sphingosine-kinase and Colorectal-Neoplasms

Sphingosine kinase 1 (Sphk1) is a highly conserved lipid kinase that phosphorylates sphingosine to form sphingosine-1-phosphate (S1P). Growing studies have demonstrated that Sphk1 is overexpressed in various types of solid cancers and can be induced by growth factors, cytokines, and carcinogens, leading to the increase of S1P production. Subsequently, the increased Sphk1/S1P facilitates cancer cell proliferation, mobility, angiogenesis, invasion, and metastasis. Therefore, Sphk1/S1P signaling plays oncogenic roles. This review summarizes the features of Sphk1/S1P signaling and their functions in colorectal cancer cell growth, tumorigenesis, and metastasis, as well as the possible underlying mechanisms.

Topics: Animals; Cell Movement; Cell Proliferation; Colorectal Neoplasms; Humans; Lysophospholipids; Phosphotransferases (Alcohol Group Acceptor); Signal Transduction; Sphingosine

The sphingosine kinase-2 (SphK2), a main component of sphingolipid signal transduction, is reported as an innovative therapeutic candidate for cancer treatment. This study was conducted to investigate the suppression of SphK2 in increasing HT-29 colorectal cancer cells sensitivity to paclitaxel via inducing apoptosis and targeting c-FLIPS, MCL-1, and survivin expressions. Cells were transfected with siRNA against SphK2, PTX, or SphK2 activator. Proliferation and apoptosis were evaluated by MTT assay, and trypan blue staining and ELISA, respectively. SphK2, c-FLIPS, MCL-1, and survivin expression were determined by qRT-PCR and Western blotting. SphK2 siRNA increased cell death induced PTX. SphK2 agonist abolished silencing impact on cell survival. We found down-expression of C-FLIPS, MCL-1, and survivin by SphK2 siRNA transfection either alone or in paclitaxel treated cells, as well as elevation in cell apoptosis. Our results showed that SphK2 suppression may be an effective important modality to enhance cell sensitivity to paclitaxel via the induction of apoptosis in colorectal cancers.

Topics: Apoptosis; Cell Line, Tumor; Cell Proliferation; Colorectal Neoplasms; Humans; Myeloid Cell Leukemia Sequence 1 Protein; Paclitaxel; RNA, Small Interfering; Survivin

Topics: Antineoplastic Agents; Biomarkers, Tumor; Colorectal Neoplasms; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; Molecular Targeted Therapy; Neoplastic Stem Cells; Phosphotransferases (Alcohol Group Acceptor); Prognosis; Stem Cell Niche

Aberrant gene expression plays critical roles in the development of colorectal cancer (CRC). Here we show that POTEE, which was identified as a member E of POTE ankyrin domain family, was significantly upregulated in colorectal tumors and predicted poor overall survival of CRC patients. In CRC cells, POTEE could act as an oncogene and could promote cell growth, cell-cycle progression, inhibit apoptosis, and elevates xenograft tumor growth. Mechanically, we used microarray analysis and identified a POTEE/SPHK1/p65 signaling axis, which affected the biological functions of CRC cells. Further evaluation showed that overexpression of POTEE could increase the protein expression of SPHK1, followed by promoting the phosphorylation and activation of p65 protein. Altogether, our findings suggested a POTEE/SPHK1/p65 signaling axis could promote colorectal tumorigenesis and POTEE might potentially serve as a novel biomarker for the diagnosis and an intervention of colorectal cancer.

Topics: Aged; Antigens, Neoplasm; Carcinogenesis; Cell Line, Tumor; Cell Movement; Colorectal Neoplasms; Disease-Free Survival; eIF-2 Kinase; Female; Gene Expression Regulation, Neoplastic; Humans; Lymphatic Metastasis; Male; Middle Aged; Phosphotransferases (Alcohol Group Acceptor); Signal Transduction

It was demonstrated that Sphingosine kinase 1 (SphK1) promotes tumor progression and confers the malignancy phenotype of colorectal cancer by activating the focal adhesion kinase (FAK) pathway. However, further clarification is required to determine if SphK1 promotes the metastasis of colorectal cancer by inducing epithelial‑mesenchymal transition (EMT), and its mechanisms have not been fully elucidated. Immunohistochemistry staining was used to detect protein expression in normal colonic mucosa tissues and colorectal cancer tissues. Cells were transfected to overexpress SphK1, downregulate SphK1 or downregulate FAK. An MTT assay was used to detect the drug toxicity to cells. Transwell and wound healing assays were used to detect cell migration ability. Reverse transcription‑polymerase chain reaction and western blot analysis were used to detect the expression of mRNA and protein, respectively. Scanning electron microscopy was used to observe the microvilli and pseudopodia of the cells. The analysis of protein expression in 114 human colorectal cancer tissues demonstrated that the expressions of SphK1, FAK, phosphorylated (p)‑FAK, E‑cadherin and vimentin were associated with the metastasis of colorectal cancer. Furthermore, the patients with colorectal cancer with SphK1‑positive cancer demonstrated poorer prognosis compared with SphK1‑negative cancer. FAK knockdown and SphK1 knockdown of human colon cancer RKO cells inhibited the EMT and migrational potency, along with the expression of p‑FAK, p‑protein kinase B (AKT) and matrix metalloproteinase (MMP)2/9. In contrast, SphK1 overexpression promoted EMT, migrational potency, and the expression of p‑FAK, p‑AKT and MMP2/9 in HT29 cells. Additionally, the EMT and migrational potency of SphK1‑overexpressing HT29 cells was suppressed by a FAK inhibitor, and the expression of p‑FAK, p‑AKT and MMP2/9 was suppressed by blocking the FAK pathway. In conclusion, SphK1 promoted the migration and metastasis of colon cancer by inducing EMT mediated by the FAK/AKT/MMPs axis.

Topics: Adult; Aged; Aged, 80 and over; Cell Line, Tumor; Colorectal Neoplasms; Epithelial-Mesenchymal Transition; Female; Focal Adhesion Protein-Tyrosine Kinases; HT29 Cells; Humans; Male; Matrix Metalloproteinases; Middle Aged; Neoplasm Metastasis; Neoplasm Staging; Phosphotransferases (Alcohol Group Acceptor); Proto-Oncogene Proteins c-akt; Signal Transduction; Survival Analysis

Sphingosine kinase 1 (SPHK1) is up-regulated in many different cancers and plays a crucial role in tumor development and progression. However, the prognostic value of SPHK1 in colorectal cancer (CRC) remains unclear.. The expression of SPHK1 in CRC cell lines and 328 CRC tissue samples was examined. It was also investigated whether SPHK1 expression is associated with clinicopathological characteristics and outcomes in patients with CRC.. HCT 116 and HT-29 cells expressed significantly higher SPHK1 levels than did CCD 841 CoTr. On immunohistochemistry, SPHK1 expression was significantly higher in CRC tissue than in normal colonic mucosal tissue, with 34.1% of CRC patients exhibiting high SPHK1 expression. High SPHK1 expression in CRC was significantly associated with higher histological grade, deeper invasion depth, lymphatic invasion, vascular invasion, and development of distant metastasis, and was shown to be an independent predictor of distant metastasis. Furthermore, patients with high SPHK1 expression had significantly lower overall survival rates than those with low expression.. High SPHK1 expression was significantly associated with aggressive CRC behavior and worse overall survival, and was an independent predictor of distant metastasis. SPHK1 may thus be a potential prognostic biomarker and therapeutic target in CRC patients.

Topics: Aged; Biomarkers, Tumor; Cell Line, Tumor; Colorectal Neoplasms; Disease Progression; Female; HCT116 Cells; HT29 Cells; Humans; Immunohistochemistry; Lymphatic Metastasis; Male; Middle Aged; Neoplasm Invasiveness; Neoplasm Metastasis; Phosphotransferases (Alcohol Group Acceptor); Prognosis; Treatment Outcome

LncRNA MEG3 is involved in the pathogenesis of several types of cancers. While its participation and function network in colorectal (CR) adenocarcinoma, which is one of the most common malignancies, still hasn't been well studied. Therefore, our study aimed to investigate the role of MEG3 in colorectal adenocarcinoma and to explore the possibly related mechanisms.. Tumor tissues and adjacent healthy tissues were collected from colorectal adenocarcinoma patients. Blood samples were collected from both colorectal adenocarcinoma patients and healthy controls to prepare serum sample. Expression of MEG3 in those tissues was detected by qRT-PCR. MEG3 knockdown and sphingosine kinase 1 (SPHK1) overexpression colorectal adenocarcinoma cell lines were established. Its effects on cell proliferation and apoptosis were investigated by CCK-8 assay and MTT assay, respectively. Effects of MEG3 overexpression on TGF-β1 and SPHK1 were investigated by Western blot.. MEG3 expression level was decreased in tumor tissues than that in adjacent healthy tissues. Serum level of MEG3 was lower in cancer patients than that in healthy controls, and the serum level decreased with the increased stage of primary tumor. Serum TGF-β1 can be used to predict colorectal adenocarcinoma and its prognosis accurately. MEG3 knockdown and SPHK1 overexpression promoted tumor cell proliferation, but inhibited cell apoptosis. MEG3 knockdown also increased the expression level of TGF-β1 and SPHK1. Treatment with TGF-β1 inhibitor reduced the expression level of SPHK1 but showed no significant effects on MEG3. SPHK1 overexpression showed no significant effects on MEG3 and TGF-β1 expression.. Downregulation of lncRNA MEG3 can promote colorectal adenocarcinoma cell proliferation and inhibit the apoptosis by up-regulating TGF-β1 and its downstream sphingosine kinase 1.

Topics: Adenocarcinoma; Adult; Aged; Apoptosis; Case-Control Studies; Cell Line, Tumor; Cell Proliferation; Colorectal Neoplasms; Down-Regulation; Female; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Neoplastic; Humans; Male; Middle Aged; Phosphotransferases (Alcohol Group Acceptor); RNA, Long Noncoding; Signal Transduction; Transforming Growth Factor beta1; Young Adult

Sphingosine kinase 1 (SphK1) plays an important role in colorectal carcinoma metastasis. However, whether SphK1 modulates epithelial-mesenchymal transition (EMT)-related marker expression and the underlying mechanisms remain unclear. In this study, in order to clarify this issue, we used various colorectal cancer (CRC) cell lines, Caco2, HT29, RKO and HCT116. Each of the cell lines was divided into 3 groups as follows: the control group, SKI-Ⅱ (SphK1 inhibitor) group and PF-562271 [focal adhesion kinase (FAK) inhibitor] group. The migratory ability of the cells was examined by Transwell chamber assay. The mRNA and protein expression levels of SphK1, FAK (p-FAK), Slug, vimentin, N-cadherin and E-cadherin were detected by PCR and western blot analysis, respectively. The results revealed that the suppression of SphK1 reduced the cell migratory ability, and decreased the expression of Slug, vimentin and N-cadherin; however, the expression of E-cadherin was increased. Moreover, the inhibition of SphK1 reduced the expression of p-FAK. The inhibition of FAK (p-FAK) also decreased the cell migratory ability, and decreased the expression of Slug, vimentin and N-cadherin, whereas the expression of E-cadherin was increased. Thus, our data suggest that SphK1 modulates the expression of EMT-related markers and cell migration by regulating the expression of p-FAK in CRC cells. Thus, SphK1 may play a functional role in mediating the EMT process in CRC.

Topics: Biomarkers; Cadherins; Cell Line, Tumor; Cell Movement; Colorectal Neoplasms; Epithelial-Mesenchymal Transition; Focal Adhesion Protein-Tyrosine Kinases; Gene Expression Regulation, Neoplastic; Humans; Phosphotransferases (Alcohol Group Acceptor); RNA, Messenger; Vimentin

AKT is often hyper-activated in human colorectal cancers (CRC). This current study evaluated the potential anti-CRC activity by AT7867, a novel AKT and p70S6K1 (S6K1) dual inhibitor. We showed that AT7867 inhibited survival and proliferation of established (HT-29, HCT116 and DLD-1 lines) and primary human CRC cells. Meanwhile, it provoked caspase-dependent apoptosis in the CRC cells. Molecularly, AT7867 blocked AKT-S6K1 activation in CRC cells. Restoring AKT-S6K1 activation, via expression of a constitutively-active AKT1 ("ca-AKT1"), only partially attenuated AT7867-induced HT-29 cell death. Further studies demonstrated that AT7867 inhibited sphingosine kinase 1 (SphK1) activity to promote pro-apoptotic ceramide production in HT-29 cells. Such effects by AT7867 were independent of AKT inhibition. AT7867-indued ceramide production and subsequent HT-29 cell apoptosis were attenuated by co-treatment of sphingosine-1-phosphate (S1P), but were potentiated with the glucosylceramide synthase (GCS) inhibitor PDMP. In vivo, intraperitoneal injection of AT7867 inhibited HT-29 xenograft tumor growth in nude mice. AKT activation was also inhibited in AT7867-treated HT-29 tumors. Together, the preclinical results suggest that AT7867 inhibits CRC cells via AKT-dependent and -independent mechanisms.

Topics: Animals; Apoptosis; Cell Line, Tumor; Colorectal Neoplasms; Enzyme Activation; Humans; Mice; Mice, Nude; Phosphotransferases (Alcohol Group Acceptor); Piperidines; Proto-Oncogene Proteins c-akt; Pyrazoles; Ribosomal Protein S6 Kinases, 70-kDa; Xenograft Model Antitumor Assays

Colorectal cancer (CRC) is one of the most common cancers worldwide. Sphingosine kinase 1 (SphK1), which phosphorylates sphingosine to sphingosine-1-phosphate (S1P), is overexpressed in various types of cancers and may act as an oncogene in tumorigenesis. However, little is known about the role of SphK1 in CRC patients. We studied the expression of SphK1 in 85 cases of CRC tissues by immunohistochemistry, qRT-PCR, and western blot. We also evaluated the effect of SphK1 on cell proliferation and invasion by MTT and transwell invasion assay. SphK1 is overexpressed in CRC tissues and cell lines, and upregulation of SphK1 correlated significantly with the following parameters: lymph node metastasis, liver metastasis, and advanced TNM stage. SphK1 knockdown results in inhibition of cancer cell proliferation. Inhibition of CRC cell migration and invasion is also evident through reversal of EMT by increases in E-cadherin expression and decreases in vimentin expression. In conclusion, SphK1 is associated with the proliferation and invasiveness of CRC cells and the SphK1 gene may contribute to a novel therapeutic approach against CRC.

Topics: Cell Line, Tumor; Cell Movement; Cell Survival; Colorectal Neoplasms; Female; Gene Expression; Humans; Male; Phosphotransferases (Alcohol Group Acceptor); RNA, Messenger; RNA, Small Interfering

In this study, we showed that PF-543, a novel sphingosine kinase 1 (SphK1) inhibitor, exerted potent anti-proliferative and cytotoxic effects against a panel of established (HCT-116, HT-29 and DLD-1) and primary human colorectal cancer (CRC) cells. Its sensitivity was negatively associated with SphK1 expression level in the CRC cells. Surprisingly, PF-543 mainly induced programmed necrosis, but not apoptosis, in the CRC cells. CRC cell necrotic death was detected by lactate dehydrogenase (LDH) release, mitochondrial membrane potential (MMP) collapse and mitochondrial P53-cyclophilin-D (Cyp-D) complexation. Correspondingly, the necrosis inhibitor necrostatin-1 largely attenuated PF-543-induced cytotoxicity against CRC cells. Meanwhile, the Cyp-D inhibitors (sanglifehrin A and cyclosporin A), or shRNA-mediated knockdown of Cyp-D, remarkably alleviated PF-543-induced CRC cell necrotic death. Reversely, over-expression of wild-type Cyp-D in HCT-116 cells significantly increased PF-543's sensitivity. In vivo, PF-543 intravenous injection significantly suppressed HCT-116 xenograft growth in severe combined immunodeficient (SCID) mice, whiling remarkably improving the mice survival. The in vivo activity by PF-543 was largely attenuated when combined with the Cyp-D inhibitor cyclosporin A. Collectively, our results demonstrate that PF-543 exerts potent anti-CRC activity in vitro and in vivo. Mitochondrial programmed necrosis pathway is likely the key mechanism responsible for PF-543's actions in CRC cells.

Topics: Animals; Apoptosis; Cell Line, Tumor; Cell Survival; Colorectal Neoplasms; Dose-Response Relationship, Drug; Female; Methanol; Mice; Mice, SCID; Phosphotransferases (Alcohol Group Acceptor); Pyrrolidines; Sulfones; Survival Rate; Treatment Outcome

To examine the expression of SphK1, an oncogenic kinase that produces sphingosine 1-phosphate (S1P), and its correlation with the expression of LPAR2, a major lysophosphatidic acid (LPA) receptor overexpressed in various cancers, in human colorectal cancer.. Real-time reverse-transcription polymerase chain reaction was used to measure the mRNA expression of SphK1, LPAR2, and the three major S1P receptors in 27 colorectal cancer samples and corresponding normal tissue samples. We also examined the correlation between the expression of SphK1 and LPAR2.. Colorectal cancer tissue in 22 of 27 patients had higher levels of SphK1 mRNA than in normal tissue. In two-thirds of the samples, SphK1 mRNA expression was more than two-fold higher than in normal tissue. Consistent with previous reports, LPAR2 mRNA expression in 20 of 27 colorectal cancer tissue samples was higher compared to normal tissue samples. Expression profiles of all three major S1P receptors, S1PR1, S1PR2, and S1PR3, varied without any trend, with no significant difference in expression between cancer and normal tissues. A highly significant positive correlation was found between SphK1 and LPAR2 expression [Pearson's correlation coefficient (r) = 0.784 and P < 0.01]. The mRNA levels of SphK1 and LPAR2 did not correlate with TNM stage.. Our findings suggest that S1P and LPA may play important roles in the development of colorectal cancer via the upregulation of SphK1 and LPAR2, both of which could serve as new therapeutic targets in the treatment of colorectal cancer.

Topics: Adenocarcinoma; Aged; Aged, 80 and over; Colorectal Neoplasms; Female; Gene Expression Regulation, Neoplastic; Humans; Male; Middle Aged; Neoplasm Staging; Phosphotransferases (Alcohol Group Acceptor); Real-Time Polymerase Chain Reaction; Receptors, Lysophosphatidic Acid; Receptors, Lysosphingolipid; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Sphingosine-1-Phosphate Receptors; Up-Regulation

MicroRNAs (miRs) dysregulation is a general feature of colorectal cancer (CRC) and other solid tumors, and is associated cancer progression. In the current study, we demonstrate that microRNA-101 (miR-101) inhibits CRC cells probably through down-regulating sphingosine kinase 1 (SphK1). Our results showed that exogenously expressing miR-101 inhibited CRC cell (HT-29 and HCT-116 lines) growth in vitro. At the molecular level, miR-101 dramatically down-regulated SphK1 mRNA and protein expression, causing pro-apoptotic ceramide production in above CRC cells. On the other hand, inhibition of miR-101 through expressing antagomiR-101 increased SphK1 expression to down-regulate ceramide level in HT-29 cells. miR-101 expression increased the in vitro anti-CRC activity of conventional chemo-agents: paclitaxel and doxorubicin. CRC cells with SphK1-shRNA knockdown showed similar phenotypes as the miR-101-expressed CRC cells, presenting with elevated level of ceramide and high sensitivity to paclitaxel or doxorubicin. In vivo, HCT-116 xenograft growth in severe combined immuno-deficient (SCID) mice was dramatically inhibited by over-expressing miR-101. Further, miR-101 enhanced paclitaxel-induced anti-HCT-116 activity in vivo. Together, these results indicate that miR-101 exerts its anti-CRC activities probably through down-regulating SphK1.

Topics: Animals; Antineoplastic Agents, Phytogenic; Base Sequence; Cell Division; Colorectal Neoplasms; DNA Primers; Down-Regulation; HT29 Cells; Humans; Mice; Mice, SCID; MicroRNAs; Paclitaxel; Phosphotransferases (Alcohol Group Acceptor); Real-Time Polymerase Chain Reaction

Although the anti-EGF receptor (EGFR) monoclonal antibody cetuximab is an effective strategy in colorectal cancer therapy, its clinical use is limited by intrinsic or acquired resistance. Alterations in the "sphingolipid rheostat"-the balance between the proapoptotic molecule ceramide and the mitogenic factor sphingosine-1-phosphate (S1P)-due to sphingosine kinase 1 (SphK1) overactivation have been involved in resistance to anticancer-targeted agents. Moreover, cross-talks between SphK1 and EGFR-dependent signaling pathways have been described.. We investigated SphK1 contribution to cetuximab resistance in colorectal cancer, in preclinical in vitro/in vivo models, and in tumor specimens from patients.. SphK1 was found overexpressed and overactivated in colorectal cancer cells with intrinsic or acquired resistance to cetuximab. SphK1 contribution to resistance was supported by the demonstration that SphK1 inhibition by N,N-dimethyl-sphingosine or silencing via siRNA in resistant cells restores sensitivity to cetuximab, whereas exogenous SphK1 overexpression in sensitive cells confers resistance to these agents. Moreover, treatment of resistant cells with fingolimod (FTY720), a S1P receptor (S1PR) antagonist, resulted in resensitization to cetuximab both in vitro and in vivo, with inhibition of tumor growth, interference with signal transduction, induction of cancer cells apoptosis, and prolongation of mice survival. Finally, a correlation between SphK1 expression and cetuximab response was found in colorectal cancer patients.

Topics: Animals; Antibodies, Monoclonal, Humanized; Antineoplastic Agents; Cell Line, Tumor; Cetuximab; Colorectal Neoplasms; Disease Models, Animal; Drug Resistance, Neoplasm; Fingolimod Hydrochloride; Gene Expression; Humans; Mice; Mice, Nude; Phosphotransferases (Alcohol Group Acceptor); Propylene Glycols; Receptors, Lysosphingolipid; Sphingosine; Sphingosine-1-Phosphate Receptors; Treatment Outcome; Xenograft Model Antitumor Assays

Expression of sphingosine kinase 1 (SPHK1) plays a role in colorectal cancer progression. This study aimed to demonstrate the mechanism of human colorectal cancer cell metastatic phenotype through SPHK1 knockdown. Human colorectal cancer HT-29 cells were stimulated by phorbol 12-myristate 13-acetate (PMA) with or without SPHK1 siRNA transfection. Tumor cell phenotypic changes were analyzed by using invasion, motility, cell viability, and apoptosis assays. Gene expressions were assessed using Western blot. PMA induced a metastatic phenotype in colorectal cancer cells, as indicated by cell viability, migration and invasion capacity, and ERK1/2 phosphorylation, whereas SPHK1 siRNA transfection suppressed the metastatic phenotype of tumor cells and antagonized PMA's effects. SPHK1 knockdown also inhibited secretion of MMP-2 and MMP-9 into the tumor cell conditioned medium. Suppression of SPHK1 expression suppresses the PMA-induced metastatic phenotype via ERK1/2 phosphorylation in human colorectal cancer cells.

Topics: Apoptosis; Blotting, Western; Carcinogens; Cell Adhesion; Cell Movement; Cell Proliferation; Colorectal Neoplasms; Enzyme-Linked Immunosorbent Assay; Humans; Phosphotransferases (Alcohol Group Acceptor); Protein Kinase C; RNA, Small Interfering; Tetradecanoylphorbol Acetate

Overexpression and activation of tyrosine kinase receptors are common features of colorectal cancer. Using the human colorectal cancer cell lines DLD-1 and Caco-2, we evaluated the role of the insulin-like growth factor-I (IGF-I) receptor (IGF-IR) and epidermal growth factor receptor (EGFR) in cellular functions of these cells. We used the small interfering RNA (siRNA) technology to specifically down-regulate IGF-IR and EGFR expression. Knockdown of IGF-IR and EGFR resulted in inhibition of cell proliferation of DLD-1 and Caco-2 cells. An increased rate of apoptosis was associated with siRNA-mediated silencing of IGF-IR and EGFR as assessed by activation of caspase-3/caspase-7. The combined knockdown of both EGFR and IGF-IR decreased cell proliferation and induced cell apoptosis more effectively than did silencing of either receptor alone. Comparable effects on cell proliferation and apoptosis were observed after single and combinational treatment of cells by the IGF-IR tyrosine kinase inhibitor NVP-AEW541 and/or the EGFR tyrosine kinase inhibitor erlotinib. Combined IGF-IR and EGFR silencing by either siRNAs or tyrosine kinase inhibitors diminished the phosphorylation of downstream signaling pathways AKT and extracellular signal-regulated kinase (ERK)-1/2 more effectively than did the single receptor knockdown. Single IGF-IR knockdown inhibited IGF-I-dependent phosphorylation of AKT but had no effect on IGF-I- or EGF-dependent phosphorylation of ERK1/2, indicating a role of EGFR in ligand-dependent ERK1/2 phosphorylation. The present data show that inhibition of the IGF-IR transduction cascade augments the antipoliferative and proapoptotic effects of EGFR inhibition in colorectal cancer cells. A clinical application of combination therapy targeting both EGFR and IGF-IR could be a promising therapeutic strategy.

Topics: Apoptosis; Blotting, Western; Cell Proliferation; Colorectal Neoplasms; ErbB Receptors; Gene Silencing; Humans; Phosphotransferases (Alcohol Group Acceptor); Receptor, IGF Type 1; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; RNA, Small Interfering; Tumor Cells, Cultured