids, proteins, DNA and RNAs to the recipient tumor cells. This transfer influences a number of immune-related pathways leading to activation/differentiation/expression of immune cells and modulation of the tumor microenvironment that plays a significant role in CRC progression, metastasis, and drug resistance. Furthermore, tumor-derived EVs are secreted in large amounts in biological fluids of CRC patients and as such the expression analysis of EV cargoes have been associated with prognosis or response to therapy and may be a source of therapeutic targets. This review aims to provide a comprehensive insight into the role of EVs in the modulation of the tumor microenvironment and its effects on CRC progression, metastasis, and drug resistance. On the other hand, the potential role of CRC derived EVs as a source of biomarkers of response and therapeutic targets will be discussed in detail to understand the dynamic role of EVs in CRC diagnosis, treatment, and management.

Development of a Colorectal Cancer 3D Micro-tumor Construct Platform From Cell Lines and Patient Tumor Biospecimens for Standard-of-Care and Experimental Drug Screening

Colorectal cancer is subject to a high rate of mutations, with late stage tumors often containing many mutations. These tumors are difficult to treat, and even with the recently implemented methods of personalized medicine at modern hospitals aiming to narrow treatments, a gap still exists. Proper modeling of these tumors may help to recommend optimal treatments for individual patients, preferably utilizing a model that maintains proper signaling in respect to the derived parent tissue. In this study, we utilized an extracellular matrix-derived hydrogel to create a 3D micro-tumor construct platform capable of both supporting cells for long time durations and for high throughput drug screening. Experiments with cell lines demonstrated long-term viability with maintenance of cell proliferation. Furthermore, studies with several chemotherapeutics utilizing different mechanisms of action displayed differences in efficacy in comparing 3D and 2D cultures. Finally, patient colorectal tumor tissue was acquired and employed to reconstruct micro-tumor constructs, providing a system for the testing of novel chemotherapeutics against tumors in a patient-specific manner. Collectively, the results describe a system capable of high throughput testing while maintaining important characteristics of the parent tissue.

The role of photodynamic therapy on multidrug resistant breast cancer

Breast cancer heterogeneity allows cells with different phenotypes to co-exist, contributing to treatment failure and development of drug resistance. In addition, abnormal signal transduction and dysfunctional DNA repair genes are common features with breast cancer resistance. Chemo-resistance of breast cancer associated with multidrug resistance events utilizes ATP-binding cassette (ABC) efflux transporters to decrease drug intracellular concentration. Photodynamic therapy (PDT) is the treatment that involves a combination of a photosensitizer (PS), light and molecular oxygen to induce cell death. This treatment modality has been considered as a possible approach in combatting multidrug resistance phenomenon although its therapeutic potential towards chemo-resistance is still unclear. Attempts to minimize the impact of efflux transporters on drug resistance suggested concurrent use of chemotherapy agents, nanotechnology, endolysosomal release of drug by photochemical internalization and the use of structurally related compound inhibitors to block the transport function of the multidrug resistant transporters. In this review, we briefly summarize the role of membrane ABC efflux transporters in therapeutic outcomes and highlight research findings related to PDT and its applications on breast cancer with multidrug resistance phenotype. With the development of an ideal PS for photodynamic cancer treatment, it is possible that light activation may be used not only to sensitize the tumour but also to enable release of PS into the cytosol and as such bypass efflux membrane proteins and inhibit escape pathways that may lead to resistance.

Coelomic Fluid of Lumbricus rubellus Synergistically Enhances Cytotoxic Effect of 5-Fluorouracil through Modulation of Focal Adhesion Kinase and p21 in HT-29 Cancer Cell Line

Coelomic fluid of Lumbricus rubellus (CFL) has attracted interest due to its pharmacological properties, including antitumor effect. Furthermore, it is necessary to evaluate the response to treatment with new cancer therapeutic agents. This study aims to investigate whether the combination of CFL and 5-fluorouracil could reduce FAK protein level and iCa²⁺ and enhance p21 level. Furthermore, it is necessary to evaluate the response to treatment with new cancer therapeutic agents. After 24 hours of treatment, it was necessary to assess the percentage of apoptosis, FAK, and p21 protein expression by flow cytometry. iCa²⁺ concentration was measured using immunofluorescence. The combination therapy of CFL with 5-fluorouracil potently suppressed six treatment groups were included in this study. HT-29 cell lines were cultured and divided into six groups: group 1 was treated with vehicle (negative control), groups 2-5 were treated with 5-fluorouracil, groups 3-5 were treated with either CFL 5, 10, or 20 µg/ml immediately after 5-fluorouracil, and group 6 was treated with CFL 20 µg/ml, the progression of colorectal cancer. Combination of CFL and 5-fluorouracil significantly decreased FAK expression (p<0.05), iCa²⁺ (p<0.05), and increased p21 expression (p<0.05) in HT-29 cells. Our results suggest that CFL has an anticancer potential in colorectal cancer when combined with 5-fluorouracil.

Xanthium strumarium´s xanthatins induces mitotic arrest and apoptosis in CT26WT colon carcinoma cells

BACKGROUND

Colorectal cancer is one of the most common malignancies worldwide and is associated with high mortality rates. We previously reported that Xanthium strumarium L. induces mitotic arrest in proliferating cells, a process mediated by xanthatins.

HYPOTHESIS/AIM

The aim of this work is to study if xanthatins, isolated from X. strumarium total extract, affect the proliferative capacity of CT26WT colon cancer cells and, in consequence, if tumor growth and proliferation of (lung) metastatic sites can also be arrested in vivo.

STUDY DESIGN

This study consisted of both in vitro and in vivo experiments involving the CT26WT cell line and a subcutaneous mouse model of colon cancer. In vitro cell cycle progression, in vivo tumoral growth and anti-metastatic activity were analyzed to investigate whether xanthatins of X. strumarium induce mitotic arrest in proliferating colorectal carcinoma.

RESULTS

Our in vitro results show that X. strumarium, mediated by xanthatins, induces G₂/M arrest and impair anaphase entrance. This leads to a significant induction of apoptotic and necrotic in CT26WT cells, demonstrating their significant anti-proliferative activity through interfering with the mitotic apparatus. Furthermore, our in vivoresults reveal that X. strumarium inhibits both tumor growth and metastasis progression.

CONCLUSION

X. strumarium antitumor activities are mainly mediated by xanthatins through inhibition of tumor growth and metastasis, inducing mitotic arrest and apoptosis in colon carcinoma cells. These findings further confirm the therapeutic potential of X. strumarium in colorectal cancer.

AKT2 phosphorylation of hexokinase 2 at T473 promotes tumorigenesis and metastasis in colon cancer cells via NF-κB, HIF1α, MMP2, and MMP9 upregulation

It has been well-established that AKT2 plays an important role in the development and progression of colon cancer; however, its precise function remains unclear. In the present study, we found that AKT2 can interact with and phosphorylate hexokinase 2 (HK2), the rate-limiting enzyme in glycolysis. Moreover, threonine phosphorylation dramatically increases its catalytic activity and enhances glycolysis. Mechanistically, AKT2 phosphorylation of HK2 at T473 was found to increase hexokinase activity and lactic acid production. A mutation in the AKT2 phosphorylation site of HK2 substantially reduced the stimulating effects of AKT2 on glycolysis, cellular apoptosis, invasion, tumorigenesis, and metastasis. In addition, AKT2 regulated NF-κB, HIF1Α, MMP2, and MMP9 via the phosphorylation of HK2 at the T473 site. Taken together, AKT2 increases the invasion, tumorigenesis, and metastasis of colon cancer cells in vitro and promotes lung metastasis in nude mice in vivo through the phosphorylation of the T473 site of HK2 by upregulating NF-κB, HIF1α, MMP2, and MMP9. In conclusion, our findings highlight a novel mechanism for the AKT2-HK2-NF-κB/HIF1α/MMP2/MMP9 axis in the regulation of colon cancer progression. Moreover, our results suggest that both AKT2 and HK2 may be potential targets for the treatment of colon cancer.

Selected Aspects of Chemoresistance Mechanisms in Colorectal Carcinoma-A Focus on Epithelial-to-Mesenchymal Transition, Autophagy, and Apoptosis

Chemoresistance has been found in all malignant tumors including colorectal carcinoma (CRC). Nowadays chemoresistance is understood as a major reason for therapy failure, with consequent tumor growth and spreading leading ultimately to the patient's premature death. The chemotherapy-related resistance of malignant colonocytes may be manifested in diverse mechanisms that may exist both prior to the onset of the therapy or after it. The ultimate function of this chemoresistance is to ensure the survival of malignant cells through continuing adaptation within an organism, therefore, the nature and spectrum of cell-survival strategies in CRC represent a highly significant target of scientific inquiry. Among these survival strategies employed by CRC cells, three unique but significantly linked phenomena stand out-epithelial-to-mesenchymal transition (EMT), autophagy, and cell death. In this mini-review, current knowledge concerning all three mechanisms including their emergence, timeline, regulation, and mutual relationships will be presented and discussed.

Chemotherapy Resistance Explained through Endoplasmic Reticulum Stress-Dependent Signaling

Cancers cells have the ability to develop chemotherapy resistance, which is a persistent problem during cancer treatment. Chemotherapy resistance develops through different molecular mechanisms, which lead to modification of the cancer cells signals needed for cellular proliferation or for stimulating an immune response. The endoplasmic reticulum (ER) is an important organelle involved in protein quality control, by promoting the correct folding of protein and ER-mediated degradation of unfolded or misfolded protein, namely, ER-associated degradation. Disturbances of the normal ER functions causes an accumulation of unfolded or misfolded proteins in the ER lumen, resulting in a condition called “ER stress (ERS).” ERS triggers the unfolded protein response (UPR)—also called the ERS response (ERSR)—to restore homeostasis or activate cell death. Although the ERSR is one emerging potential target for chemotherapeutics to treat cancer, it is also critical for chemotherapeutics resistance, as well. However, the detailed molecular mechanism of the relationship between the ERSR and tumor survival or drug resistance remains to be fully understood. In this review, we aim to describe the most vital molecular mechanism of the relationship between the ERSR and chemotherapy resistance. Moreover, the review also discusses the molecular mechanism of ER stress-mediated apoptosis on cancer treatments.

Deciphering the Mechanism of Action Involved in Enhanced Suicide Gene Colon Cancer Cell Killer Effect Mediated by Gef and Apoptin

Despite the great advances in cancer treatment, colorectal cancer has emerged as the second highest cause of death from cancer worldwide. For this type of tumor, the use of suicide gene therapy could represent a novel therapy. We recently demonstrated that co-expression of gef and apoptin dramatically inhibits proliferation of the DLD-1 colon cell line. In the present manuscript, we try to establish the mechanism underlying the enhanced induction of apoptosis by triggering both gef and apoptin expression in colon tumor cells. Scanning microscopy reveals that simultaneous expression of gef and apoptin induces the apparition of many "pores" in the cytoplasmic membrane not detected in control cell lines. The formation of pores induced by the gef gene and accentuated by apoptin results in cell death by necrosis. Moreover, we observed the presence of apoptotic cells. Performing protein expression analysis using western blot, we revealed an activation of mitochondrial apoptosis (increased expression of Pp53, cytochrome c, Bax, and caspase 9) and also the involvement of the extrinsic pathway through caspase 8activation. In conclusion, in this manuscript we demonstrate for the first time that the extrinsic pathway of apoptosis and pore formation is also involved in the cell death caused by the co-expression of the gef and apoptin genes. Our results suggest that co-expression of gef and apoptin genes induces an increase in post-apoptotic necrotic cell death and could be a valuable tool in the design of new antitumor strategies focused on the enhancement of the immune response against cancer cell death.

Bufalin induces apoptosis via mitochondrial ROS-mediated caspase-3 activation in HCT-116 and SW620 human colon cancer cells

OBJECTIVE

Bufalin has been reported to kill various types of cancer including human colorectal cancer. Our previous study demonstrated that bufalin induced cell death via autophagy in HT-29 and Caco-2 colon cancer cells, but the action of bufalin remains unclear. This study was conducted to investigate the role of bufalin in other colon cancer HCT-116 and SW620 cells as well as its potential mechanism.

METHODS

The effect of bufalin in HCT-116 and SW620 colon cancer cells was detected by assessing cell viability and cell death. Apoptotic cells were analyzed by Western blot and trypan blue dye exclusion assay. Mitochondrial ROS production was analyzed by flow cytometry after DCFDA and DHR-123 staining. The potential mechanism was investigated via pharmacological inhibitors.

RESULTS

Bufalin had high potency against HCT-116 and SW620 cells with IC50 values of 12.823 ± 1.792 nM and 26.303 ± 2.498 nM in HCT-116 and SW620 cells, respectively. Bufalin decreased cell viability, increased cell death as well as caspase-3 downstream target (cleaved PARP) accumulation, and these actions were significantly blocked by pan-caspase inhibitor zVAD-FMK. Mechanistically, ROS production, but neither the NAD(P)H oxidase, AMPK, ERK nor p38, is responsible for bufalin-induced apoptotic cell death. Moreover, bufalin-induced ROS generation is derived from mitochondria.

CONCLUSION

Bufalin significantly induces apoptosis in HCT-116 and SW620 colon cancer cells via mitochondrial ROS-mediated caspase-3 activation. We believe that our novel findings will greatly alter our current understanding on the anti-cancer mechanism of bufalin in colon cancer cells and will pave the way for further exploiting the clinical application.

Inhibition of MALAT1 reduces tumor growth and metastasis and promotes drug sensitivity in colorectal cancer

Human metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) is a long non-coding RNA known to be highly expressed in several tumors. In colorectal cancer (CRC), MALAT1 promotes cell proliferation, metastasis, and invasion in vitro and in vivo. This study aimed to investigate the effect of MALAT1 on the proliferation, migration, and drug sensitivity of CRC cells in vitro and in vivo and the mechanisms involved therein. We observed increased expression of MALAT1 in six CRC cell lines compared to that in normal cells, suggesting its involvement in CRC progression. Downregulation of MALAT1 inhibited cell migration and induced apoptosis in vitro and inhibited tumor growth and metastasis in nude mice. Furthermore, MALAT1 silencing downregulated the expression of ATP-binding cassette transporters (ABC), breast cancer resistance protein (BCRP), and multi-drug resistance proteins including MDR1 and MRP1, resulting in decreased resistance of cancer cells to 5-FU. In addition, the metastasis and invasion of HCT-116 and HCT-116/5-FU cells were regulated via targeting miR-20b-5p. Based on these observations, we infer that inhibition of MALAT1 suppressed CRC progression and metastasis and improved the sensitivity of cancer cells to 5-FU. The present study proposes a new direction to investigate the molecular mechanisms underlying the invasion and metastasis of CRC, whereby the interaction between MALAT1 and miR-20b-5p could be a novel therapeutic target for CRC.

Morin-dependent inhibition of low molecular weight protein tyrosine phosphatase (LMW-PTP) restores sensitivity to apoptosis during colon carcinogenesis: Studies in vitro and in vivo, in an Apc-driven model of colon cancer

LMW-PTP has been associated with the development of colorectal cancer (CRC) and with the resistance to chemotherapy in cancer cells. To clarify its role in vivo, we studied LMW-PTP expression in Pirc rats (F344/NTac-Apc ^am1137 ), genetically prone to CRC and resistant to apoptosis. In the morphologically normal mucosa (NM) of Pirc rats, a dramatic over-expression of LMW-PTP was found compared to wt rats (about 60 times higher). Moreover, LMW-PTP levels further increase in spontaneously developed Pirc colon tumors. To understand if and how LMW-PTP affects resistance to apoptosis, we studied CRC cell lines, sensitive (HT29 and HCT-116), or resistant (HT29R, HCT116R) to 5-Fluorouracil (5-FU): resistant cells over-express LMW-PTP. When resistant cells were challenged with morin, a polyphenol inhibiting LMW-PTP, a fast and dose-related down-regulation of LMW-PTP was observed. 5-FU and morin co-treatment dramatically decreased cell viability, increased apoptosis, and significantly impaired self-renewal ability of all the cancer cell lines we have studied. Similarly, we observed that, in Pirc rats, one-week morin administration (50 mg/kg) down-regulated LMW-PTP and restored the apoptotic response to 5-FU in the NM. Finally, administration of morin for a longer period led to a significant reduction in colon precancerous lesions, together with a down-regulation of LMW-PTP. Taken together, these results document the involvement of LMW-PTP in the process of CRC in vitro and in vivo. Morin treatment may be envisaged as a system to increase the sensitivity to chemotherapy and to prevent carcinogenesis.

Ornithine aminotransferase promoted the proliferation and metastasis of non-small cell lung cancer via upregulation of miR-21

The incidence and mortality of lung cancer ranked the first among all types of cancer in China, and non-small cell lung cancer (NSCLC) is the most common type of lung cancer accounting for 85% of all lung cancers. Given that the survival rate of patients with advanced NSCLC is still poor nowadays, identification of novel therapeutic targets and the development of effective therapies are desired for the treatment of NSCLC in clinics. In this study, we reported the upregulation of ornithine aminotransferase (OAT) in NSCLC cells and clinical tumor samples as well as its association with the advanced TNM stage, metastasis, and poor tumor differentiation of lung cancer. Using different NSCLC cell lines, we demonstrated that OAT promoted the proliferation, invasion, and migration, inhibited the apoptosis, and altered cell cycle of NSCLC cells; besides, the involvement of OAT-miR-21-glycogen synthase kinase-3β signaling in the functional role of OAT in NSCLC was also revealed. Importantly, in the absence of OAT, the growth and metastasis of tumor lung cancer xenograft was significantly suppressed in the nude mice. Based on our findings, OAT may be a potential novel biomarker for the diagnosis and therapeutic outcome monitoring of NSCLC. Inhibition of OAT may also represent a new therapeutic strategy of NSCLC.

Potentiation of the anticancer effect of doxorubicinin drug-resistant gastric cancer cells by tanshinone IIA

BACKGROUND

Gastric cancer is the fifth commonest cancer and the third cause of cancer-related deaths all over the world. The effectiveness of chemotherapy is still limited by drug resistance in gastric cancer. Tanshinones, abietane diterpenes isolated from the traditional Chinese medicine Danshen (Salvia miltiorrhiza), have exhibited versatile anticancer activities in particular the ability to overcome drug resistance in different cancers.

PURPOSE

The current study aimed to explore the capacity of tanshinone IIA, the most abundant tanshinone found in the plant Danshen, to overcome drug resistance of gastric cancer cells to a commonly used anticancer drug doxorubicin.

STUDY DESIGN

Sensitivity of cell lines to doxorubicin was determined by MTT assay. Doxorubicin resistant gastric cancer cell lines was established by step selection with increasing concentrations of doxorubicin. Cell cycle arrest, apoptosis and doxorubicin efflux were analyzed by flow cytometry. The expression of MRP1 was determined by realtime PCR and western-blot.

RESULTS

Based on the IC₅₀ values of doxorubicin, we identified the doxorubicin-sensitive gastric cancer cell lines SNU-719 and SNU-610 as well as the cell lines relatively resistant to doxorubicin including SNU-638, SNU-668, SNU-216 and SNU-620. We also established two drug-resistant cell lines SNU-719R and SNU-610R. Despite the fact that tanshinone IIA alone showed no cytotoxicity on these gastric cells, we found the potentiation of the anticancer effect of doxorubicin in drug-resistant gastric cancer cells by tanshinone IIA. Furthermore, using doxorubicin-sensitive cell line SNU-719 and doxorubicin-resistant cell lines SNU-719R and SNU-620, we revealed the pivotal roles of MRP1. Its overexpression impaired cell cycle arrest and suppressed apoptosis in the development of both intrinsic and acquired drug resistance in gastric cancer cells to doxorubicin. Importantly, inhibition of MRP1 function enhanced cell cycle arrest, increased apoptosis and induced autophagic cell death which contributed to the capability of tanshinone IIA to potentiate the anticancer effect of doxorubicin in drug-resistant gastric cancer cells.

CONCLUSION

Tanshinone IIA is an interesting agent with potential to treat drug-resistant gastric cancer in combination therapy.

P-glycoprotein-targeted photodynamic therapy boosts cancer nanomedicine by priming tumor microenvironment

Cancer nanomedicines only modestly improve the overall survival of patients because their anticancer activity is limited by biological barriers posed by the tumor microenvironment. Currently, all the drugs in FDA-approved cancer nanomedicines are substrates for P-glycoprotein (Pgp), and thus, Pgp-mediated multidrug resistance (MDR) remains a hurdle for cancer nanomedicines.

Methods: In this study, Pgp-targeted photodynamic therapy (PDT) was developed to enhance the anticancer efficacy of nanomedicines by depleting MDR cancer cells as well as enhancing tumor penetration of nanomedicines. We first examined the Pgp specificity of our targeted PDT approach, and then tested combination therapy of PDT with Doxil in mixed tumor models of MDR cancer cells and stromal cells, mimicking human heterogeneous tumors.

Results: In vitro studies showed that the antibody-photosensitizer conjugates produced Pgp-specific cytotoxicity towards MDR cancer cells upon irradiation with a near-infrared light. The studies with a co-culture model of MDR cancer cells and stromal cells revealed synergistic effects in the combination therapy of PDT with Doxil. Using a mouse model of mixed tumors containing MDR cancer cells and stroma cells, we observed markedly enhanced tumor delivery of Doxil after PDT in vivo. We further examined the effects of the two modalities on individual cell populations and their synergism using an in vivo dual substrate bioluminescence assay. The results indicated that Pgp-targeted PDT specifically depleted MDR cancer cells and further enhanced Doxil's actions on both MDR cancer cells and stromal cells.

Conclusion: We conclude that our targeted PDT approach markedly enhances anticancer actions of nanomedicines by depleting MDR cancer cells and increasing their tumor penetration, and thereby, may provide an effective approach to facilitate translation of cancer nanomedicines.

Combination Therapy with EpCAM-CAR-NK-92 Cells and Regorafenib against Human Colorectal Cancer Models

Adoptive chimeric antigen receptor-modified T or NK cells (CAR-T or CAR-NK) offer new options for cancer treatment. CAR-T therapy has achieved encouraging breakthroughs in the treatment of hematological malignancies. However, their therapeutic efficacy against solid tumors is limited. New regimens, including combinations with chemical drugs, need to be studied to enhance the therapeutic efficacy of CAR-T or NK cells for solid tumors. An epithelial cell adhesion molecule- (EpCAM-) specific second-generation CAR was constructed and transduced into NK-92 cells by lentiviral vectors. Immune effects, including cytokine release and cytotoxicity of the CAR-NK-92 cells against EpCAM-positive colon cancer cells, were evaluated in vitro. Synergistic effects of regorafenib and CAR-NK-92 cells were analyzed in a mouse model with human colorectal cancer xenografts. The CAR-NK-92 cells can specifically recognize EpCAM-positive colorectal cancer cells and release cytokines, including IFN-γ, perforin, and granzyme B, and show specific cytotoxicity in vitro. The growth suppression efficacy of combination therapy with regorafenib and CAR-NK-92 cells on established EpCAM-positive tumor xenografts was more significant than that of monotherapy with CAR-NK-92 cells or regorafenib. Our results provided a novel strategy to treat colorectal cancer and enhance the therapeutic efficacy of CAR-modified immune effector cells for solid tumors.

Olmutinib (BI1482694/HM61713), a Novel Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitor, Reverses ABCG2-Mediated Multidrug Resistance in Cancer Cells

The main characteristic of tumor cell resistance is multidrug resistance (MDR). MDR is the principle cause of the decline in clinical efficacy of chemotherapeutic drugs. There are several mechanisms that could cause MDR. Among these, one of the most important mechanisms underlying MDR is the overexpression of adenosine triphosphate (ATP)-binding cassette (ABC) super-family of transporters, which effectively pump out cytotoxic agents and targeted anticancer drugs across the cell membrane. In recent years, studies found that ABC transporters and tyrosine kinase inhibitors (TKIs) interact with each other. TKIs may behave as substrates or inhibitors depending on the expression of specific pumps, drug concentration, their affinity for the transporters and types of co-administered agents. Therefore, we performed in vitro experiments to observe whether olmutinib could reverse MDR in cancer cells overexpressing ABCB1, ABCG2, or ABCC1 transporters. The results showed that olmutinib at 3 μM significantly reversed drug resistance mediated by ABCG2, but not by ABCB1 and ABCC1, by antagonizing the drug efflux function in ABCG2-overexpressing cells. In addition, olmutinib at reversal concentration affected neither the protein expression level nor the localization of ABCG2. The results observed from the accumulation/efflux study of olmutinib showed that olmutinib reversed ABCG2-mediated MDR with an increasing intracellular drug accumulation due to inhibited drug efflux. We also had consistent results with the ATPase assay that olmutinib stimulated ATPase activity of ABCG2 up to 3.5-fold. Additionally, the molecular interaction between olmutinib and ABCG2 was identified by docking simulation. Olmutinib not only interacts directly with ABCG2 but also works as a competitive inhibitor of the transport protein. In conclusion, olmutinib could reverse ABCG2-mediated MDR. The reversal effect of olmutinib on ABCG2-mediated MDR cells is not due to ABCG2 expression or intracellular localization, but rather related to its interaction with ABCG2 protein resulting in drug efflux inhibition and ATPase stimulation.

Triticum aestivum Sprouts Extract Inhibits Azoymethane (AOM)/Dextran Sodium Sulfate (DSS)-Induced Colon Carcinogenesis in Mice

Chronic intestinal inflammation is critical risk factor of colorectal cancer. Triticum aestivum sprouts have been reported to provide a number of health benefits and used as a dietary supplement. In this study, the authors investigated the regulatory effects of T. aestivum sprouts ethanol extract (TAEE) on experimental colorectal carcinogenesis in an azoxymethane (AOM)/dextran sulfate sodium (DSS)-induced mouse model. Oral administration of TAEE significantly attenuated crypt destruction and tumor formation in AOM/DSS-treated mice. Levels of inflammatory mediators involved in colorectal carcinogenesis, that is, tumor necrosis factor-α, interkeukin (IL)-1β, IL-6, cyclooxygenase-2, and inducible nitric oxide synthase, were lower in the colons of 200 mg/kg TAEE-treated mice than in AOM/DSS controls (p < 0.05). Immunohistochemical staining showed that levels of nuclear factor-kappa B p65 and β-catenin were attenuated by TAEE in the colon tissues of AOM/DSS-treated mice. Furthermore, levels of β-catenin-related genes (cyclin D1 and c-Myc), which are known to contribute to cell cycle regulation, were decreased in the colon tissues of TAEE-treated mice versus AOM/DSS controls (p < 0.01). These results showed TAEE inhibited colon inflammation and neoplasm formation caused by AOM/DSS treatment, suggesting that TAEE could be useful for the prevention and treatment of colitis-associated colon cancer.

Cullin-1 and -2 Protein Expression in Colorectal Cancer: Correlation with Clinicopathological Variables

BACKGROUND/AIM

The cullin (CUL) family of proteins is involved in the ubiquitin/mediated degradation of proteins, regulating cell proliferation, cell-cycle control, migration, invasion and metastasis in the process of tumor progression. The aim of the present study was to examine if there is any correlation between the immunohistochemical (IHC) expression of Cullin-1 and -2 proteins in colorectal cancer tissue specimens with several clinicopathological variables.

MATERIALS AND METHODS

Between January 2012 and December 2014, 96 consecutive adenocarcinoma patients were submitted to oncological colectomy, as the first therapeutic option, with a curative intent. CUL-1 and -2 protein expression was examined with IHC on paraffin-embedded tissue sections. CUL-1 and -2 protein positivity, was correlated with patients' age, gender, stage, histological grade, proliferative capacity (Ki-67 labeling index) and mutant p53 protein expression. The positivity for CUL-1, CUL-2, mutant p53 protein and Ki-67 index, was determined by the percentage of their IHC expression in the total number of cancer cells.

RESULTS

Choosing as a cut-off point for CUL-1 positivity the 10%, a statistically significant relationship of the expression of the mutant p53 protein (p=0.04) and the co-expression of CUL-2 (p=0.003) were noticed. By setting the cut-off limit for CUL-2 expression to 10%, no statistically significant differences were observed between its expression and the examined clinicopathological variables. However, by increasing the cut-off limit for CUL-2 expression to 30%, a statistically significant correlation of its expression to the mutated p53 protein was noticed (p=0.047). Co-expression of CUL-1 and -2 in more than 10%, significantly correlated to the coexistence of adenomatous polyps along the large bowel (p=0.0329). Multivariate analysis of CUL-1 and -2 co-expression in more than 10% disclosed their expression as an independent factor for adenomatous polyps development in the large bowel (p=0.035, RR=2.1).

CONCLUSION

CUL-1 overexpression may happen early in the process of carcinogenesis mainly affecting the vulnerable p53(+) large bowel cells, arresting them in the G1 phase of cell-cycle, while it may also induce the expression of CUL-2. Co-expression of CUL-1 and CUL-2, in the arrested (in G1 phase) large bowel cells, promotes carcinogenesis up to adenomatous polyp formation. Since no relationship between cullins expression and development of cancer on adenoma was found, the results of the present study may be useful explaining the initiation but not the progression of carcinogenesis in colorectal cancer. Further molecular and clinical studies are needed in order to delineate the clinical importance of these proteins in the management of colorectal cancer patients.

Doxorubicin resistance induces IL6 activation in the colon cancer cell line LS180

Despite improvements in the development of drugs for the treatment of cancer, drug resistance remains a major obstacle. In colon cancer, following an initially promising response, patients develop drug resistance, which impacts the efficacy and halts the response of cancerous cells towards drugs. In the present study, a phosphatase and tensin homolog (PTEN) knockdown model of LS180 cells, doxorubicin-resistant models of LS180 cells as well as doxorubicin-resistant LS180 (PTEN) knockdown model were established. The present study demonstrated that doxorubicin resistance led to the activation of interleukin (IL)6 signalling pathway which was enhanced by knockdown of PTEN. There was also an increase in the levels of IL8 and IL2 which were further enchanced by knockdown of PTEN. Doxorubicin resistance also led to an increase in the population of cancer stem cells in LS180 and shPTEN-treated LS180 cells. Notably, doxorubicin resistance also induced epithelial to mesenchymal transition and increased the formation of mammospheres. Furthermore, the present study also reported that IL6 receptor antibody not only decreased IL6 levels but also led to a significant decreased number of cancer stem cell like population and mammosphere formation. In conclusion, in the present study it was demonstrated that doxorubicin resistance led to activation of IL6 signalling pathway which was further elevated by the knockdown of PTEN in the colon cancer cell line LS180. Thus, inhibiting the IL6 loop may provide an alternative pathway to tackle doxorubicin resistance.

miRNAs and lncRNAs as Predictive Biomarkers of Response to FOLFOX Therapy in Colorectal Cancer

Chemotherapy is one of the options for cancer treatment. FOLFOX is one of the widely used chemotherapeutic regimens used to treat primarily colorectal cancer and other cancers as well. However, the emergence of chemo-resistance clones during cancer treatment has become a critical challenge in the clinical setting. It is crucial to identify the potential biomarkers and therapeutics targets which could lead to an improvement in the success rate of the proposed therapies. Since non-coding RNAs have been known to be important players in the cellular system, the interest in their functional roles has intensified. Non-coding RNAs (ncRNAs) as regulators at the post-transcriptional level could be very promising to provide insights in overcoming chemo-resistance to FOLFOX. Hence, this mini review attempts to summarize the potential of ncRNAs correlating with chemo-sensitivity/resistance to FOLFOX.

P-glycoprotein targeted and near-infrared light-guided depletion of chemoresistant tumors

Drug resistance remains a formidable challenge to cancer therapy. P-glycoprotein (Pgp) contributes to multidrug resistance in numerous cancers by preventing accumulation of anticancer drugs in cancer cells. Strategies to overcome this resistance have been vigorously sought for over 3 decades, yet clinical solutions do not exist. The main reason for the failure is lack of cancer specificity of small-molecule Pgp inhibitors, thus causing severe toxicity in normal tissues. In this study, Pgp-targeted photodynamic therapy (PDT) was developed to achieve superior cancer specificity through antibody targeting plus locoregional light activation. Thus, a Pgp monoclonal antibody was chemically modified with IR700, a porphyrin photosensitizer. In vitro studies showed that the antibody-photosensitizer conjugates specifically bind to Pgp-expressing drug resistant cancer cells, and caused dramatic cytotoxicity upon irradiation with a near infrared light. We then tested our Pgp-targeted approach in mouse xenograft models of chemoresistant ovarian cancer and head and neck cancer. In both models, targeted PDT produced rapid tumor shrinkage, and significantly prolonged survival of tumor-bearing mice. We conclude that our targeted PDT approach produces molecularly targeted and spatially selective ablation of chemoresistant tumors, and thereby provides an effective approach to overcome Pgp-mediated multidrug resistance in cancer, where conventional approaches have failed.

Comparative analysis of the bioenergetics of human adenocarcinoma Caco-2 cell line and postoperative tissue samples from colorectal cancer patients

The aim of this work was to explore the key bioenergetic properties for mitochondrial respiration in the widely-used Caco-2 cell line and in human colorectal cancer (HCC) postoperational tissue samples. Oxygraphy and metabolic control analysis (MCA) were applied to estimate the function of oxidative phosphorylation in cultured Caco-2 cells and HCC tissue samples. The mitochondria of Caco-2 cells and HCC tissues displayed larger functional activity of respiratory complex (C)II compared with CI, whereas in normal colon tissue an inverse pattern in the ratio of CI to CII activity was observed. MCA showed that the respiration in Caco-2 and HCC tissue cells is regulated by different parts of electron transport chain. In HCC tissues, this control is performed essentially at the level of respiratory chain complexes I-IV, whereas in Caco-2 cells at the level of CIV (cytochrome c oxidase) and the ATP synthasome. The differences we found in the regulation of respiratory chain activity and glycose index could represent an adaptive response to distinct growth conditions; this highlights the importance of proper validation of results obtained from in-vitro models before their extrapolation to the more complex in-vivo systems.

miR-329 regulates the sensitivity of 5-FU in chemotherapy of colorectal cancer by targeting E2F1

Colorectal cancer (CRC) is a common digestive system malignancy with high morbidity and mortality. Accumulating studies have shown that miRNAs play a critical role in the progression of CRC. Here, we explored the effect of miR-329 and its target gene on the sensitivity of 5-fluorouracil (5-FU) in the chemotherapy of CRC. RT-qPCR was utilized to determine the expression of miR-329 in cancer tissues, adjacent tissues and cells. CCK-8 and Transwell assays were introduced to detect the role of miR-329 overexpression in cell viability and invasion. Luciferase reporter assay was performed to verify that E2F1 was a direct target of miR-329. Protein expression of E2F1 was accessed by western blot analysis. The expression level of miR-329 was decreased in CRC tissues and tumor tissues at stage III+IV with lymph node metastasis, and the patients' total survival time was positively associated with the expression of miR-329. Overexpression of miR-329 significantly attenuated the viability and invasiveness of tumor cells. The viability of drug-resistant cells was markedly higher than that of non-resistant cells under the same dose of 5-FU treatment. The expression of miR-329 in tumor cells was negatively associated with drug sensitivity. Luciferase reporter assay showed that E2F1 was the direct target of miR-329. Besides, the expression of E2F1 protein in drug-resistant cells was remarkably higher than that in the non-resistant cells, while the overexpression of miR-329 significantly decreased the expression of E2F1 protein. E2F1 overexpression increased cell viability, but overexpression of both E2F1 and miR-329 in turn decreased cell viability. miR-329 expression is reduced in CRC, and overexpression of miR-329 promotes the sensitivity of 5-FU in the chemotherapy of CRC by degrading the target gene E2F1.

A Systems-Level Analysis Reveals Circadian Regulation of Splicing in Colorectal Cancer

Accumulating evidence points to a significant role of the circadian clock in the regulation of splicing in various organisms, including mammals. Both dysregulated circadian rhythms and aberrant pre-mRNA splicing are frequently implicated in human disease, in particular in cancer. To investigate the role of the circadian clock in the regulation of splicing in a cancer progression context at the systems-level, we conducted a genome-wide analysis and compared the rhythmic transcriptional profiles of colon carcinoma cell lines SW480 and SW620, derived from primary and metastatic sites of the same patient, respectively. We identified spliceosome components and splicing factors with cell-specific circadian expression patterns including SRSF1, HNRNPLL, ESRP1, and RBM 8A, as well as altered alternative splicing events and circadian alternative splicing patterns of output genes (e.g., VEGFA, NCAM1, FGFR2, CD44) in our cellular model. Our data reveals a remarkable interplay between the circadian clock and pre-mRNA splicing with putative consequences in tumor progression and metastasis.

Development of an Efficient Dual-Action GST-Inhibiting Anticancer Platinum(IV) Prodrug

The cytotoxicity of cisplatin (cDDP) is enhanced when co-administered with ethacrynic acid (EA), a glutathione S-transferase (GST) inhibitor. A Pt^IV -EA conjugate containing a cDDP core and two axial ethacrynate ligands (compound 1) was shown to be an excellent inhibitor of GST, but did not readily release a Pt^II species to exert a synergistic cytotoxic effect. In this study, a redesigned Pt^IV construct composed of a cDDP core with one axial ethacrynate ligand and one axial hydroxido ligand (compound 2) was prepared and shown to overcome the limitations of compound 1. The EA ligand in 2 is readily released in vitro together with a cytotoxic Pt^II species derived from cisplatin, working together to inhibit cell proliferation in cDDP-resistant human ovarian cancer cells. The in vitro activity translates well in vivo with 2, showing effective (∼80 %) inhibition of tumor growth in a human ovarian carcinoma A2780 tumor model, while showing considerably lower toxicity than cisplatin, thus validating the new design strategy.

Wnt6 contributes tumorigenesis and development of colon cancer via its effects on cell proliferation, apoptosis, cell-cycle and migration

Wnt proteins have been reported to contribute to the progression of various types of cancer. Wnt6 is a member of the Wnt family and may promote tumorigenesis in gastrointestinal cancer and cervical cancer. In the present study, the expression of Wnt6 in human colon cancer cell lines was evaluated, in order to investigate the role of Wnt6 in the development of colon cancer. Additionally, the effects of Wnt6 upregulation or downregulation on proliferation, apoptosis, cell cycle and cell migration of colon cancer cells have been investigated. Furthermore, western blot analysis was employed to evaluate the expression of Wnt6, B-cell lymphoma 2-associated X protein (Bax), caspase-3 and matrix metalloproteinase (MMP)2. The results of the present study demonstrated that the expression of Wnt6 was increased in HCT116 and SW480 cells compared with the remaining colon cancer cell lines. Furthermore, overexpression Wnt6 resulting from transfection of pGPU6/GFP/Neo-Wnt6-Homo-1 plasmid promoted the proliferation, cell cycle and migration of HCT116 and SW480 cells, but inhibited cell apoptosis in vitro. The expression of caspase-3 and MMP2 was increased, whereas the expression of Bax was decreased in response to upregulation of Wnt6. These results suggested that Wnt6 may serve a vital function in the development of colon cancer.

Autophagy and doxorubicin resistance in cancer

Doxorubicin (DOX), also known as adriamycin, is a DNA topoisomerase II inhibitor and belongs to the family of anthracycline anticancer drugs. DOX is used for the treatment of a wide variety of cancer types. However, resistance among cancer cells has emerged as a major barrier to effective treatment using DOX. Currently, the role of autophagy in cancer resistance to DOX and the mechanisms involved have become one of the areas of intense investigation. More and more preclinical data are being obtained on reversing DOX resistance through modulation of autophagy as one of the promising therapeutic strategies. This review summarizes the recent advances in autophagy-targeting therapies that overcome DOX resistance from in-vitro studies to animal models for exploration of novel delivery systems. In-depth understanding of the mechanisms of autophagy regulation in relation to DOX resistance and development of molecularly targeted autophagy-modulating agents will provide a promising therapeutic strategy for overcoming DOX resistance in cancer treatment.

Metformin increases the cytotoxicity of oxaliplatin in human DLD-1 colorectal cancer cells through down-regulating HMGB1 expression

Colorectal cancer (CRC) is the fourth most common cause of cancer death worldwide. Chemotherapy has been the major strategy for treating patients with advanced CRC. Oxaliplatin (OXA) is used as both an adjuvant and neoadjuvant anticancer agent available to treat advanced CRC. High-mobility group box 1 protein (HMGB1) is a critical regulator of cell death and survival. HMGB1 overexpression has been shown to be resistant to cytotoxic agents. In addition, Metformin, a widely used drug for diabetes, has emerged as a potential anticancer agent. In this study, we examined whether HMGB1 plays a role in the OXA- and/or metformin-induced cytotoxic effect on CRC cells. The results showed that treatment with OXA increased HMGB1 expression in the ERK1/2- and Akt-dependent manners in DLD-1 cells. HMGB1 gene knockdown enhanced the cytotoxicity and cell growth inhibition of OXA. Moreover, OXA-increased HMGB1 expression was by inducing NF-κB-DNA-binding activity to in DLD-1 cells. Compared to a single agent, OXA combined with metformin administration resulted in cytotoxicity and cell growth inhibition synergistically, accompanied with reduced HMGB1 level. These findings may have implications for the rational design of future drug regimens incorporating OXA and metformin for the treatment of CRC.

PMN inhibits colorectal cancer cells through inducing mitotic arrest and p53-dependent apoptosis via the inhibition of tubulin polymerization

Colorectal cancer (CRC) is the third most prevalent malignancy worldwide. New understandings about this disease are urgently required to guide clinical therapies. In this study, we focused on the effects of the small molecule PMN on CRC cells. PMN dose-dependently inhibited CRC cell proliferation through inducing mitotic arrest and apoptosis. PMN induced mitotic arrest via the disruption of spindle apparatus by inhibiting microtubule polymerization. PMN-induced mitotic arrest resulted in apoptosis and p53 upregulation. Furthermore, p53 upregulation sensitized PMN-induced mitotic cells to apoptosis. This study deepens the understanding of the effects of p53 on the response of CRC cells to PMN, providing the basis for the potential development of PMN as a lead compound of microtubule-destabilizers for p53-positive CRC treatment.

A novel 5T4-targeting antibody-drug conjugate H6-DM4 exhibits potent therapeutic efficacy in gastrointestinal tumor xenograft models

5T4, also named as trophoblast glycoprotein, is often upregulated in some cancer cells. Here, we demonstrated that 5T4 was highly expressed in gastric, colorectal, and pancreatic cancer, associated with significantly poor prognosis of gastrointestinal (GI) cancer patients. To search for new targeting drugs for GI cancer, we developed a novel anti-5T4 monoclonal antibody with high affinity and robust internalization ability and conjugated it to the potent microtubule inhibitor DM4 to produce conjugate H6-DM4. This antibody-drug conjugate (ADC) displayed significant cytotoxicity in a panel of GI cancer cell lines with IC50 values in the nanomolar range. H6-DM4 eradicated established GI tumor xenograft models at 2.5 mg/kg or 10 mg/kg without observable toxicity. Further, 5T4 was highly expressed in cancer-initiating cells (CICs) compared with non-CICs in colorectal cancer. In vitro and in vivo, treatment with H6-DM4 exhibited a powerful efficacy on colorectal CICs. Additionally, colorectal cancer cells resistant to platinum were effectively eliminated by H6-DM4. Taken together, our results showed 5T4-positive GI cancer cells, colorectal cancer-initiating cells, and platinum-resistant colorectal cancer cells were potently eliminated by H6-DM4, indicating H6-DM4 may be a potential candidate drug for GI cancer treatment.

Drug resistance related to aberrant glycosylation in colorectal cancer

Colorectal cancer (CRC) is the fourth leading cause of cancer-related deaths in the world. Drug resistance of tumour cells remains the main challenge toward curative treatments efficiency. Several epidemiologic studies link emergence and recurrence of this cancer to metabolic disorders. Glycosylation that modifies more than 80% of human proteins is one of the most widepread nutrient-sensitive post-translational modifications. Aberrant glycosylation participates in the development and progression of cancer. Thus, some of these glycan changes like carbohydrate antigen CA 19-9 (sialyl Lewis a, sLea) or those found on carcinoembryonic antigen (CEA) are already used as clinical biomarkers to detect and monitor CRC. The current review highlights emerging evidences accumulated mainly during the last decade that establish the role played by altered glycosylations in CRC drug resistance mechanisms that induce resistance to apoptosis and activation of signaling pathways, alter drug absorption and metabolism, and led to stemness acquisition. Knowledge in this field of investigation could aid to the development of better therapeutic approaches with new predictive biomarkers and targets tied in with adapted diet.

Upregulated solute carrier family 37 member 1 in colorectal cancer is associated with poor patient outcome and metastasis

Solute carrier (SLC) drug transporters exchange various molecules without energy from adenosine triphosphate hydrolysis, indicating an association with anticancer drug resistance. However, the expression and role of SLC transporters in malignant tumors has not yet been fully elucidated. Therefore, in the current study, the expression of SLC37A family genes was evaluated in patients with colorectal cancer (CRC), and it was revealed that SLC family 37 member 1 (SLC37A1) expression was significantly increased in tumorous tissues compared with that in non-tumorous tissues. The cases with upregulated expression of SLC37A1 by immunohistochemical staining were significantly associated with positive venous invasion and liver metastasis. Furthermore, upregulated SLC37A1 expression was associated with poor overall survival time in the present cohort. These results indicated that SLC37A1 is involved in the hematogenous metastasis of CRC. To investigate whether SLC37A1 is associated with hematogenous metastasis and glycolipid metabolism, SLC37A1 was knocked down in colon cancer cells, and the expression of sialyl Lewis A and sialyl Lewis X was observed to be decreased. In summary, upregulation of SLC37A1 was observed in patients with CRC, and was associated with poor patient outcomes and survival. To the best of our knowledge, the present study is the first to propose a key role of SLC37A1 in CRC, and additional studies are warranted to reveal the functional role of SLC37A1 in CRC development.

GOLPH3 expression promotes the resistance of HT29 cells to 5‑fluorouracil by activating multiple signaling pathways

The novel proto‑oncogene Golgi phosphoprotein (GOLPH)3 is overexpressed in a variety of tumor tissues and is associated with poor prognosis. The authors previously demonstrated that GOLPH3 gene is overexpressed in colorectal cancer tissues and promotes the proliferation of colonic cancer cells by activating the phosphatidylinositol‑3‑kinase/protein kinase B/the mammalian target of rapamycin and Wnt/β‑catenin signaling pathways. However, to the best of the authors' knowledge, if and how the GOLPH3 gene is involved in inducing resistance to colonic cancer chemotherapy has not been reported. In the present study, the association between the overexpression of the GOLPH3 gene and resistance of HT29 colonic cancer cells to 5‑fluorouracil (5‑FU) was investigated. Following confirmation of the effective silencing of the GOLPH3 gene, proliferation and apoptosis of colonic cancer cells were detected by MTT assay, colony formation assay and flow cytometry, and then the mechanism of GOLPH3‑induced resistance to 5‑FU chemotherapy in colonic cancer cells was investigated by western blotting. The results demonstrated that the expression of phosphorylated (p)‑glycoprotein and GOLPH3 was increased in HT29 cells following treatment with 5‑FU, which resulted in the development of drug resistance. Silencing GOLPH3 increased the sensitivity of HT29 cells to 5‑FU, reduced their tumorigenicity and partly reversed their resistance to 5‑FU. The expression of p‑extracellular signal‑regulated kinase (pERK)1/2 and β‑catenin was decreased, which indicated that its mechanism was associated with the activation of the mitogen‑activated protein kinase/ERK and Wnt/β‑catenin signaling pathways. Therefore, GOLPH3 may be a potential, novel target for reversing chemotherapy resistance in colon cancer.

Glycyrrhizic acid: A promising carrier material for anticancer therapy

Drug delivery systems have become an integral part of anticancer drugs today. Design of novel drug carriers may lead to significant enhancement in antineoplastic therapy. Glycyrrhizic acid (GL), which is the most important active ingredient extracted from the licorice root shows great potential as a carrier material in this field. Recent studies have indicated that the combination of GL and first-line drugs had better therapeutic effects on cancers. GL showed a series of anti-cancer-related pharmacological activities, such as broad-spectrum anti-cancer ability, resistance to the tissue toxicity caused by chemotherapy and radiation, drug absorption enhancing effects and anti-multidrug resistance (MDR) mechanisms, as a carrier material in drug delivery systems. This review introduced the current research progress on pharmacological mechanisms of GL and development of GL-based drug carriers in anti-cancer field to provide basis for the application prospects of GL. The design of novel GL-based drug delivery systems will bring new opportunities and challenges to anti-cancer therapy.

Microscale Mass Spectrometry Analysis of Extracellular Metabolites in Live Multicellular Tumor Spheroids

Extracellular compounds in tumors play critical roles in intercellular communication, tumor proliferation, and cancer cell metastasis. However, the lack of appropriate techniques leads to limited studies of extracellular metabolite. Here, we introduced a microscale collection device, the Micro-funnel, fabricated from biocompatible fused silica capillary. With a small probe size (∼25 μm), the Micro-funnel can be implanted into live multicellular tumor spheroids to accumulate the extracellular metabolites produced by cancer cells. Metabolites collected in the Micro-funnel device were then extracted by a microscale sampling and ionization device, the Single-probe, for real-time mass spectrometry (MS) analysis. We successfully detected the abundance change of anticancer drug irinotecan and its metabolites inside spheroids treated under a series of conditions. Moreover, we found that irinotecan treatment dramatically altered the composition of extracellular compounds. Specifically, we observed the increased abundances of a large number of lipids, which are potentially related to the drug resistance of cancer cells. This study provides a novel way to detect the extracellular compounds inside live spheroids, and the successful development of our technique can benefit the research in multiple areas, including the microenvironment inside live tissues, cell-cell communication, biomarker discovery, and drug development.

Apatinib has anti-tumor effects and induces autophagy in colon cancer cells

OBJECTIVES

Apatinib recently has been used to treat patients with gastric cancer, but the function of apatinib in colon cancer remains unclear. This study was conducted to investigate the impacts of apatinib on the biological function and its potential mechanism of colon cancer cells in vitro.

MATERIALS AND METHODS

The effect of apatinib in colon cancer cells were detected by assessing cell viability, migration and invasion capabilities. Apoptosis cells and the cell cycle distribution of colon cancer cells were analyzed by flow cytometry. The potential mechanism was investigated via autophagy related proteins and pathways in vitro.

RESULTS

The proliferation, migration and invasion of colon cancer cells were inhibited when they were treated with different concentration of apatinib (20, 40 μM). When HCT116 and SW480 cells were treated with apatinib at the concentration of 20 μM, the apoptosis percentage were 3.7% and 5.8% respectively. As the drug concentration increased to 40μΜ, the the apoptosis percentage increased to 11.9% and 13.5%. Meanwhile, cell cycle was also altered. Furthermore, apatinib inhibited the expression of AKT-mTOR signaling pathway and increased the expression of LC3-II.

CONCLUSION

Apatinib can significantly inhibit the malignant phenotype of colon cancer cells, and it was involved in regulation of autophagy.

Epithelial-mesenchymal transition and cancer stem cell-like phenotype induced by Twist1 contribute to acquired resistance to irinotecan in colon cancer

Inherent and acquired chemoresistance reduce the effectiveness of irinotecan in the treatment of metastatic colorectal cancer (CRC). However, the molecular mechanisms underlying this resistance process are still unclear. Twist1 is one of the master transcription factors of epithelial-mesenchymal transition (EMT). Our previous study indicated that Twist1 is overexpressed in colon cancer tissues, and demonstrated that Twist1 plays a crucial role in the chemoresistance of CRC. In the present study, we further investigated how Twist1 contribute to acquired resistance to irinotecan in colon cancer. The irinotecan-resistant cells were established by gradual adaptation of increasing irinotecan concentrations in LoVo cells, named LoVo/CPT-11R cells. Results showed that cell viabilities to different anticancer drugs were markedly increased in LoVo/CPT-11R cells compared to LoVo cells. Moreover, LoVo/CPT-11R cells displayed EMT, CSC-like cellular morphology and relative biomarkers were also significantly increased. In addition, overexpressed Twist1 LoVo cells were established by lentivirus transfection assay, named LoVo/Twist1 cells. Results showed that the LoVo/Twist1 cells perform a distinctly decreased sensitivity to irinotecan, downregulated expression of E-cadherin, upregulated expression of cluster of differentiation 44 (CD44), and a significant enhancement of invasion and migration potential by regulation of MMP2 compared with control cells. In contrast, the inhibition of Twist1 transfected with siRNA could enhance the irinotecan sensitivity in LoVo/CPT-11R cells and downregulate the expression of vimentin and CD44. Our data provide evidence that EMT and CSC-like phenotype induced by Twist1 contribute to acquire resistance to irinotecan and enhanced migration and invasion in colon cancer.

Aldose reductase inhibitor increases doxorubicin-sensitivity of colon cancer cells and decreases cardiotoxicity

Anthracycline drugs such as doxorubicin (DOX) and daunorubicin remain some of the most active wide-spectrum and cost-effective drugs in cancer therapy. However, colorectal cancer (CRC) cells are inherently resistant to anthracyclines which at higher doses cause cardiotoxicity. Our recent studies indicate that aldose reductase (AR) inhibitors such as fidarestat inhibit CRC growth in vitro and in vivo. Here, we show that treatment of CRC cells with fidarestat increases the efficacy of DOX-induced death in HT-29 and SW480 cells and in nude mice xenografts. AR inhibition also results in higher intracellular accumulation of DOX and decreases the expression of drug transporter proteins MDR1, MRP1, and ABCG2. Further, fidarestat also inhibits DOX-induced increase in troponin-I and various inflammatory markers in the serum and heart and restores cardiac function in mice. These results suggest that fidarestat could be used as adjuvant therapy to enhance DOX sensitivity of CRC cells and to reduce DOX-associated cardiotoxicity.

Dual-functional drug liposomes in treatment of resistant cancers

Efficacy of regular chemotherapy is significantly hampered by multidrug resistance (MDR) and severe systemic toxicity. The reduced toxicity has been evidenced after administration of drug liposomes, consisting of the first generation of regular drug liposomes, the second generation of long-circulation drug liposomes, and the third generation of targeting drug liposomes. However, MDR of cancers remains as an unsolved issue. The objective of this article is to review the dual-functional drug liposomes, which demonstrate the potential in overcoming MDR. Herein, dual-functional drug liposomes are referring to the drug-containing phospholipid bilayer vesicles that possess a dual-function of providing the basic efficacy of drug and the extended effect of the drug carrier. They exhibit unique roles in treatment of resistant cancer via circumventing drug efflux caused by adenosine triphosphate binding cassette (ABC) transporters, eliminating cancer stem cells, destroying mitochondria, initiating apoptosis, regulating autophagy, destroying supply channels, utilizing microenvironment, and silencing genes of the resistant cancer. As the prospect of an estimation, dual-functional drug liposomes would exhibit more strength in their extended function, hence deserving further investigation for clinical validation.

Codelivery of dihydroartemisinin and doxorubicin in mannosylated liposomes for drug-resistant colon cancer therapy

Multidrug resistance (MDR) is a major hurdle in cancer chemotherapy and makes the treatment benefits unsustainable. Combination therapy is a commonly used method for overcoming MDR. In this study we investigated the anti-MDR effect of dihydroartemisinin (DHA), a derivative of artemisinin, in combination with doxorubicin (Dox) in drug-resistant human colon tumor HCT8/ADR cells. We developed a tumor-targeting codelivery system, in which the two drugs were co-encapsulated into the mannosylated liposomes (Man-liposomes). The Man-liposomes had a mean diameter of 158.8 nm and zeta potential of -15.8 mV. In the HCT8/ADR cells that overexpress the mannose receptors, the Man-liposomes altered the intracellular distribution of Dox, resulting in a high accumulation of Dox in the nuclei and thus displaying the highest cytotoxicity (IC₅₀=0.073 μg/mL) among all the groups. In a subcutaneous HCT8/ADR tumor xenograft model, administration of the Man-liposomes resulted in a tumor inhibition rate of 88.59%, compared to that of 47.46% or 70.54%, respectively, for the treatment with free Dox or free Dox+DHA. The mechanisms underlying the anti-MDR effect of the Man-liposomes involved preferential nuclear accumulation of the therapeutic agents, enhanced cancer cell apoptosis, downregulation of Bcl-xl, and the induction of autophagy.