Serum integrin-linked kinase (sILK) concentration and survival in non-small cell lung cancer: a pilot study

Integrin-linked kinase (ILK): the known vs. the unknown and perspectives

Integrin-linked kinase (ILK) is a multifunctional molecular actor in cell-matrix interactions, cell adhesion, and anchorage-dependent cell growth. It combines functions of a signal transductor and a scaffold protein through its interaction with integrins, then facilitating further protein recruitment within the ILK-PINCH-Parvin complex. ILK is involved in crucial cellular processes including proliferation, survival, differentiation, migration, invasion, and angiogenesis, which reflects on systemic changes in the kidney, heart, muscle, skin, and vascular system, also during the embryonal development. Dysfunction of ILK underlies the pathogenesis of various diseases, including the pro-oncogenic activity in tumorigenesis. ILK localizes mostly to the cell membrane and remains an important component of focal adhesion. We do know much about ILK but a lot still remains either uncovered or unclear. Although it was initially classified as a serine/threonine-protein kinase, its catalytical activity is now questioned due to structural and functional issues, leaving the exact molecular mechanism of signal transduction by ILK unsolved. While it is known that the three isoforms of ILK vary in length, the presence of crucial domains, and modification sites, most of the research tends to focus on the main isoform of this protein while the issue of functional differences of ILK2 and ILK3 still awaits clarification. The activity of ILK is regulated on the transcriptional, protein, and post-transcriptional levels. The crucial role of phosphorylation and ubiquitylation has been investigated, but the functions of the vast majority of modifications are still unknown. In the light of all those open issues, here we present an extensive literature survey covering a wide spectrum of latest findings as well as a past-to-present view on controversies regarding ILK, finishing with pointing out some open questions to be resolved by further research.

Mechanism of intrinsic resistance of lung squamous cell carcinoma to epithelial growth factor receptor-tyrosine kinase inhibitors revealed by high-throughput RNA interference screening

Although targeted therapy has achieved a great breakthrough in the treatment of lung adenocarcinoma, there are still no effective targeted drugs for lung squamous cell carcinoma (SqCC). In addition, as immunotherapy can only prolong the overall survival (OS) of lung SqCC by ≤5 months, chemotherapy and radiotherapy are still the main types of therapy for advanced SqCC. The expression level of epithelial growth factor receptor (EGFR) in patients with lung SqCC is higher compared with those with adenocarcinoma, but the former group is intrinsically resistant to EGFR-tyrosine kinase inhibitors (EGFR-TKIs). Therefore, if the drug resistance in patients with lung SqCC could be reversed, the majority of patients may benefit from EGFR-TKIs. In the present study, the high-throughput RNA interference technology was used to screen the genes involved in the EGFR-TKI erlotinib resistance of lung SqCCs, and integrin-linked kinase (ILK) was identified to be the most effective. The role of ILK in erlotinib resistance was further studied in cell lines, and the expression of ILK was analyzed in patients with SqCC and adenocarcinoma. Finally, the mechanism of ILK in EGFR-TKIs resistance was analyzed using Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene Ontology (GO) and ingenuity pathway analysis (IPA). The results demonstrated that the ILK gene knockdown could overcome erlotinib resistance by inhibiting cell proliferation, inducing apoptosis and blocking the cell cycle at the G2/M phase. The expression of ILK in patients with SqCC was significantly higher compared with those with adenocarcinoma with sensitizing EGFR mutations. In addition, the cell cycle pathway 'G2/M DNA damage and checkpoint regulation' was identified to be significantly inhibited by ILK knockdown in IPA, KEGG and GO analysis. The results of the present study may improve the understanding of EGFR-TKI resistance in lung SqCCs, thus promoting the development of potential targeted therapies for lung SqCCs.

RNA silencing of integrin-linked kinase increases the sensitivity of the A549 lung cancer cell line to cisplatin and promotes its apoptosis

The expression of integrin-linked kinase (ILK) has been reported to be involved in the regulation of integrin-mediated processes, including cancer cell proliferation, migration and invasion. Previous studies have demonstrated that inhibition of ILK may be an underlying approach for treating cancer. However, whether the knock down of ILK affects growth and apoptosis of lung cancer cells remains to be elucidated. Importantly, whether downregulation of ILK increases the sensitivity of lung cancer cells to cisplatin and amplifies cell apoptosis also remains to be elucidated. In the present study, ILK downregulation was mediated by lentivirus-mediated RNA interference. The expression levels of associated genes were determined by reverse-transcription quantitative polymerase chain reaction and western blotting. Cell proliferation was evaluated using a modified 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and clone formation assay. The cell cycle and apoptosis were analyzed using flow cytometry. The current data revealed that lentivirus-mediated ILK gene silencing alone inhibited A549 cell proliferation and promotes cell cycle arrest, however, had no detectable effect on cell apoptosis. However, combined treatment with lentivirus-mediated ILK interference and cisplatin chemotherapy induced significantly more cell apoptosis than mono-chemotherapy or knockdown. The increased cell apoptosis and proliferation inhibition were attributed to abnormal downstream protein expression of ILK, including phospho-glycogen synthase kinase 3β, p-AKT, activator protein-1, β-catenin, cyclin D1 and matrix metalloproteinase-9. ILK inhibition may suppress the proliferation of A549 and increase A549 sensitivity to cisplatin. The combined treatment of ILK gene knockdown and chemotherapy has the potential to improve anticancer efficacy.