Ionizing radiation modules of the expression and tyrosine phosphorylation of the focal adhesion‐associated proteins focal adhesion kinase (FAK) and its substrates p130cas and paxillin in A549 human lung carcinoma cellsin vitro

P130cas-FAK interaction is essential for YAP-mediated radioresistance of non-small cell lung cancer

Based on the RNA-sequencing data, previous studies revealed that extracellular matrix receptor interaction and focal adhesion signaling pathways were enriched in radioresistant non-small cell lung cancer (NSCLC) cell lines. As the principal members of these signaling pathways, recent studies showed that FAK controlled YAP's nuclear translocation and activation in response to mechanical activation. However, the underlying mechanisms are largely unknown. This study was designed to determine whether P130cas plays a role in FAK-YAP axis-mediated radioresistance. We found that P130cas promoted proliferation, altered the cell cycle profile, and enhanced tumor growth using cell lines and xenograft mouse models. After treating the cell lines and xenograft models with a single dose of 5 Gy irradiation, we observed that P130cas effectively induced radioresistance in vitro and in vivo. We confirmed that P130cas interacted with and promoted YAP stabilization, thereby facilitating YAP's activation and nuclear translocation and downregulating the radiosensitivity of NSCLC. Our data also revealed that P130cas and FAK directly interacted with each other and worked together to regulate YAP's activation and nuclear translocation. Furthermore, the present study identified that P130cas, FAK and YAP formed a triple complex to induce radioresistance. Using P130cas-ΔSH3, FAK- P712/715A mutant, YAP-ΔSH3bm and YAP-ΔWW mutant, our results showed that targeting P130cas-FAK interaction may be a more cost-effective way to overcome the YAP activation mediated radioresistance in NSCLC. Using the data of the public database and our clinical samples, the present study suggested that the expression of P130cas correlated with YAP expression and indicated a poor overall response rate of NSCLC patients who underwent radiation therapy. Overall, our study extends the knowledge of FAK-YAP interaction and provides new insight into understanding the underlying mechanisms to overcome the radioresistance of NSCLC.

Focal adhesion kinase: Insight into its roles and therapeutic potential in oesophageal cancer

Oesophageal cancer is associated with high morbidity and mortality rates because it is highly invasive and prone to recurrence and metastasis, with a five-year survival rate of <20%. Therefore, there is an urgent need for new methods aimed at improving therapeutic intervention. Several studies have shown that targeted therapy may be effective for the treatment of oesophageal cancer. Focal adhesion kinase (FAK), a non-receptor tyrosine kinase with kinase activity and scaffolding function, could be overexpressed in a variety of solid tumours, including oesophageal cancer. FAK participates in survival, proliferation, progression, adhesion, invasion, migration, epithelial-to-mesenchymal transition, angiogenesis, DNA damage repair, and other biological processes through multiple signalling pathways in cancer cells. It plays an important role in the occurrence and development of tumours and has been linked to the prognosis of oesophageal cancer. FAK has been suggested as a potential therapeutic target in oesophageal cancer; thus, the combination of FAK inhibitors with chemotherapy, radiotherapy, and immunotherapy is expected to prolong the survival of patients. This paper presents a brief overview of the structure of FAK and its potential role in oesophageal cancer, providing a rationale for the future application of FAK inhibitors in the treatment of the disease.

Association between breast cancer cell migration and radiosensitivity in vitro

The aim of the present study was to examine the association between the migration of breast cancer cells in vitro and radiosensitivity by establishing a breast cancer cell model with different migratory capacities. Transwell chambers in a 24-well plate were used to separate MDA-MB-231 and ZR-7530 cells and to establish cell models with different migratory capacities. Subsequently, the radiosensitivity of the cell models was measured using a radiation clone formation assay. Furthermore, differential gene expression was determined using gene microarray analysis. The protein expression levels of the differentially expressed genes (DEGs) were assessed using western blot analysis. From each parental cell line, a pair of daughter cell lines were established in with differing migratory abilities. These daughter cell lines were named MDA-MB-231 UP-10 (231 UP-10), MDA-MB-231 Down-10 (231 Down-10), ZR-75-30 UP-10 (7530 UP-10) and ZR-75-30 Down-10 (7530 Down-10). Radiation clone formation assays revealed that the cell lines with increased migratory abilities (231 Down-10 and 7530 Down-10) demonstrated higher radio-resistance compared with the cell lines with decreased migratory abilities (231 UP-10 and 7530 UP-10). Gene microarrays identified numerous DEGs between the pairs of UP and Down cell lines. A focus was placed on genes associated with cell adhesion and it was identified that phosphorylated Fak and phosphorylated EGFR expression levels were increased in 231 Down-10 and 7530 Down-10 cells, compared with the 231 UP-10 and 7530 UP-10 cells. Other genes including ZO-1, FN1 and SOX9 expression were also increased in the 231 Down-10 and 7530 Down-10 cells compared with 231 UP-10 and 7530 UP-10 cells. Cell lines with increased migratory capacities may be more radio-resistant compared with cell lines with a decreased migratory capabilities. The mechanism may be associated with changes in the expression of cell adhesion molecules and epithelial-mesenchymal transition (EMT). Therapeutic strategies targeting cell adhesion or EMT may increase the radiation sensitivity of breast cancer cells, in addition to improving the effect of radiation therapy.

Role of Focal Adhesion Kinase in Small-Cell Lung Cancer and Its Potential as a Therapeutic Target

Small-cell lung cancer (SCLC) represents 15% of all lung cancers and it is clinically the most aggressive type, being characterized by a tendency for early metastasis, with two-thirds of the patients diagnosed with an extensive stage (ES) disease and a five-year overall survival (OS) as low as 5%. There are still no effective targeted therapies in SCLC despite improved understanding of the molecular steps leading to SCLC development and progression these last years. After four decades, the only modest improvement in OS of patients suffering from ES-SCLC has recently been shown in a trial combining atezolizumab, an anti-PD-L1 immune checkpoint inhibitor, with carboplatin and etoposide, chemotherapy agents. This highlights the need to pursue research efforts in this field. Focal adhesion kinase (FAK) is a non-receptor protein tyrosine kinase that is overexpressed and activated in several cancers, including SCLC, and contributing to cancer progression and metastasis through its important role in cell proliferation, survival, adhesion, spreading, migration, and invasion. FAK also plays a role in tumor immune evasion, epithelial-mesenchymal transition, DNA damage repair, radioresistance, and regulation of cancer stem cells. FAK is of particular interest in SCLC, being known for its aggressiveness. The inhibition of FAK in SCLC cell lines demonstrated significative decrease in cell proliferation, invasion, and migration, and induced cell cycle arrest and apoptosis. In this review, we will focus on the role of FAK in cancer cells and their microenvironment, and its potential as a therapeutic target in SCLC.

Identification of potential genes and pathways for response prediction of neoadjuvant chemoradiotherapy in patients with rectal cancer by systemic biological analysis

Currently, neoadjuvant chemoradiotherapy (CRT) followed by radical surgery is the standard of care for locally advanced rectal cancer. However, to the best of our knowledge, there are no effective biomarkers for predicting patients who may benefit from neoadjuvant treatment. The aim of the current study was to screen potential crucial genes and pathways associated with the response to CRT in rectal cancer, and provide valid biological information to assist further investigation of CRT optimization. In the current study, differentially expressed (DE) genes were identified from the tumor samples of responders and non-responders to neoadjuvant CRT in the GSE35452 gene expression profile. Seven hub genes and one significant module were identified from the protein-protein interaction (PPI) network. Functional enrichment analysis of all the DE genes and the hub genes, retrieved from PPI network analysis, revealed their associations with CRT response. Genes were identified that may be used to discriminate patients who would or would not clinically benefit from neoadjuvant CRT. Several important pathways enriched by the DE genes, hub genes and selected module were identified, and revealed to be closely associated with radiation response, including excision repair, homologous recombination, Ras signaling pathway, the forkhead box O signaling pathway, focal adhesion and the Wnt signaling pathway. In conclusion, the current study demonstrated that the identified gene signatures and pathways may be used as molecular biomarkers for predicting CRT response. Furthermore, combinations of these biomarkers may be helpful for optimizing CRT treatment and promoting understanding of the molecular basis of response differences; this needs to be confirmed by further experiments.

FAK alleviates radiation-induced rectal injury by decreasing apoptosis

Radiation-induced rectal injury is closely related with radiotherapy efficiency. Here, we investigated the effect of focal adhesion kinase (FAK) in radiation-induced rectal injury. Peripheral blood samples of patients with rectal cancer were collected prior to radiotherapy. Differentially expressed genes and copy number variations (CNVs) were analyzed by microarray analysis. The CTCAE v3.0 toxicity grades were used to assess acute rectal injury. The radiosensitivity of human intestinal epithelial crypt (HIEC) cells were assayed by colony formation, mitochondrial membrane potential, flow cytometry and western blotting. The rectums of C57BL/6 mice were X-irradiated locally with a single dose of 15 Gy. The effect of FAK on radiation-induced injury was investigated by hematoxylin-eosin (H&E) staining, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL), immunohistochemistry (IHC) and quantitative real-time PCR (qRT-PCR). FAK mRNA level was inversely correlated with rectal injury severity in patient samples. A CNV amplification located on chromosome 8 was closely related with FAK. Further functional assays revealed increased levels of γH2AX expression and apoptosis-related proteins in FAK-silenced HIEC cells. The ratio of TUNEL, cl-caspase-3, cyto-c and bax/bcl-2 expression in the rectum mucosa treated with a FAK inhibitor increased significantly. These results demonstrated that FAK reduced radiation-induced rectal injury by decreasing apoptosis.

Targeting focal adhesion kinase overcomes erlotinib resistance in smoke induced lung cancer by altering phosphorylation of epidermal growth factor receptor

EGFR-based targeted therapies have shown limited success in smokers. Identification of alternate signaling mechanism(s) leading to TKI resistance in smokers is critically important. We observed increased resistance to erlotinib in H358 NSCLC (non-small cell lung carcinoma) cells chronically exposed to cigarette smoke (H358-S) compared to parental cells. SILAC-based mass-spectrometry approach was used to study altered signaling in H358-S cell line. Importantly, among the top phosphosites in H358-S cells we observed hyperphosphorylation of EGFR (Y1197) and non-receptor tyrosine kinase FAK (Y576/577). Supporting these observations, a transcriptomic-based pathway activation analysis of TCGA NSCLC datasets revealed that FAK and EGFR internalization pathways were significantly upregulated in smoking patients, compared to the never-smokers and were associated with elevated PI3K signaling and lower level of caspase cascade and E-cadherin pathways activation. We show that inhibition of FAK led to decreased cellular proliferation and invasive ability of the smoke-exposed cells, and restored their dependency on EGFR signaling. Our data suggests that activation of focal adhesion pathway significantly contributes to erlotinib resistance, and that FAK is a potential therapeutic target for management of erlotinib resistance in smoke-induced NSCLC.

Calpain2 mediates Rab5-driven focal adhesion disassembly and cell migration

The early endosome protein Rab5 was recently shown to promote cell migration by enhancing focal adhesion disassembly through mechanisms that remain elusive. Focal adhesion disassembly is associated to proteolysis of talin, in a process that requires calpain2. Since calpain2 has been found at vesicles and endosomal compartments, we hypothesized that Rab5 stimulates calpain2 activity, leading to enhanced focal adhesion disassembly in migrating cells. We observed that calpain2 co-localizes with EEA1-positive early endosomes and co-immunoprecipitates with EEA1 and Rab5 in A549 lung carcinoma cells undergoing spreading, whereas Rab5 knock-down decreased the accumulation of calpain2 at early endosomal-enriched fractions. In addition, Rab5 silencing decreased calpain2 activity, as shown by cleavage of the fluorogenic substrate tBOC-LM-CMAC and the endogenous substrate talin. Accordingly, Rab5 promoted focal adhesion disassembly in a calpain2-dependent manner, as expression of GFP-Rab5 accelerated focal adhesion disassembly in nocodazole-synchronized cells, whereas pharmacological inhibition of calpain2 with N-acetyl-Leu-Leu-Met prevented both focal adhesion disassembly and cell migration induced by Rab5. In summary, these data uncover Rab5 as a novel regulator of calpain2 activity and focal adhesion proteolysis leading to cell migration.

Focal exposure of limited lung volumes to high-dose irradiation down-regulated organ development-related functions and up-regulated the immune response in mouse pulmonary tissues

Background

Despite the emergence of stereotactic body radiotherapy (SBRT) for treatment of medically inoperable early-stage non-small-cell lung cancer patients, the molecular effects of focal exposure of limited lung volumes to high-dose radiation have not been fully characterized. This study was designed to identify molecular changes induced by focal high-dose irradiation using a mouse model of SBRT.

Results

Central areas of the mouse left lung were focally-irradiated (3 mm in diameter) with a single high-dose of radiation (90 Gy). Temporal changes in gene expression in the irradiated and non-irradiated neighboring lung regions were analyzed by microarray. For comparison, the long-term effect (12 months) of 20 Gy radiation on a diffuse region of lung was also measured. The majority of genes were down-regulated in the focally-irradiated lung areas at 2 to 3 weeks after irradiation. This pattern of gene expression was clearly different than gene expression in the diffuse region of lungs exposed to low-dose radiation. Ontological and pathway analyses indicated these down-regulated genes were mainly associated with organ development. Although the number was small, genes that were up-regulated after focal irradiation were associated with immune-related functions. The temporal patterns of gene expression and the associated biological functions were also similar in non-irradiated neighboring lung regions, although statistical significance was greatly reduced when compared with those from focally-irradiated areas of the lung. From network analysis of temporally regulated genes, we identified inter-related modules associated with diverse functions, including organ development and the immune response, in both the focally-irradiated regions and non-irradiated neighboring lung regions.

Conclusions

Focal exposure of lung tissue to high-dose radiation induced expression of genes associated with organ development and the immune response. This pattern of gene expression was also observed in non-irradiated neighboring areas of lung tissue, indicating a global lung response to focal high-dose irradiation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-016-0338-9) contains supplementary material, which is available to authorized users.

Lysyl oxidase mediates hypoxia-induced radioresistance in non-small cell lung cancer A549 cells

Hypoxia-induced radioresistance has been well known as the main obstacle in cancer radiotherapy. Lysyl oxidase (LOX) was previously demonstrated to play an important role in hypoxia-induced biological behaviors, such as metastasis and angiogenesis, through hypoxia-inducible factor-1α (HIF-1α), which is an important contributing factor to radioresistance in tumor cells. However, how LOX plays a role in hypoxia-induced radioresistance has yet to be determined. Here, we found that LOX expression was in accordance with HIF-1α expression, and LOX expression at the mRNA and protein level, and enzymatic activity were remarkably upregulated in the hypoxic A549 cells, compared with normoxic A549 cells. Inhibition of LOX resulted in the reduction of the ability to repair double-stranded breaks (DSBs), promotion of apoptosis, relief of G2/M cycle arrest, and eventually reduction of hypoxia-induced radioresistance in the hypoxic A549 cells. This suggests that LOX may play an important role in hypoxia-induced radioresistance. Together, our results might suggest a novel potential therapeutic target in the management of non-small cell lung cancer (NSCLC).

Novel anticancer agent, SQAP, binds to focal adhesion kinase and modulates its activity

SQAP is a novel and promising anticancer agent that was obtained by structural modifications from a natural compound. SQAP inhibits angiogenesis in vivo resulting in increased hypoxia and reduced tumor volume. In this study, the mechanism by which SQAP modifies the tumor microenvironment was revealed through the application of a T7 phage display screening. This approach identified five SQAP-binding proteins including sterol carrier protein 2, multifunctional enzyme type 2, proteasomal ubiquitin receptor, UV excision repair protein and focal adhesion kinase (FAK). All the interactions were confirmed by surface plasmon resonance analysis. Since FAK plays an important role in cell turnover and angiogenesis, the influence of SQAP on FAK was the principal goal of this study. SQAP decreased FAK phosphorylation and cell migration in human umbilical vein endothelial cells and A549 cancer cells. These findings suggest that inhibition of FAK phosphorylation works as the mechanism for the anti-angiogenesis activity of SQAP.

Focal adhesion kinase and Wnt signaling regulate human ductal carcinoma in situ stem cell activity and response to radiotherapy

Cancer stem cells (CSCs) can avoid or efficiently repair DNA damage from radio and chemotherapy, which suggests they play a role in disease recurrence. Twenty percentage of patients treated with surgery and radiotherapy for ductal carcinoma in situ (DCIS) of the breast recur and our previous data show that high grade DCIS have increased numbers of CSCs. Here, we investigate the role of focal adhesion kinase (FAK) and Wnt pathways in DCIS stem cells and their capacity to survive irradiation. Using DCIS cell lines and patient samples, we demonstrate that CSC-enriched populations are relatively radioresistant and possess high FAK activity. Immunohistochemical studies of active FAK in DCIS tissue show high expression was associated with a shorter median time to recurrence. Treatment with a FAK inhibitor or FAK siRNA in nonadherent and three-dimensional matrigel culture reduced mammosphere formation, and potentiated the effect of 2 Gy irradiation. Moreover, inhibition of FAK in vitro and in vivo decreased self-renewal capacity, levels of Wnt3a and B-Catenin revealing a novel FAK-Wnt axis regulating DCIS stem cell activity. Overall, these data establish that the FAK-Wnt axis is a promising target to eradicate self-renewal capacity and progression of human breast cancers.

Modulation of radiation injury response in retinal endothelial cells by quinic acid derivative KZ-41 involves p38 MAPK

Radiation-induced damage to the retina triggers leukostasis, retinal endothelial cell (REC) death, and subsequent hypoxia. Resultant ischemia leads to visual loss and compensatory retinal neovascularization (RNV). Using human RECs, we demonstrated that radiation induced leukocyte adhesion through mechanisms involving p38MAPK, p53, and ICAM-1 activation. Additional phenotypic changes included p38MAPK-dependent tyrosine phosphorylation of the focal adhesion scaffolding protein, paxillin (Tyr118). The quinic acid derivative KZ-41 lessened leukocyte adhesion and paxillin-dependent proliferation via inhibition of p38MAPK-p53-ICAM-1 signaling. Using the murine oxygen-induced retinopathy (OIR) model, we examined the effect of KZ-41 on pathologic RNV. Daily ocular application of a KZ-41-loaded nanoemulsion significantly reduced both the avascular and neovascular areas in harvested retinal flat mounts when compared to the contralateral eye receiving vehicle alone. Our data highlight the potential benefit of KZ-41 in reducing both the retinal ischemia and neovascularization provoked by genotoxic insults. Further research into how quinic acid derivatives target and mitigate inflammation is needed to fully appreciate their therapeutic potential for the treatment of inflammatory retinal vasculopathies.

FAK deletion promotes p53-mediated induction of p21, DNA-damage responses and radio-resistance in advanced squamous cancer cells

Focal adhesion kinase (FAK) is a cytoplasmic tyrosine kinase that is elevated in a variety of human cancers. While FAK is implicated in many cellular processes that are perturbed in cancer, including proliferation, actin and adhesion dynamics, polarisation and invasion, there is only some limited information regarding the role of FAK in radiation survival. We have evaluated whether FAK is a general radio-sensitising target, as has been suggested by previous reports. We used a clean genetic system in which FAK was deleted from mouse squamous cell carcinoma (SCC) cells (FAK -/-), and reconstituted with exogenous FAK wild type (wt). Surprisingly, the absence of FAK was associated with increased radio-resistance in advanced SCC cells. FAK re-expression inhibited p53-mediated transcriptional up-regulation of p21, and a sub-set of other p53 target genes involved in DNA repair, after treatment with ionizing radiation. Moreover, p21 depletion promoted radio-sensitisation, implying that FAK-mediated inhibition of p21 induction is responsible for the relative radio-sensitivity of FAK-proficient SCC cells. Our work adds to a growing body of evidence that there is a close functional relationship between integrin/FAK signalling and the p53/p21 pathway, but demonstrates that FAK's role in survival after stress is context-dependent, at least in cancer cells. We suggest that there should be caution when considering inhibiting FAK in combination with radiation, as this may not always be clinically advantageous.

Breast cancer anti-estrogen resistance protein 1 (BCAR1/p130cas) in pulmonary disease tissue and serum

OBJECTIVE

The purpose of the study was to evaluate clinical presentation of breast cancer anti-estrogen resistance protein 1 (BCAR1, also known as p130cas) expression in pulmonary diseases, and to assess its potential as a molecular marker for diagnosis and prognosis.

METHODS

Between March 2008 and August 2010, we enrolled a total of 80 patients (group A) with non-small-cell lung cancer (NSCLC), 48 patients (group B) with pulmonary tuberculosis (including 27 cases of tuberculoma and 21 cases of cavitary pulmonary tuberculosis), and 32 patients (group C) with other benign pulmonary mass (hamartoma in 15 cases, inflammatory pseudotumor in 10 cases, fibroid tumor in 7 cases). Additionally, 160 healthy age- and sex-matched volunteers were recruited as healthy controls. Tissue BCAR1 expression was investigated by using tissue microarray and immunohistochemistry. BCAR1 and tumor markers (carcinoma embryonic antigen [CEA] and the cancer antigens CA19-9 and CA125) in serum were assayed by using ELISA and immunoradiometrics, respectively.

RESULTS

BCAR1 expression was detected (either in the nucleus, the cytoplasm, or both) in tumor cells in 79 of the 80 NSCLC cases in group A, and in fibroblasts in 41 of the 48 pulmonary tuberculosis cases in group B. However, it was not detected in the normal adjacent tissue in 70 of the 80 cases in group A and in 47 of the 48 cases in group B. In group C, BCAR1 expression was negative in all 32 cases. Additionally, we investigated adjacent tissue with acute or chronic inflammation in 20 cases from group C, and found no expression of BCAR1. Serum BCAR1 levels were significantly higher in patients with NSCLC than in the control group, increased gradually with the progression of tumor staging, and decreased after removal of the tumors. The levels were significantly lower in bronchioloalveolar carcinoma than in other subtypes of carcinoma (Mann-Whitney U test, Z = -5.089; p < 0.001). Serum BCAR1 levels were significantly higher in patients with pulmonary tuberculosis than in the control group, were positively and significantly correlated with the diameter of the tuberculosis lesion (Spearman's rho, correlation coefficient 0.753; p < 0.001), and decreased after removal of the tuberculosis lesions. The levels were significantly higher in patients with cavitary pulmonary tuberculosis than in those with tuberculoma (517.6 ± 326.5 vs 282.2 ± 137.6; Student's t-test, t = -3.387; p = 0.001). In group C, there was no appreciable difference in serum BCAR1 levels compared with the matched controls (222.8 ± 111.0 vs 201.6 ± 35.7; Dunnett's T3 test, p = 0.993). The discrimination power of combining BCAR1 and tumor markers in NSCLC versus benign lung diseases was higher than that of sole use of BCAR1 as a marker (maximal sum of sensitivity and specificity: 1.538 vs 1.237).

CONCLUSION

We conclude that a combined assay of serum BCAR1 and traditional tumor markers is potentially applicable for distinguishing NSCLC from benign lung diseases. However, the clinical utility of serum BCAR1 as a molecular marker for prognosis in NSCLC or pulmonary tuberculosis requires further clarification and verification.

Dual targeting of EGFR and focal adhesion kinase in 3D grown HNSCC cell cultures

PURPOSE

Epidermal growth factor receptor (EGFR) and focal adhesion kinase (FAK) show frequent overexpression and hyperactivity in various human malignancies including head and neck squamous cell carcinomas (HNSCC). To examine effects of dual EGFR/FAK inhibition on cellular radiosensitivity of HNSCC cells in a more physiological environment, we employed a previously established laminin-rich extracellular matrix (lrECM) based three-dimensional (3D) cell culture model.

MATERIALS AND METHODS

UTSCC15 and SAS HNSCC cell lines stably transfected with EGFR-CFP or CFP were used. Single or combined EGFR (Cetuximab, siRNA) and FAK (TAE226, siRNA) inhibition were accomplished prior to measuring clonogenic survival and protein expression and phosphorylation. Immunofluorescence enabled visualization of EGFR-CFP and FAK.

RESULTS

Cetuximab resulted in higher radiosensitization in EGFR-CFP overexpressing cell lines than CFP controls. Single EGFR or FAK inhibition mediated radiosensitization, while dual EGFR/FAK targeting further augmented this effect. Despite signaling alterations upon Cetuximab and siRNA knockdown, analysis of protein expression and phosphorylation indicates EGFR and FAK signaling coexistence without obvious overlap.

CONCLUSIONS

Combined EGFR/FAK targeting yielded stronger radiosensitization than either approach alone, which might be based on non-overlapping downstream signaling. Whether dual targeting of EGFR and FAK can reasonably be combined with radiotherapy and chemotherapy needs clarification.

Influence of stress on extracellular matrix and integrin biology

Dynamic interactions between cells and extracellular matrix (ECM) through integrins influence most cellular functions. Normal cells, but even more, tumor cells are subjected to different forms of stress, including ischemia, radical oxygen species production, starvation, mechanical stress or genotoxic insults due to anti-cancer drugs or irradiation. In these situations, an adaptative cellular response occurs, integrating a complex network of intracellular signaling modules, which, depending on stress intensity, may result to either damage repair followed by complete restitution of cellular functions, or programmed cell death. Because of its implication in oncogenesis and anti-cancer therapy, cellular stress response has been thoroughly investigated. However, most of these studies have been performed in the context of isolated cells without taking into consideration that most cells are part of the tissue within which they interact with ECM through integrin. Few studies have described the influence of stress on cell-to-ECM interaction. However, one can speculate that, in these conditions, cells could functionally interact with protein microenvironment either to create positive interactions to survive (for example by facilitating protective pathways) or negative interaction to die (for example by facilitating detachment). In this review, we summarize the knowledge relative to the influence of different stress modalities on ECM remodeling, integrin expression and/or function modifications, and possible functional consequences, independently from the cellular model as these findings came from a large variety of cells (mesenchymal, endothelial, muscular, epithelial and glandular) and fields of application (cancer, vascular biology and tissue engineering). Most studies support the general notion that non-lethal stress favors ECM stiffness, integrin activation and enhanced survival. This field opens large perspectives not only in tumor biology but also in anti-cancer therapy by targeting one or several steps of the integrin-mediated signaling pathway, including integrin ligation, or activation of integrin-linked enzymes or integrin adaptors.

The role of the focal adhesion protein PINCH1 for the radiosensitivity of adhesion and suspension cell cultures

Focal adhesion (FA) signaling mediated by adhesion to extracellular matrix and growth factor receptors contributes to the regulation of the cellular stress response to external stimuli. Critical to focal adhesion assembly and signaling is the adapter protein PINCH1. To evaluate whether the prosurvival function of PINCH1 in radiation cell survival depends on cell adhesion, we examined PINCH1^fl/fl and PINCH1^−/− mouse embryonic fibroblasts and human cancer cell lines. Here, we found that the enhanced cellular radiosensitivity mediated by PINCH1 depletion observed under adhesion conditions is conserved when cells are irradiated under suspension conditions. This unsuspected finding could not be explained by the observed modification of adhesion and growth factor associated signaling involving FAK, Paxillin, p130^CAS, Src, AKT, GSK3β and ERK1/2 under suspension and serum withdrawal relative to adhesion conditions with serum. Our data suggest that the adapter protein PINCH1 critically participates in the regulation of the cellular radiosensitivity of normal and malignant cells similarly under adhesion and suspension conditions.

CAS proteins in normal and pathological cell growth control

Proteins of the CAS (Crk-associated substrate) family (BCAR1/p130Cas, NEDD9/HEF1/Cas-L, EFS/SIN and CASS4/HEPL) are integral players in normal and pathological cell biology. CAS proteins act as scaffolds to regulate protein complexes controlling migration and chemotaxis, apoptosis, cell cycle, and differentiation, and have more recently been linked to a role in progenitor cell function. Reflecting these complex functions, over-expression of CAS proteins has now been strongly linked to poor prognosis and increased metastasis in cancer, as well as resistance to first-line chemotherapeutics in multiple tumor types including breast and lung cancers, glioblastoma, and melanoma. Further, CAS proteins have also been linked to additional pathological conditions including inflammatory disorders, Alzheimer's and Parkinson's disease, as well as developmental defects. This review will explore the roles of the CAS proteins in normal and pathological states in the context of the many mechanistic insights into CAS protein function that have emerged in the past decade.

3D cell cultures of human head and neck squamous cell carcinoma cells are radiosensitized by the focal adhesion kinase inhibitor TAE226

BACKGROUND AND PURPOSE

Focal adhesion kinase (FAK), a main player in integrin signaling and survival, is frequently overexpressed in human cancers and therefore postulated as potential target in cancer therapy. The aim of this study was to evaluate the radiosensitizing potential of the FAK inhibitor TAE226 in three-dimensional (3D) tumor cell cultures.

MATERIALS AND METHODS

Head and neck squamous cell carcinoma (HNSCC) cells (FaDu, UT-SCC15, UT-SCC45), lung cancer cells (A549), colorectal carcinoma cells (DLD-1, HCT-116) and pancreatic tumor cells (MiaPaCa2, Panc1) were treated with different concentrations of TAE226 (0-1mum; 1 or 24h) without or in combination with irradiation (0-6Gy, X-ray, single dose). Subsequently, 3D clonogenic survival assays (laminin-rich extracellular matrix) and Western blotting (expression/phosphorylation, e.g. FAK, Akt, ERK1/2) were performed.

RESULTS

All investigated 3D cell cultures showed a dose-dependent reduction in clonogenic survival by TAE226. Intriguingly, TAE226 only significantly radiosensitized 3D HNSCC cell cultures accompanied by a pronounced dephosphorylation of FAK, Akt and ERK1/2.

CONCLUSIONS

Our data demonstrate TAE226 as potent FAK inhibitor that enhances the cellular radiosensitivity particularly of HNSCC cells grown in a 3D cell culture model. Future in vitro and in vivo investigations will clarify, to which extent this approach might be clinically relevant for radiotherapy of HNSCC.

Candidate protein biodosimeters of human exposure to ionizing radiation

PURPOSE

To conduct a literature review of candidate protein biomarkers for individual radiation biodosimetry of exposure to ionizing radiation.

MATERIALS AND METHODS

Reviewed approximately 300 publications (1973 - April 2006) that reported protein effects in mammalian systems after either in vivo or in vitro radiation exposure.

RESULTS

We found 261 radiation-responsive proteins including 173 human proteins. Most of the studies used high doses of ionizing radiation (>4 Gy) and had no information on dose- or time-responses. The majority of the proteins showed increased amounts or changes in phosphorylation states within 24 h after exposure (range: 1.5- to 10-fold). Of the 47 proteins that are responsive at doses of 1 Gy and below, 6 showed phosphorylation changes at doses below 10 cGy. Proteins were assigned to 9 groups based on consistency of response across species, dose- and time-response information and known role in the radiation damage response.

CONCLUSIONS

ATM (Ataxia telengiectasia mutated), H2AX (histone 2AX), CDKN1A (Cyclin-dependent kinase inhibitor 1A), and TP53 (tumor protein 53) are top candidate radiation protein biomarkers. Furthermore, we recommend a panel of protein biomarkers, each with different dose and time optima, to improve individual radiation biodosimetry for discriminating between low-, moderate-, and high-dose exposures. Our findings have applications for early triage and follow-up medical assessments.

Protein phosphorylation in irradiated human melanoma cells

In the present study, we examined the response of confluent, primary human fibroblasts and cells of a melanoma (YUSAC2) cell line to ionizing radiation mediated through post-translational protein phosphorylation. Since the purpose of our study was to identify novel radiation-induced phosphoproteins in the DNA damage stress response of melanoma cells, we were primarily interested in changes in protein phosphoserine expression at early times after irradiation. Our rationale was that by examining the overall protein phosphorylation profile (the phosphoproteome) in irradiated cells, we might discover novel radiation-induced phosphoproteins that distinguish fibroblasts from melanoma cells. Cell proteins were separated by gel electrophoresis and phosphoproteins were identified by Western blot analysis using nonspecific anti-phosphoamino acid antibodies. This approach was not pursued previously since adequate antibodies for examining global protein phosphoserine expression were unavailable. While some radiation-induced phosphoprotein changes in high-abundance proteins were identified, in general the sensitivity of this approach was not sufficient to detect changes in low-abundance, regulatory proteins. Characterization of these phosphoproteins will require greater enrichment of low-abundance proteins.

Focal adhesion kinase: a promising target for anticancer therapy

Focal adhesion kinase (FAK) is a protein tyrosine kinase acting as an early modulator of the integrin signalling cascade, thus regulating various basic cellular functions. In transformed cells, upregulation of FAK protein expression and uncontroled signalling were held responsible for the promotion of malignant phenotypic characteristics, as well as resistance to chemotherapy and radiotherapy. Direct FAK targeting resulted in the inhibition of the malignant phenotype of cancer cells, whereas increased apoptotic rates of cancer cells, either used alone or in combination with conventional chemotherapeutic agents, radiotherapy or hormonal therapy. Furthermore, drugs used in cancer chemotherapy, besides their basic mode of action, were also shown to act through altering FAK signalling. Finally, positive results were noted by the transfection of cancer cells with fak mutants or genes that suppress FAK expression or activity, such as phosphatase and tensin homolog deleted on chromosome Ten (PTEN), ribonucleotide reductase M1 polypeptide (RRM1) and melanoma differentiation-associated gene-7 (mda-7). The purpose of this article is a comprehensive review of the existing data on the possible use of FAK targeting in anticancer therapy.

Adhesion molecules in radiotherapy

Recent studies have documented changes in adhesion molecule expression and function after exposure to ionizing radiation. Adhesion molecules mediate cell-cell and cell-matrix interactions and are essential for a variety of physiological and pathological processes including maintenance of normal tissue integrity as well as tumor development and progression. Consequently, modulation of adhesion molecules by radiation may have a role in radiation-induced tumor control and normal tissue damage by interfering with cell signaling, radioresistance, metastasis, angiogenesis, carcinogenesis, immune response, inflammation and fibrosis. In addition, the interactions of radiation with adhesion molecules could have a major impact in developing new strategies to increase the efficacy of radiation therapy. Remarkable progress has been made in recent years to design targeted drug delivery to radiation-up-regulated adhesion molecules. Furthermore, the inhibition of adhesion, migration, invasion and angiogenesis by blocking adhesion receptors may represent a new therapeutic approach to improve tumor control and decrease radiation toxicity. This review is focused on current data concerning the mechanistic interactions of radiation with adhesion molecules and the possible clinical-pathological implications in radiotherapy.

Signalling via integrins: implications for cell survival and anticancer strategies

Integrin-associated signalling renders cells more resistant to genotoxic anti-cancer agents like ionizing radiation and chemotherapeutic substances, a phenomenon termed cell adhesion-mediated radioresistance/drug resistance (CAM-RR, CAM-DR). Integrins are heterodimeric cell-surface molecules that on one side link the actin cytoskeleton to the cell membrane and on the other side mediate cell-matrix interactions. In addition to their structural functions, integrins mediate signalling from the extracellular space into the cell through integrin-associated signalling and adaptor molecules such as FAK (focal adhesion kinase), ILK (integrin-linked kinase), PINCH (particularly interesting new cysteine-histidine rich protein) and Nck2 (non-catalytic (region of) tyrosine kinase adaptor protein 2). Via these molecules, integrin signalling tightly and cooperatively interacts with receptor tyrosine kinase signalling to regulate survival, proliferation and cell shape as well as polarity, adhesion, migration and differentiation. In tumour cells of diverse origin like breast, colon or skin, the function and regulation of these molecules is partly disturbed and thus might contribute to the malignant phenotype and pre-existent and acquired multidrug resistance. These issues as well as a variety of therapeutic options envisioned to influence tumour cell growth, metastasis and resistance, including kinase inhibitors, anti-integrin antibodies or RNA interference, will be summarized and discussed in this review.

Integrin-mediated cell–matrix interactions for prosurvival and antiapoptotic signaling after genotoxic injury

Interactions of cells with their microenvironment modify the cellular sensitivity of normal and tumor cells for radiation- and drug-induced genotoxic injury. The preexistent or acquired cellular resistance against such agents aggravates anticancer therapies and, therefore, complicates the recovery of patients. Recently, integrin-mediated adhesion was shown to improve cell survival of both normal and cancer cells following DNA damage. Here, I will discuss the role of integrins and integrin-mediated signaling cascades in the survival or death response upon genotoxic stress. Detailed knowledge of the responsible molecular processes might provide implications for putative therapies targeting integrins or integrin-associated molecules to achieve an optimization of anticancer treatments.

Up-regulation of focal adhesion kinase in non-small cell lung cancer

Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase linked to the integrin and growth factor receptor-signalling pathways that regulates a number of the biological processes involved in neoplastic transformation, invasion and metastases, such as cell adhesion, migration and apoptosis. Its up-regulation might play a role in the tumourigenesis of invasive tumours, but its involvement in human lung cancer tissues has not yet been determined. We immunohistochemically compared FAK expression and localisation in 60 formalin-fixed and paraffin-embedded non-small cell lung cancer (NSCLC) tissues with that in the surrounding non-neoplastic tissue and in a further five microscopically normal lungs. FAK mRNA levels were quantitatively determined by real-time RT-PCR in frozen tissue specimens of all of the tumours and 21 matched non-neoplastic lung parenchymas, and protein expression in 16 homogenates of the matched neoplastic/non-neoplastic specimens was evaluated by Western blotting. The three different techniques showed that FAK is weakly expressed in non-neoplastic lung parenchyma and up-regulated in NSCLCs. Moreover, Western blotting and real-time RT-PCR indicated a statistically significant correlation between FAK up-regulation and higher disease stages (I+II versus III+IV, p=0.019 and 0.028, respectively). Our results provide evidence that FAK is up-regulated in NSCLCs, and suggest its potential involvement in lung cancer progression.

beta1-integrin-mediated signaling essentially contributes to cell survival after radiation-induced genotoxic injury

Integrin-mediated adhesion to extracellular matrix proteins confers resistance to radiation- or drug-induced genotoxic injury. To analyse the underlying mechanisms specific for beta1-integrins, wild-type beta1A-integrin-expressing GD25beta1A cells were compared to GD25beta1B cells, which express signaling-incompetent beta1B variants. Cells grown on fibronectin, collagen-III, beta1-integrin-IgG or poly-l-lysine were exposed to 0-6 Gy X-rays in presence or depletion of growth factors and phosphatidylinositol-3 kinase (PI3K) inhibitors (LY294002, wortmannin). In order to test the relevance of these findings in tumor cells, human A-172 glioma cells were examined under the same conditions after siRNA-mediated silencing of beta1-integrins. We found that beta1A-integrin-mediated adhesion to fibronectin, collagen-III or beta1-IgG was essential for cell survival after radiation-induced genotoxic injury. Mediated by PI3K, pro-survival beta1A-integrin/Akt signaling was critically involved in this process. Additionally, the beta1-integrin downstream targets p130Cas and paxillin-impaired survival-regulating PI3K-dependent JNK. In A-172 glioma cells, beta1-integrin knockdown and PI3K inhibition confirmed the central role of beta1-integrins in Akt- and p130Cas/paxillin-mediated prosurvival signaling. These findings suggest beta1-integrins as critical regulators of cell survival after radiation-induced genotoxic injury. Elucidation of the molecular circuitry of prosurvival beta1-integrin-mediated signaling in tumor cells may promote the development of innovative molecular-targeted therapeutic antitumor strategies.

Increased expression of ICAM-3 is associated with radiation resistance in cervical cancer

To search for a marker that predicts the efficacy of radiation therapy in human cervical cancer, gene expression profiles between parental SiHa cervical cancer cells and radiation-resistant SiHa/R cells have been compared by the microarray technique. Microarray and Northern blot analyses demonstrated that the ICAM-3 expression was upregulated in SiHa/R cells. This increased expression of ICAM-3 in SiHa cells enhanced cell survival by about 34.3% after a 2 Gy dosage of radiation. In addition, SiHa/ICAM-3 cells showed a 2.45-fold higher level of FAK phosphorylation than that of the control cells. In tumor specimens, ICAM-3 staining was restricted to tumor stromal endothelial cells and lymphocytes. The overexpression of ICAM-3 was significantly more frequent in radiation-resistant cervical cancer specimens when compared with radiation-sensitive specimens (83.3% vs. 35.3%; p = 0.015). With these observations, we can suggest that an increased expression of ICAM-3 is associated with radiation resistance in cervical cancer cells and the expression of ICAM-3 can be used as a valuable biomarker to predict the radiation resistance in cervical cancer that occurs during radiotherapy.