α5β1 integrin antagonists reduce chemotherapy‐induced premature senescence and facilitate apoptosis in human glioblastoma cells

Abstract

The a5b1 integrin represent a new therapeutic target for glioblastoma, which are malignant brain tumors difficult to cure with conventional therapies. Glioblastoma are known to be highly resistant to chemotherapy. We, therefore, investigated whether blocking a5b1 integrin with specific nonpeptidic antagonists concomitantly with chemotherapy (ellipticine and temozolomide) may impact the response to chemotherapy of human glioblastoma. Here we show that inhibiting a5b1 integrin with 2 selective ligands (SJ749 and K34c) decreases chemotherapy-induced premature senescence and facilitates cell apoptosis in a functional p53 background (U87MG cells). When p53 is mutated and inactive (U373 cells), chemotherapy induces p53-independent cell apoptosis instead of senescence that is not improved by integrin antagonists. Silencing p53 in U87MG cells with siRNA as well as evaluating HCT116 p531/1 and p532/2 colon carcinoma cell behavior support the hypothesis of an as yet unknown effect of a5b1 integrin antagonists on the control of chemotherapy-induced premature senescence and apoptosis. a5b1 integrin antagonists modulate the p53 signaling induced by chemotherapy. Our results highlight a new role of the a5b1 integrin in the control of glioblastoma aggressiveness and responsiveness to chemotherapy, which may have a crucial impact in the clinical management of patients suffering from brain tumors.The median survival of patients diagnosed with grade IV astrocytomas (glioblastoma multiforme or GBM) is less than a year whatever the conventional therapies chosen (surgery, radiotherapy and/or chemotherapy). Therefore, new alternatives are highly needed. Integrins were recently identified as potential therapeutic targets as they take part in various cancer stages such as malignant transformation, tumor growth and progression, invasion and metastasis and angiogenesis. Particular emphasis has been given to avb3/b5 integrins that are overexpressed in neovessels nourishing the tumor. A avb3/b5 antagonist, cilengitide, is currently undergoing clinical trials to target neoangiogenesis in malignant glioma. 1,2 The a5b1 integrin emerged more recently as a potential anti cancer target as it is overexpressed in both tumoral neovessels 3,4 and tumoral cells and appears now as an interesting therapeutic target for brain, 5-7 lung 8 and ovarian tumors. 9 The expression of the a5b1 integrin is related to the tumor stage of gliomas 5 and the integrin signaling pathways were identified as being part of functional networks of GBM. 10 Because of the recent interest in a5b1 integrin, design of specific non peptidic ligands has increased these last years. [11][12][13] Nonpeptidic small a5b1 integrin antagonists were already shown to block angiogenesis and lymphangiogenesis. 14-16 Focusing on brain tumors, we have recently shown that perturbing specifically the function of the a5b1 integrin with the prototypical antagonist SJ749 in U87MG glioma cells triggers cell cycle arrest 6 and decreases cell aggressiveness. 7 In addition, we demonstrated that the ex...

Integrin α5β1 and p53 convergent pathways in the control of anti-apoptotic proteins PEA-15 and survivin in high-grade glioma

“…Along with others, we demonstrated that p53-induced activation either by genotoxic drugs 24 or by inhibitors of HDM2 such as Nutlin-3a-triggered 25 senescence rather than apoptosis in GBM. We characterized a negative crosstalk between α5β1 integrin and p53wt implicated in temozolomide (TMZ) resistance.…”

“…We demonstrated that α5β1 integrin interferes with the p53 pathway and that Nutlin-3a (10 μM) represses the α5 integrin subunit through the activation of p53. 8,24 We wondered whether α5 integrin repression would sensitize glioma cells to Nutlin-3a. We treated U87MG cells overexpressing (U87MG-α5 high) or repressed (U87MG-α5 low) for α5 integrin with different doses of Nutlin-3a and evaluated their clonogenic potential.…”

“…8 Antagonists of α5β1 integrin pushed TMZ-treated cells from senescence toward apoptosis while modulating the p53 pathway. 24 Nutlin-3a, by inhibiting p53-HDM2 interaction, induced a huge increase in p53 activity but also decreased the expression level of α5 integrin in p53wt GBM or colon cancer cells. 8,26 Here, we investigated the potential benefit of targeting GBM with antagonists of α5β1 integrin and Nutlin-3a.…”

Integrin α5β1 Plays a Critical Role in Resistance to Temozolomide by Interfering with the p53 Pathway in High-Grade Glioma

“…Through the use of non-peptidic a5b1 integrin antagonists and GBM cell lines, we previously showed that a5b1 integrin may be a therapeutic target for these tumors (8,9) and that concomitant addition of a5b1 antagonists sensitizes p53 wild-type (p53-wt) glioma cells to chemotherapeutic drugs (10). The presence of p53 mutations in high-grade glioma varied across GBM subtypes with 0%, 21%, 32%, and 54% in classical, neural, mesenchymal, and proneural subtypes, respectively (11).…”

Alternative responses of primary tumor cells and glioblastoma cell lines to N,N-bis-(8-hydroxyquinoline-5-yl methyl)-benzyl substituted amines: Cell death versus P53-independent senescence

“…Several senescence-inducing pathways have been described, the principal being the P19Arf/P53 axis. As P53 has been involved in Temozolomide induction of senescence in U87 cells (28) and because our gene expression analysis showed over-expression of P53 and P53 targets (2), we addressed the involvement of P53 in the response of U87 cells to HQNBA derivatives. First, we found that over-expression of P53 and a set of several potential P53 targets specifically occurred exclusively in the presence of bio-active HQNBA derivatives but not when HQNBA analogs belonging to the same chemical series but lacking activity on cell proliferation and migration were used.…”