SiRNA-mediated IGF-1R inhibition sensitizes human colon cancer SW480 cells to radiation

Role of non-coding RNAs in radiosensitivity of colorectal cancer: A narrative review

Colorectal cancer (CRC) is a global public health concern because of its high prevalence and mortality. Although radiotherapy is a key method for treating CRC, radioresistance is an obstacle to radiotherapy use. The molecular mechanisms underlying the radioresistance of CRC remain unclear. Increasing evidence has revealed the multiple regulatory functions of non-coding RNAs (ncRNAs) in numerous malignancies, including CRC. Several ncRNAs have been reported to be involved in the determination of radiosensitivity of CRC cells, and some have excellent potential to be prognostic biomarkers or therapeutic targets in CRC treatment. The present review discusses the biological functions and underlying mechanisms of ncRNAs (primarily lncRNA, miRNA, and circRNA) in the regulation of the radiosensitivity of CRC. We also evaluate studies that examined ncRNAs as biomarkers of response to radiation and as therapeutic targets for enhancing radiosensitivity.

DDAB cationic lipid-mPEG, PCL copolymer hybrid nano-carrier synthesis and application for delivery of siRNA targeting IGF-1R into breast cancer cells

BACKGROUND AND OBJECTIVE

To use siRNA molecule as a therapeutic agent in gene silencing, an efficient delivery system is necessary. Stability and clearance by reticuloendothelial of siRNA still remains the major challenges for clinical application. Herein, we could develop new lipid-polymer hybrid nanoparticles (LPHNP) as a siRNA carrier to silence insulin-like growth factor type I (IGF-1R) gene overexpression in MCF-7 human breast cancer cell line.

METHODS

Dimethyldioctadecylammonium bromide-methoxy poly(ethylene glycol)-poly (ε-caprolactone) (DDAB-mPEG-PCL) LPHNPs were synthesized using a single step nanoprecipitation method and characterized by dynamic light scattering (DLS) and atomic force microscopy (AFM) microscope. Cytotoxicity of the nanoparticles was assessed in the MCF7 cell line using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. Desired LPHNP-siRNA complex was determined using different Nitrogen:Phosphate ratio (N/P) ratios and gel retardation. To determine the encapsulation efficiency of siRNA (%) in LPHNP, its absorbance was measured. The effect of the siRNA-LPHNP complex on IGF-1R silencing was assessed by reverse transcription-polymerase chain reaction (RT-PCR) RESULTS: LPHNP was synthesized using a single-step sonication method with a size below 100 nM. The viability of cells treated with hybrid nanoparticles was significantly greater than the corresponding cationic lipid (P < 0.01). As demonstrated by gel retardation assay, efficient siRNA binding to LPHNP occurred at N/P equal to 40 and siRNA encapsulation efficiency was found to be 95% ± 4 at this ratio. LPHNP-IGF-1R siRNA complex could be able to down-regulate the target more efficiently when it compared with the corresponded controls (P < 0.001).

CONCLUSION

In conclusion, our results suggest that DDAB cationic lipid and mPEG-PCL copolymer hybrid nanoparticle may be a good candidate for efficient siRNA delivery.

IGF-1 Receptor Signaling Regulates Type II Pneumocyte Senescence and Resulting Macrophage Polarization in Lung Fibrosis

PURPOSE

Type II pneumocyte (alveolar epithelial cells type II [AECII]) senescence has been implicated in the progression of lung fibrosis. The capacity of senescent cells to modulate pulmonary macrophages to drive fibrosis is unexplored. Insulin-like growth factor-1 receptor (IGF-1R) signaling has been implicated as a regulator of senescence and aging.

METHODS AND MATERIALS

Mice with an AECII-specific deletion of IGF-1R received thoracic irradiation (n ≥ 5 per condition), and the effect of IGF-1R deficiency on radiation-induced AECII senescence and macrophage polarization to an alternatively activated phenotype (M2) was investigated. IGF-1R signaling, macrophage polarization, and senescence were evaluated in surgically resected human lung (n = 63).

RESULTS

IGF-1R deficient mice demonstrated reduced AECII senescence (senescent AECII/field; intact: 7.25% ± 3.5% [mean ± SD], deficient: 2.75% ± 2.8%, P = .0001), reduced accumulation of M2 macrophages (intact: 24.7 ± 2.2 cells/field, deficient: 15.5 ± 1.2 cells/field, P = .0086), and fibrosis (hydroxyproline content; intact: 71.9 ± 21.7 μg/lung, deficient: 31.7 ± 7.9, P = .0485) after irradiation. Senescent AECII enhanced M2 polarization in a paracrine fashion (relative Arg1 mRNA, 0 Gy: 1.0 ± 0.4, 17.5 Gy: 7.34 ± 0.5, P < .0001). Evaluation of surgical samples from patients treated with chemoradiation demonstrated increased expression of IGF-1 (unirradiated: 10.2% ± 4.9% area, irradiated: 15.1% ± 11.5%, P = .0377), p21 (unirradiated: 0.013 ± 0.02 histoscore, irradiated: 0.084 ± 0.09 histoscore, P = .0002), IL-13 (unirradiated: 13.7% ± 2.8% area, irradiated: 21.7% ± 3.8%, P < .0001), and M2 macrophages in fibrotic regions relative to nonfibrotic regions (unirradiated: 11.4 ± 12.2 CD163 + cells/core, irradiated: 43.1 ± 40.9 cells/core, P = .0011), consistent with findings from animal models of lung fibrosis.

CONCLUSIONS

This study demonstrates that senescent AECII are necessary for the progression of pulmonary fibrosis and serve as a targetable, chronic stimuli for macrophage activation in fibrotic lung.

Downregulation of IGF1R Expression Inhibits Growth and Enhances Cisplatin Sensitivity of Head and Neck Squamous Cell Carcinoma Cells In Vitro

A lentivirus-mediated doxycycline-inducible pTRIPZ shRNAmir plasmid targeting IGF1R transcript was transfected into two head and neck squamous cell carcinoma (HNSCC) cell lines to silence IGF1R expression and to assess the effect of its downregulation on cisplatin sensitivity in vitro. In Cal27-regIGF1R and SCC25-regIGF1R cell lines, IGF1R protein expression was reduced by more than 90% after 72 h of incubation with doxycycline. Both basal and IGF-stimulated pIGF1R, pAKT, and pERK were significantly reduced, without influence on total AKT and ERK expression. Downregulation of the IGF1R was associated with decreased proliferation and cell viability in both cell lines. Reduced IGF1R expression was also associated with increased sub-G0/G1-phase and G0/G1-phase populations and decreased S-phase and G2/M-phase populations. IGF1R downregulation enhanced sensitivity to cisplatin with decrease of cisplatin IC₅₀ from 15 to 7.1 in Cal27-regIGF1R cells and from 11 to 6.3 in SCC25-regIGF1R cells. Cisplatin exhibited increased pro-apoptotic activity by annexin V staining and PARP cleavage in both cells lines when cultured in doxycycline. Thus, in two HNSCC cell lines in vitro, reduced IGF1R expression results in reduced growth rate and increased sensitivity to cisplatin. Thus, IGF1R downregulation and/or inhibition may serve as a useful adjunct to platinum-based cytotoxic chemotherapy.

Personalized Radiation Oncology: Epidermal Growth Factor Receptor and Other Receptor Tyrosine Kinase Inhibitors

Molecular biomarkers are currently evaluated in preclinical and clinical studies in order to establish predictors for treatment decisions in radiation oncology. The receptor tyrosine kinases (RTK) are described in the following text. Among them, the most data are available for the epidermal growth factor receptor (EGFR) that plays a major role for prognosis of patients after radiotherapy, but seems also to be involved in mechanisms of radioresistance, specifically in repopulation of tumour cells between radiotherapy fractions. Monoclonal antibodies against the EGFR improve locoregional tumour control and survival when applied during radiotherapy, however, the effects are heterogeneous and biomarkers for patient selection are warranted. Also other RTK´s such as c-Met and IGF-1R seem to play important roles in tumour radioresistance. Beside the potential to select patients for molecular targeting approaches combined with radiotherapy, studies are also needed to evluate radiotherapy adaptation approaches for selected patients, i.e. adaptation of radiation dose, or, more sophisticated, of target volumes.

Evasion of anti-growth signaling: A key step in tumorigenesis and potential target for treatment and prophylaxis by natural compounds

The evasion of anti-growth signaling is an important characteristic of cancer cells. In order to continue to proliferate, cancer cells must somehow uncouple themselves from the many signals that exist to slow down cell growth. Here, we define the anti-growth signaling process, and review several important pathways involved in growth signaling: p53, phosphatase and tensin homolog (PTEN), retinoblastoma protein (Rb), Hippo, growth differentiation factor 15 (GDF15), AT-rich interactive domain 1A (ARID1A), Notch, insulin-like growth factor (IGF), and Krüppel-like factor 5 (KLF5) pathways. Aberrations in these processes in cancer cells involve mutations and thus the suppression of genes that prevent growth, as well as mutation and activation of genes involved in driving cell growth. Using these pathways as examples, we prioritize molecular targets that might be leveraged to promote anti-growth signaling in cancer cells. Interestingly, naturally occurring phytochemicals found in human diets (either singly or as mixtures) may promote anti-growth signaling, and do so without the potentially adverse effects associated with synthetic chemicals. We review examples of naturally occurring phytochemicals that may be applied to prevent cancer by antagonizing growth signaling, and propose one phytochemical for each pathway. These are: epigallocatechin-3-gallate (EGCG) for the Rb pathway, luteolin for p53, curcumin for PTEN, porphyrins for Hippo, genistein for GDF15, resveratrol for ARID1A, withaferin A for Notch and diguelin for the IGF1-receptor pathway. The coordination of anti-growth signaling and natural compound studies will provide insight into the future application of these compounds in the clinical setting.

Demonstration of dose dependent cytotoxic activity in SW480 colon cancer cells by ¹⁷⁷Lu-labeled siRNA targeting IGF-1R

PURPOSE

The radiolabeling of targeting biomolecules with gamma emitter radionuclides for tracing and beta emitters for therapy involves the conjugation of such biomolecules to the chelating agents to form complexes with the radionuclide of interest. In this study, radioconjugate of IGF-1R siRNA with lutetium-177 ((177)Lu) was produced, and the anti-proliferation and apoptosis effects elicited by this (177)Lu-siRNA complex in the SW480 colon cancer cells were evaluated.

METHODS

IGF-1R and Luciferase siRNAs were conjugated with p-SCN-Bn-DTPA, and then radiolabeled with (177)Lu. The effects of labeled and non-labeled IGF-1R siRNAs on IGF-1R expression were assessed with RT-PCR analysis and ELISA assay. IGF-1R siRNAs induced cell death and apoptosis were investigated using MTT assay and Annexin-V/propidium iodide (PI) double staining, respectively.

RESULTS

Combined purification using Vivaspin and PD-10 columns resulted in a radiochemical purity of 97.32% ± 1.97%. Knockdown effect of the labeled IGF-1R siRNA was not significantly different from the non-labeled duplex of the same sequence (P<0.05), but it was significant compared to the Luciferase siRNAs (P<0.001). Proliferation decreased significantly, but apoptosis increased in the cells treated with the (177)Lu-IGF-1R siRNA in comparison with either (177)Lu or IGF-1R siRNA (P<0.001).

CONCLUSION

Radioconjugate of IGF-1R siRNA, p-SCN-Bn-DTPA and (177)Lu was successfully produced and characterized as radiopharmaceutical. The present study demonstrates the involvement of (177)Lu-labeled IGF-1R siRNA in the inhibition of cell growth and induction of apoptosis in colon cancer cells.

IGF1 receptor signaling regulates adaptive radioprotection in glioma stem cells

Cancer stem cells (CSCs) play an important role in disease recurrence after radiation treatment as a result of intrinsic properties such as high DNA repair capability and antioxidative capacity. It is unclear, however, how CSCs further adapt to escape the toxicity of the repeated irradiation regimens used in clinical practice. Here, we have exposed a population of murine glioma stem cells (GSCs) to fractionated radiation in order to investigate the associated adaptive changes, with the ultimate goal of identifying a targetable factor that regulates acquired radioresistance. We have shown that fractionated radiation induces an increase in IGF1 secretion and a gradual upregulation of the IGF type 1 receptor (IGF1R) in GSCs. Interestingly, IGF1R upregulation exerts a dual radioprotective effect. In the resting state, continuous IGF1 stimulation ultimately induces downregulation of Akt/extracellular-signal-regulated kinases (ERK) and FoxO3a activation, which results in slower proliferation and enhanced self-renewal. In contrast, after acute radiation, the abundance of IGF1R and increased secretion of IGF1 promote a rapid shift from a latent state toward activation of Akt survival signaling, protecting GSCs from radiation toxicity. Treatment of tumors formed by the radioresistant GSCs with an IGF1R inhibitor resulted in a marked increase in radiosensitivity, suggesting that blockade of IGF1R signaling is an effective strategy to reverse radioresistance. Together, our results show that GSCs evade the damage of repeated radiation not only through innate properties but also through gradual inducement of resistance pathways and identify the dynamic regulation of GSCs by IGF1R signaling as a novel mechanism of adaptive radioprotection.

A bioinformatics filtering strategy for identifying radiation response biomarker candidates

The number of biomarker candidates is often much larger than the number of clinical patient data points available, which motivates the use of a rational candidate variable filtering methodology. The goal of this paper is to apply such a bioinformatics filtering process to isolate a modest number (<10) of key interacting genes and their associated single nucleotide polymorphisms involved in radiation response, and to ultimately serve as a basis for using clinical datasets to identify new biomarkers. In step 1, we surveyed the literature on genetic and protein correlates to radiation response, in vivo or in vitro, across cellular, animal, and human studies. In step 2, we analyzed two publicly available microarray datasets and identified genes in which mRNA expression changed in response to radiation. Combining results from Step 1 and Step 2, we identified 20 genes that were common to all three sources. As a final step, a curated database of protein interactions was used to generate the most statistically reliable protein interaction network among any subset of the 20 genes resulting from Steps 1 and 2, resulting in identification of a small, tightly interacting network with 7 out of 20 input genes. We further ranked the genes in terms of likely importance, based on their location within the network using a graph-based scoring function. The resulting core interacting network provides an attractive set of genes likely to be important to radiation response.

Role of IGF-1 receptor in radiation response

Insulin-like growth factor 1 receptor (IGF-1R) is a transmembrane receptor tyrosine kinase involved in the development and progression of cancer whose activation strongly promotes cell growth and survival. IGF-1R exerts its main actions through the activation of the mitogen-activated protein kinase and phosphoinositide 3-kinase pathways. In addition to their traditional roles, IGF-1R activation has been associated with increased radioresistance both in vitro and in vivo, although the molecular mechanisms behind this process are still unclear. Recently, IGF-1R has been associated to new partners as major vault proteins, BCL-2, BAX, or Ku70/80, related to radiochemotherapy resistance, regulation of apoptosis, and nonhomologous end-joining DNA repair. Here, we review these novel associations of IGF-1R trying to explain the resistance to radiotherapy mediated by IGF-1R. Finally, we revised the role of new therapies leading to block the receptor to enhance the efficacy of radiation.

IGF-1R expression predicts clinical outcome in patients with locally advanced oral squamous cell carcinoma

To assess the expression of IGF-1R in oral cavity squamous cell carcinoma patients, to explore its relation with clinical and pathologic prognostic factors and its role in predicting clinical outcome. One hundred and thirty-one consecutive patients suffering from oral cavity squamous cell carcinoma were included in this study from July 1989 to April 2005. Follow-up was closed in May 2010. The mean follow-up for survivors was 110.26±47.42 months. Patients were staged following the TNM classification. Patients in tumour stages I and II were referred to surgery. Patients in stages III-IV were referred to postoperative radiotherapy. Radiation therapy was administered up to a mean dose of 62.13±7.74 Gy in 1.8-2 Gy fractions. IGF-1R expression was studied by immunohistochemistry in paraffin-embedded tumour tissue. IGF-1R was expressed in 101 patients (77.1%). IGF-1R expression was related to tumour grade (P=0.012). Tumour stage was the most important prognostic factor for survival. Low (negative and fairly) IGF-1R tumour expression was correlated to better long-term Local Disease Free Survival (P=0.016), Disease-Free Survival (P=0.029), and Survival (P=0.009) in patients achieving tumour stages III-IV. Low IGF-1R expression was related to better long-term control in patients suffering locally advanced oral carcinoma.

A gene expression signature for chemoradiosensitivity of colorectal cancer cells

PURPOSE

The standard treatment of patients with locally advanced rectal cancers comprises preoperative 5-fluorouracil-based chemoradiotherapy followed by standardized surgery. However, tumor response to multimodal treatment has varied greatly, ranging from complete resistance to complete pathologic regression. The prediction of the response is, therefore, an important clinical need.

METHODS AND MATERIALS

To establish in vitro models for studying the molecular basis of this heterogeneous tumor response, we exposed 12 colorectal cancer cell lines to 3 μM of 5-fluorouracil and 2 Gy of radiation. The differences in treatment sensitivity were then correlated with the pretherapeutic gene expression profiles of these cell lines.

RESULTS

We observed a heterogeneous response, with surviving fractions ranging from 0.28 to 0.81, closely recapitulating clinical reality. Using a linear model analysis, we identified 4,796 features whose expression levels correlated significantly with the sensitivity to chemoradiotherapy (Q <.05), including many genes involved in the mitogen-activated protein kinase signaling pathway or cell cycle genes. These data have suggested a potential relevance of the insulin and Wnt signaling pathways for treatment response, and we identified STAT3, RASSF1, DOK3, and ERBB2 as potential therapeutic targets. The microarray measurements were independently validated for a subset of these genes using real-time polymerase chain reactions.

CONCLUSION

We are the first to report a gene expression signature for the in vitro chemoradiosensitivity of colorectal cancer cells. We anticipate that this analysis will unveil molecular biomarkers predictive of the response of rectal cancers to chemoradiotherapy and enable the identification of genes that could serve as targets to sensitize a priori resistant primary tumors.