Chemoresistant Colon Cancer Cells Research Articles

Potential Oncogenic and Immunosuppressive Roles of Multiple EGF-Like Domains 6 (MEGF6) in Colon Cancer: Insights from Bioinformatic Analysis

Multiple epidermal growth factor-like domains protein 6 (MEGF6) is a high molecular weight protein with several EGF-like domains. Although it has been demonstrated to promote metastasis and chemoresistance in colon cancer cells, its specific oncogenic and immunologic functions remain largely unexplored. This study aims to comprehensively analyze publicly available datasets to define the role of MEGF6 in colon cancer development and immune response modulation. The expression of MEGF6 in colon adenocarcinoma (COAD) and normal tissues at both mRNA and protein levels was assessed using the GEPIA2 and HPA databases, respectively. The UALCAN database was employed to examine the association between MEGF6 expression and clinicopathological outcomes in COAD patients, and survival analysis was conducted using the KM plotter database. Functional enrichment analysis of MEGF6-correlated genes was performed using the ShinyGO online tool. Additionally, the correlation of MEGF6 with immune cell infiltration and immunosuppressive molecules was explored through the TIMER and TISIDB databases. Our analysis revealed significantly higher mRNA and protein expressions of MEGF6 in COAD tissues compared to normal tissues, with associations to cancer stage, nodal metastasis status, and histological subtype. High MEGF6 expression was correlated with poorer survival outcomes, and genes correlated with MEGF6 were enriched in biological processes related to cellular component organization, cell adhesion, and extracellular matrix interaction. Furthermore, MEGF6 expression demonstrated a significant correlation with immune cell infiltration and the expression of immunosuppressive molecules, particularly CTLA-4, PD-1, PD-L1, TGF-β, and IL-10. In conclusion, our findings suggest that MEGF6 may play an oncogenic role by influencing cell and extracellular matrix interactions. Its overexpression may indicate immunosuppressive properties within the cancer microenvironment. Therefore, MEGF6 holds promise as a potential biomarker for predicting both prognosis and therapeutic responses in colon cancer. HIGHLIGHTS MEGF6 has been shown to involve colon cancer growth and chemotherapeutic resistance. Bioinformatics confirmed a prognostic significance of MEGF6 in colon cancer. MEGF6 may exert its oncogenic effects by influencing cell-matrix interactions. MEGF6 expression is correlated with immunosuppressive properties of cancers. GRAPHICAL ABSTRACT

Mechanism of 5-fluorouracil induced resistance and role of piperine and curcumin as chemo-sensitizers in colon cancer.

Among cancer-related deaths worldwide, colorectal cancer ranks second, accounting for 1.2% of deaths in those under 50years and 0.6% of deaths in those between 50 and 54years. The anticancer drug 5-fluorouracil is widely used to treat colorectal cancer. Due to a better understanding of the drug's mechanism of action, its anticancer activity has been increased through a variety of therapeutic alternatives. Clinical use of 5-FU has been severely restricted due to drug resistance. The chemoresistance mechanism of 5-FU is challenging to overcome because of the existence of several drug efflux transporters, DNA repair enzymes, signaling cascades, classical cellular processes, cancer stem cells, metastasis, and angiogenesis. Curcumin, a potent phytocompound derived from Curcuma longa, functions as a nuclear factor (NF)-κB inhibitor and sensitizer to numerous chemotherapeutic drugs. Piperine, an alkaloid found in Piper longum, inhibits cancer cell growth, causing cell cycle arrest and apoptosis. This review explores the mechanism of 5-FU-induced chemoresistance in colon cancer cells and the role of curcumin and piperine in enhancing the sensitivity of 5-FU-based chemotherapy. CLINICAL TRIAL REGISTRATION: Not applicable.

USP25 Elevates SHLD2-Mediated DNA Double-Strand Break Repair and Regulates Chemoresponse in Cancer.

DNA damage plays a significant role in the tumorigenesis and progression of the disease. Abnormal DNA repair affects the therapy and prognosis of cancer. In this study, it is demonstrated that the deubiquitinase USP25 promotes non-homologous end joining (NHEJ), which in turn contributes to chemoresistance in cancer. It is shown that USP25 deubiquitinates SHLD2 at the K64 site, which enhances its binding with REV7 and promotes NHEJ. Furthermore, USP25 deficiency impairs NHEJ-mediated DNA repair and reduces class switch recombination (CSR) in USP25-deficient mice. USP25 is overexpressed in a subset of colon cancers. Depletion of USP25 sensitizes colon cancer cells to IR, 5-Fu, and cisplatin. TRIM25 is also identified, an E3 ligase, as the enzyme responsible for degrading USP25. Downregulation of TRIM25 leads to an increase in USP25 levels, which in turn induces chemoresistance in colon cancer cells. Finally, a peptide that disrupts the USP25-SHLD2 interaction is successfully identified, impairing NHEJ and increasing sensitivity to chemotherapy in PDX model. Overall, these findings reveal USP25 as a critical effector of SHLD2 in regulating the NHEJ repair pathway and suggest its potential as a therapeutic target for cancer therapy.

Small molecules that disrupt RAD54-BLM interaction hamper tumor proliferation in colon cancer chemoresistance models.

RAD54 and BLM helicase play pivotal roles during homologous recombination repair (HRR) to ensure genome maintenance. BLM amino acids (aa 181-212) interact with RAD54 and enhance its chromatin remodeling activity. Functionally, this interaction heightens HRR, leading to a decrease in residual DNA damage in colon cancer cells. This contributes to chemoresistance in colon cancer cells against cisplatin, camptothecin, and oxaliplatin, eventually promoting tumorigenesis in preclinical colon cancer mouse models. ChIP-Seq analysis and validation revealed increased BLM and RAD54 corecruitment on the MRP2 promoter in camptothecin-resistant colon cancer cells, leading to BLM-dependent enhancement of RAD54-mediated chromatin remodeling. We screened the Prestwick small-molecule library, with the intent to revert camptothecin- and oxaliplatin-induced chemoresistance by disrupting the RAD54-BLM interaction. Three FDA/European Medicines Agency-approved candidates were identified that could disrupt this interaction. These drugs bound to RAD54, altered its conformation, and abrogated RAD54-BLM-dependent chromatin remodeling on G5E4 and MRP2 arrays. Notably, the small molecules also reduced HRR efficiency in resistant lines, diminished anchorage-independent growth, and hampered the proliferation of tumors generated using camptothecin- and oxaliplatin-resistant colon cancer cells in both xenograft and syngeneic mouse models in BLM-dependent manner. Therefore, the 3 identified small molecules can serve as possible viable candidates for adjunct therapy in colon cancer treatment.

Sensitization of colon cancer cells to cisplatin by Fbxw7 via negative regulation of the Nox1-mTOR pathway

Colorectal cancer (CRC) is a human malignancy which associates with high mortality rate and poor prognosis. Despite the initial effectiveness in clinical applications of chemotherapeutic agents, a fraction of patients develops chemoresistance. Fbxw7 is an F-box protein serving as a substrate recognition subunit of E3 ubiquitin ligase, leading to degradation of various oncoproteins. In this study, Fbxw7 was significantly downregulated in CRC tumors as well as CRC cells. Fbxw7 suppressed CRC cell proliferation and migration. Moreover, we observed Fbxw7 was positively associated with cisplatin sensitivity. Fbxw7 was significantly downregulated in cisplatin resistant CRC cells. Overexpression of Fbxw7 effectively increased the cisplatin sensitivity of cisplatin resistant CRC cells. Co-immunoprecipitation and GST pull-down assays showed Fbxw7 bond with Nox1 which was a superoxide-generating NADPH oxidase and showed oncogenic roles in colon cancer cells. Interestingly, Fbxw7 downregulated Nox1 through binding it to degrade Nox1 protein. We demonstrated that Fbxw7 negatively regulated mTOR activity through downregulation of Nox1. Finally, overexpression of Fbxw7 effectively increased the cisplatin sensitivity of CRC cells. This process could be further overturned by Nox1 restoration in Fbxw7-overexpressing colon cancer cells. In summary, these results unveiled that Fbxw7 targeted Nox1 for degradation, resulting in blocking the downstream Nox1-mTORC1 signaling to sensitize CRC cells to cisplatin. Our study potentiates that targeting the Fbxw7-Nox1-mTOR pathway could be an effective approach to overcome chemoresistance of colon cancer cells.

HOXB8 contributed to oxaliplatin chemo-resistance in colon cancer cells by activating STAT3

HOXB8 contributed to oxaliplatin chemo-resistance in colon cancer cells by activating STAT3

Abstract 2965: Epigenetic mechanisms involved in acquired resistance to combined chemotherapies in digestive cancer cells

Abstract Introduction. One of the challenges in the management of patients with cancer of the digestive tract is to prevent relapse. Epigenetic modifications (i.e. DNA methylation and histone marks) have been proven to be involved in the generation and maintenance of a subset of cells with stemness properties, that resist to conventional therapies. Our aim is to identify complexes of chromatin modifier enzymes (epienzymes) that are involved in acquired chemoresistance/aggressiveness of colon and pancreatic cancer cells. Experimental procedures/Methods. A meta-analysis performed on public transcriptomics data from colorectal cancer (CRC) patients cross-referenced with our own data including basal-like pancreatic cancer samples identified a limited number of epienzymes associated with aggressive subtypes of digestive cancers. Among them, the demethylase KDM4B, specific of the lysine 9 of Histone 3, and the transcriptional repressor PRDM1 where found correlated to the expression of several typical markers of cancer stemness. To confirm the role of these epienzymes in colon and pancreatic cancer cell chemoresistance, we have developed several in vivo and in vitro 2D and 3D models of acquired resistance to oxaliplatin-based combined chemotherapies, including FOLFIRINOX and FOLFOX. In this work, these models as well as patient samples have been used to study (i) the dynamic expression profile of these epienzymes (RT-qPCR, immunofluorescent multiplex staining, single-cell analysis and spatial transcriptomics), (ii) the gene regulons that are bound by these epienzymes (CUT&RUN-seq) and (iii) the functional role of these epienzymes in cancer stemness (organoid and sphere-forming assays). Results. We have shown that PRDM1 and KDM4B are expressed heterogeneously in cancer cell populations and overexpressed during specific time frames along the acquisition of resistance to oxaliplatin-based combined therapies both in colon and pancreatic cancer cells. Furthermore, we have obtained promising results regarding the binding of PRDM1 and KDM4B to key players of pluripotency/differentiation in chemoresistant colon cancer cells. Conclusions. Altogether, our data indicate that specific expression of chromatin modifier enzymes, most likely acting as epigenetic complexes, are key milestones of acquired resistance to conventional therapies. This work will pave the way for considering epienzyme-epienzyme interactions as potent drug targets that could circumvent cancer cell aggressiveness. Citation Format: Elsa Hadj Bachir, Charles Poiraud, Hugo Claux, Soumaya El Moghrabi, Sonia Paget, Belinda Duchêne, Nicolas Jonckheere, Bernadette Neve, Emmanuelle Leteurtre, Isabelle Van Seuningen, Audrey Vincent. Epigenetic mechanisms involved in acquired resistance to combined chemotherapies in digestive cancer cells [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 2965.

Danshensu Attenuated Epithelial-Mesenchymal Transformation and Chemoresistance of Colon Cancer Cells Induced by Platelets.

The interactions between platelets and tumor cells are well-known to play important roles in the progression of malignant tumors. Danshensu, a main water-soluble component of Salvia miltiorrhiza, can resist platelet aggregation and exert significant anti-tumor effects on various types of tumors. However, whether Danshensu could inhibit the progression of malignant tumors by suppressing the activities of platelets had not been reported. The effects of Danshensu on the platelet activity and epithelial-mesenchymal transformation (EMT)-like invasive phenotype of SW620 colon cancer cells were assessed by stimulating with the supernatants from co-cultured platelets and SW620 cells with direct contact (SCP). The expression and secretion of proteins were determined by western blot and enzyme-linked immunosorbent assay (ELISA), respectively. Hematoxylin and eosin (H&E) staining was performed to analyzed the histopathology of tumor tissues and immunohistochemical staining was conducted to examine the protein expression in tumors. Co-incubation of SW620 cells with platelets directly or SCP both generated long spindle-shaped invasive phenotype. Pretreatment of platelets with Danshensu (25 μM) inhibited the morphological changes of SW620 cells induced by SCP, which was associated with the inhibitory effects of Danshensu on platelet secretion. Danshensu diminished the secretion of a list of biological factors in SCP, including interleukin (IL)-6, tumor necrosis factor alpha (TNF-α), IL-1β and vascular endothelial growth factor (VEGF) that are all involved in tumor cell EMT and chemoresistance. Moreover, Danshensu up-regulated the expression of E-cadherin but down-regulated the levels of N-cadherin and Vimentin, resulting in the repression of SW620 cell migration. It was also shown that Danshensu enhanced the sensitivity of SW620 cells to oxaliplatin by suppressing the expression of MDR1. Furthermore, Danshensu could not only reduced the growth of subcutaneous tumors and liver metastasis that induced by SCP, but also down-regulated the expression of MDR1 in vivo. Mechanistic studies revealed that Danshensu suppressed the activation of the TGF-β/Smad signaling pathway. Danshensu attenuated EMT-like characteristics and chemoresistance by inhibiting secretion capability of platelets and activation of the TGF-β/Smad signaling pathway, suggesting that it may be optimized to be a therapeutic agent for fighting against colon cancer.

The POU2F1-ALDOA axis promotes the proliferation and chemoresistance of colon cancer cells by enhancing glycolysis and the pentose phosphate pathway activity

Cancer metabolic reprogramming enhances its malignant behaviors and drug resistance, which is regulated by POU domain transcription factors. This study explored the effect of POU domain class 2 transcription factor 1 (POU2F1) on metabolic reprogramming in colon cancer. The POU2F1 expression was analyzed in GEO dataset, TCGA cohorts and human colon cancer tissues by bioinformatics and immunohistochemistry. The effects of altered POU2F1 expression on proliferation, glucose metabolism and oxaliplatin sensitivity of colon cancer cells were tested. The impacts of POU2F1 on aldolase A (ALDOA) expression and malignant behaviors of colon cancer cells were examined. We found that up-regulated POU2F1 expression was associated with worse prognosis and oxaliplatin resistance in colon cancer. POU2F1 enhanced the proliferation, aerobic glycolysis and the pentose phosphate pathway (PPP) activity, but reduced oxidative stress and apoptosis in colon cancer cells, dependent on up-regulating ALDOA expression. Mechanistically, POU2F1 directly bound to the ALDOA promoter to enhance the ALDOA promoter activity in colon cancer cells. Moreover, activation of the POU2F1-ALDOA axis decreased the sensitivity to oxaliplatin in colon cancer cells. These data indicate that the POU2F1-ALDOA axis promotes the progression and oxaliplatin resistance by enhancing metabolic reprogramming in colon cancer. Our findings suggest that the POU2F1-ALDOA axis may be new therapeutic targets to overcome oxaliplatin resistance in colon cancer.

Knockdown of OLR1 weakens glycolytic metabolism to repress colon cancer cell proliferation and chemoresistance by downregulating SULT2B1 via c-MYC

Chemoresistance is one of the major problems of colon cancer treatment. In tumors, glycolytic metabolism has been identified to promote cell proliferation and chemoresistance. However, the molecular mechanisms underlying glycolytic metabolism and chemoresistance in colon cancer remains enigmatic. Hence, this research was designed to explore the mechanism underlying the OLR1/c-MYC/SULT2B1 axis in the regulation of glycolytic metabolism, to affect colon cancer cell proliferation and chemoresistance. Colon cancer tissues and LoVo cells were attained, where OLR1, c-MYC, and SULT2B1 expression was detected by immunohistochemistry, RT-qPCR, and western blot analysis. Next, ectopic expression and knockdown assays were implemented in LoVo cells. Cell proliferation was detected by MTS assay and clone formation. Extracellular acidification, glucose uptake, lactate production, ATP/ADP ratio, and GLUT1 and LDHA expression were measured to evaluate glycolytic metabolism. Then, the transfected cells were treated with chemotherapeutic agents to assess drug resistance by MTS experiments and P-gp and SMAD4 expression by RT-qPCR. A nude mouse model of colon cancer transplantation was constructed for in vivo verification. The levels of OLR1, c-MYC, and SULT2B1 were upregulated in colon cancer tissues and cells. Mechanistically, OLR1 increased c-MYC expression to upregulate SULT2B1 in colon cancer cells. Moreover, knockdown of OLR1, c-MYC, or SULT2B1 weakened glycolytic metabolism, proliferation, and chemoresistance of colon cancer cells. In vivo experiments authenticated that OLR1 knockdown repressed the tumorigenesis and chemoresistance in nude mice by downregulating c-MYC and SULT2B1. Conclusively, knockdown of OLR1 might diminish SULT2B1 expression by downregulating c-MYC, thereby restraining glycolytic metabolism to inhibit colon cancer cell proliferation and chemoresistance.

TrkB/C-induced HOXC6 activation enhances the ADAM8-mediated metastasis of chemoresistant colon cancer cells.

The abnormal expression of tropomyosin receptor kinase(Trk) serves an important role in the promotion of cancer progression. HomeoboxC6(HOXC6) and Adisintegrin and metalloproteinase domain‑containing8(ADAM8) are associated with the invasiveness of cancer cells. However, the exact relationship between these molecules and their downstream signaling pathways in chemoresistant colon cancer cells are largely unknown. Therefore, the current study investigated the association between TrkB/C with HOXC6 and ADAM8 in the induction of drug‑resistant colon cancer cell metastasis. The results demonstrated that chemoresistant colon cancer cells exhibited upregulated TrkB/C, HOXC6 and ADAM8 expression. Additionally, but also chemoresistant colon cancer cells demonstrated higher migratory activities compared with parent colon cancer cells. The pharmacological inhibition of TrkB/C activity reduced the phosphorylation of mitogen‑activated protein kinase kinase/ERK and subsequently suppressed HOXC6 and ADAM8 expression. In addition, gene silencing of HOXC6 inhibited ADAM8 and MMP activity, and inhibited the migration and invasion of drug‑resistant cancer cells. However, the targeted downregulation of ADAM8 using small interfering RNA failed to suppress TrkB/C‑associated ERK‑mediated HOXC6 signaling activity. Furthermore, pre‑treatment with ADAM10‑ and ADAM17‑specific inhibitors had no effect on attenuating the invasiveness of chemoresistant colon cancer cells. The results indicated that TrkB/C‑mediated ERK activation serves an important role in the metastasis of drug‑resistant colon cancer cells through the regulation of HOXC6/ADAM8 activity.

Impedance-based drug-resistance characterization of colon cancer cells through real-time cell culture monitoring

Interest in impedance-based cellular assays is rising due to their remarkable advantages, including label-free, low cost, non-invasive, non-destructive, quantitative and real-time monitoring. In order to test their potential in cancer treatment decision and early detection of chemoresistance, we devised a new custom-made impedance measuring system based on electric cell-substrate impedance sensing (ECIS), optimized for long term impedance measurements. This device was employed in a proof of concept cell culture impedance analysis for the characterization of chemo-resistant colon cancer cells. Doxorubicin-resistant HT-29 cells were used for this purpose and monitored for 140 h. Analysis of impedance-based curves reveal different trends from chemo-sensitive and chemo-resistant cells. An impedance-based cytoxicity assay with different concentrations of doxorubicin was also performed using ECIS. The obtained results confirm the feasibility of ECIS in the study of drug resistance and show promises for studies of time-dependent factors related to physiological and behavioral changes in cells during resistance acquisition. The methodology presented herein, allows the continuous monitoring of cells under normal culture conditions as well as upon drug exposure. The ECIS device used, sets the basis for high-throughput early detection of resistance to drugs, administered in the clinical practice to cancer patients, and for the screening of new drugs in vitro, on patient-derived cells.

LINC01123 facilitates proliferation, invasion and chemoresistance of colon cancer cells.

Colon cancer is one of the major causes of cancer-related deaths worldwide. Long non-coding RNA (lncRNA) LINC01123 has been suggested to act as an oncogene in non-small cell lung cancer and a prognostic signature in head and neck squamous cell carcinoma. However, its role in colon cancer remains obscure. From TCGA database, LINC01123 was observed to be up-regulated in colon adenocarcinoma (COAD). Subsequently, the up-regulated LINC01123 was also detected in colon cancer cells. Functionally, LINC01123 could enhance cell proliferation, migration, invasion and angiogenesis. Moreover, the chemoresistance of colon cancer cells was verified to be promoted by LINC01123. Afterward, LINC01123 was found to bind with Ago2 and miR-34c-5p. Besides, miR-34c-5p was confirmed to inhibit the cellular process and chemoresistance of colon cancer cells. Then, VEGFA was disclosed to coexist with LINC01123 and miR-34c-5p in RNA-induced silencing complex. And TCGA database suggested that its expression was correlated with different stages of COAD. Moreover, it was uncovered that VEGFA could bind with miR-34c-5p and its expression positively correlated with LINC01123 expression. Finally, LINC01123 was proofed to regulate colon cancer progression and cells chemoresistance via VEGFA. In conclusion, LINC01123/miR-34c-5p/VEGFA axis promotes colon cancer malignancy and cells chemoresistance.

Different effects of lysophosphatidic acid receptor-2 (LPA2) and LPA5 on the regulation of chemoresistance in colon cancer cells

Lysophosphatidic acid (LPA) is a simple physiological lipid and exhibits several biological functions by binding to G-protein-coupled LPA receptors (LPA receptor-1 (LPA1) to LPA6). The present study aimed to evaluate whether LPA signaling via LPA2 and LPA5 is involved in the chemoresistance to anticancer drugs in colon cancer DLD1 cells. In cell survival assay, cells were treated with fluorouracil (5-FU) every 24 h for 2 days. The cell survival rate to 5-FU of DLD1 cells was significantly decreased by LPA treatment. In the presence of LPA, the cell survival rate to 5-FU was significantly elevated by LPA5 knockdown. Before initiation of the cell survival assay, cells were pretreated with an LPA2 agonist, GRI-977143. The cell survival rate to 5-FU was markedly increased in DLD1 cells treated with GRI-977143. In the presence of GRI-977143, the elevated cell survival rate of DLD1 cells was reduced by LPA2 knockdown. To assess the effects of LPA2 and LPA5 on the enhancement of chemoresistance, long-term 5-FU treated (DLD-5FU) cells were generated from DLD1 cells. The cell survival rate to 5-FU of DLD-5FU cells were significantly elevated by LPA5 knockdown. GRI-977143 treatment increased the cell survival rate to 5-FU of DLD-5FU cells. These results suggest that LPA2 promotes and LPA5 suppresses the acquisition of chemoresistance in colon cancer cells treated with anticancer drugs.

GLUT5 regulation by AKT1/3-miR-125b-5p downregulation induces migratory activity and drug resistance in TLR-modified colorectal cancer cells.

In cancer, resistance to chemotherapy is one of the main reasons for therapeutic failure. Cells that survive after treatment with anticancer drugs undergo various changes, including in cell metabolism. In this study, we investigated the effects of AKT-mediated miR-125b-5p alteration on metabolic changes and examined how these molecules enhance migration and induce drug resistance in colon cancer cells. AKT1 and AKT3 activation in drug-resistant colon cancer cells caused aberrant downregulation of miR-125b-5p, leading to GLUT5 expression. Targeted inhibition of AKT1 and AKT3 restored miR-125b-5p expression and prevented glycolysis- and lipogenesis-related enzyme activation. In addition, restoring the level of miR-125b-5p by transfection with the mimic sequence not only significantly blocked the production of lactate and intracellular fatty acids but also suppressed the migration and invasion of chemoresistant colon cancer cells. GLUT5 silencing with small interfering RNA attenuated mesenchymal marker expression and migratory activity in drug-resistant colon cancer cells. Additionally, treatment with 2,5-anhydro-d-mannitol resensitized chemoresistant cancer cells to oxaliplatin and 5-fluorouracil. In conclusion, our findings suggest that changes in miR-125b-5p and GLUT5 expression after chemotherapy can serve as a new marker to indicate metabolic change-induced migration and drug resistance development.

MiRNA-29a reverses P-glycoprotein-mediated drug resistance and inhibits proliferation via up-regulation of PTEN in colon cancer cells

Colon cancer is a serious malignant type of cancer in the world. Acquisition of multi-drug resistance (MDR) during chemotherapy is still a controversial challenge during cancer treatment. Accordingly, detection of safe and impressive MDR-reversing targets such as microRNAs (miRNAs/miRs) can play critical role in cancer treatment. Here, the functional effects of miR-29a in chemo-resistant colon cancer cells is scrutinized. The effect of doxorubicin (DOX) on cell proliferation after miR-29a transfection has been evaluated using MTT assay in HT29 and HT29/DOX cells. Rhodamine123 (Rh123) assay is used to identify the activity of common drug efflux through membrane transporters P-glycoprotein (P-gp). P-gp and PTEN mRNA/protein expression levels were measured by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and Western blot analyses. Flow cytometry was employed to the investigation of apoptosis. ANOVA followed by Bonferroni's and Sidak's tests were used to compare the data from different groups. Thus, it was shown that miRNA-29a overexpression considerably inhibited the HT29/DOX viability. miR-29a significantly down-regulated P-gp expression and activity in HT29/DOX cells and declined drug resistance through elevation of intracellular DOX. Furthermore, upon miRNA-29a transfection, PTEN expression could be restored in resistant cells. These results have indicated that miR-29a target PTEN ultimately P-gp, which is downstream of PTEN, inhibit drug resistance, proliferation, and apoptosis through PI3K/Akt pathway. As a result, miR-29a overexpression is led to enhance the sensitivity of HT29/DOX cells to DOX-treatment by targeting P-gp. MiR-29a might proffer a novel promising candidate for colon cancer therapeutics during chemotherapy.

β-Lactams with antiproliferative and antiapoptotic activity in breast and chemoresistant colon cancer cells

A series of novel 1,4-diaryl-2-azetidinone analogues of combretastatin A-4 (CA-4) have been designed, synthesised and evaluated in vitro for antiproliferative activity, antiapoptotic activity and inhibition of tubulin polymerisation. Glucuronidation of CA-4 by uridine 5-diphosphoglucuronosyl transferase enzymes (UGTs) has been identified as a mechanism of resistance in cancer cells. Potential sites of ring B glucuronate conjugation are removed by replacing the B ring meta-hydroxy substituent of selected series of β-lactams with alternative substituents e.g. F, Cl, Br, I, CH3. The 3-phenyl-β-lactam 11 and 3-hydroxy-β-lactam 46 demonstrate improved activity over CA-4 in CA-4 resistant HT-29 colon cancer cells (IC50 = 9 nM and 3 nM respectively compared with IC50 = 4.16 μM for CA-4), while retaining potency in MCF-7 breast cancer cells (IC50 = 17 nM and 22 nM respectively compared with IC50 = for 4 nM for CA-4). Compound 46 binds at the colchicine site of tubulin, and strongly inhibits tubulin assembly at micromolar concentrations comparable to CA-4. In addition, compound 46 induced mitotic arrest at low concentration in both cell lines MCF-7 and HT-29 together with downregulation of expression of antiapoptotic proteins Mcl-1, Bcl-2 and survivin in MCF-7 cells. These novel antiproliferative and antiapoptotic β-lactams are potentially useful scaffolds in the development of tubulin-targeting agents for the treatment of breast cancers and chemoresistant colon cancers.

Modified TLR-mediated downregulation of miR-125b-5p enhances CD248 (endosialin)-induced metastasis and drug resistance in colorectal cancer cells.

CD248, also called endosialin or tumor endothelial marker-1, is markedly upregulated in almost all cancers, including colon cancers. Changes in microRNA profiles are one of the direct causes of cancer development and progression. In this study, we investigated whether a change in CD248 expression in colon cancer cells could induce drug resistance after chemotherapy, and we explored the relationship between miR-125b-5p levels and CD248 expression in Toll-like receptor (TLR)-modified chemoresistant colon cancer cells. TLR2/6 and TLR5 upregulation in drug-resistant colon cancer cells contributed to miR-125b-5p downregulation and specificity protein 1 (Sp1)-mediated CD248 upregulation via nuclear factor-kappa B (NF-κB) activation. Exposure to specific TLR2/6 or TLR5 ligands enhanced the expression of mesenchymal markers as well as the migratory activity of oxaliplatin- or 5-fluorouracil-resistant colon cancer cells. The transfection of a synthetic miR-125b-5p mimic into chemoresistant cells prevented Sp1 and CD248 activation and significantly impaired invasive activity. Furthermore, Sp1 or CD248 gene silencing as well as miR-125b-5p overexpression markedly reversed drug resistance and inhibited epithelial-mesenchymal transition in colon cancer cells. Taken together, these results suggest that changes in miR-125b-5p levels play an important role in Sp1-mediated CD248 expression and the development of drug resistance in TLR-mutated colon cancer cells.

Enhancement of chemosensitivity in 5-fluorouracil-resistant colon cancer cells with carcinoembryonic antigen-specific RNA aptamer.

Colorectal cancer (CRC) is one of the most common cancers, and rates of incidence and diagnosis of CRC have gradually increased. Carcinoembryonic antigen (CEA) is overexpressed in patients with CRC and is associated with cell adhesion, anoikis resistance, and promotion of metastasis to the liver. 5-Fluorouracil (5-FU) is a chemotherapeutic drug used to treat cancer, including CRC. However, a major issue of 5-FU therapy is the occurrence of chemoresistance, and the fact that 5-FU induces CEA overexpression, which may induce the 5-FU resistance. We previously isolated a CEA-specific RNA aptamer that was able to inhibit hepatic metastasis of colon cancer cells in a mouse model. In the present study, we tested whether protecting CEA using the CEA aptamer could enhance 5-FU sensitivity in chemoresistant LS174T colon cancer cells. We observed that the CEA aptamer sensitized the 5-FU-resistant colon cancer cell line to 5-FU more than five-fold (IC50 ~ 5.995μM), compared with cells treated with 5-FU alone (IC50 ~ 31.46μM). Moreover, treatment with CEA aptamer combined with 5-FU synergistically regressed growth of chemoresistant tumors in mouse xenografted models. Combinatorial treatment of 5-FU and CEA aptamer augmented caspase-8 activity in the 5-FU-resistant colon cancer cell line via aptamer-mediated disruption of CEA interaction with death receptor 5 and in mouse xenograft tumors. In conclusion, CEA-specific aptamer improved 5-FU sensitivity in chemoresistant colon cancer cells in vitro and in vivo, and thus represents a novel 5-FU adjuvant to overcome the chemoresistance in CRC patients.

PTPRK suppresses progression and chemo-resistance of colon cancer cells via direct inhibition of pro-oncogenic CD133.

Receptor‐type protein tyrosine phosphatase κ (PTPRK) is considered to be a candidate tumor suppressor. PTPRK dephosphorylates CD133, which is a stem cell marker; phosphorylated CD133 accelerates xenograft tumor growth of colon cancer cells through the activation of AKT, but the functional significance of this has remained elusive. In this study, we have demonstrated that knockdown of PTPRK potentiates the pro‐oncogenic CD133–AKT pathway in colon cancer cells. Intriguingly, depletion of PTPRK significantly reduced sensitivity to the anti‐cancer drug oxaliplatin and was accompanied by up‐regulation of phosphorylation of Bad, a downstream target of AKT. Together, our present observations strongly suggest that the CD133–PTPRK axis plays a pivotal role in the regulation of colon cancer progression as well as drug resistance.