Activation of p53 by Nutlin-3a Induces Apoptosis and Cellular Senescence in Human Glioblastoma Multiforme

Abstract

Glioblastoma multiforme (GBM) is the most common and aggressive primary brain tumor in adults. Despite concerted efforts to improve current therapies and develop novel clinical approaches, patient survival remains poor. As such, increasing attention has focused on developing new therapeutic strategies that specifically target the apoptotic pathway in order to improve treatment responses. Recently, nutlins, small-molecule antagonists of MDM2, have been developed to inhibit p53-MDM2 interaction and activate p53 signaling in cancer cells. Glioma cell lines and primary cultured glioblastoma cells were treated with nutlin-3a. Nutlin-3a induced p53-dependent G1- and G2-M cell cycle arrest and apoptosis in glioma cell lines with normal TP53 status. In addition, nutlin-arrested glioma cells show morphological features of senescence and persistent induction of p21 protein. Furthermore, senescence induced by nutlin-3a might be depending on mTOR pathway activity. In wild-type TP53 primary cultured cells, exposure to nutlin-3a resulted in variable degrees of apoptosis as well as cellular features of senescence. Nutlin-3a-induced apoptosis and senescence were firmly dependent on the presence of functional p53, as revealed by the fact that glioblastoma cells with knockdown p53 with specific siRNA, or cells with mutated or functionally impaired p53 pathway, were completely insensitive to the drug. Finally, we also found that nutlin-3a increased response of glioma cells to radiation therapy. The results provide a basis for the rational use of MDM2 antagonists as a novel treatment option for glioblastoma patients.

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

“…Nutlin-3a was the lead compound in the field 57 but few data addressed its effects in GBM. Here, we show that it activated p53-dependent transcription of pro-apoptotic targets but also repressed anti-apoptotic genes confirming other works 25 without inducing full apoptosis in glioma cells overexpressing the α5β1 integrin. Repression of anti-apoptotic/survival genes in addition with induction of pro-apoptotic targets was shown to critically control the apoptotic outcome of RITA-treated cancer cells.…”

“…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.…”

Mdm2 antagonists induce apoptosis and synergize with cisplatin overcoming chemoresistance in TP53 wild‐type ovarian cancer cells

“…The results suggested that upon single Nut3a and double Nut3a-CDDP treatment, cells overexpressing Survivin showed decreased apoptosis compared to cells expressing basal levels of Survivin, although the differences were not statistically significant, which is in accordance with the previously published data. 13,29 Thus, overexpression of Survivin would be unable by itself to abolish apoptosis completely in OVCa cells. Nevertheless, downregulation of Survivin still may play a role in apoptosis induction in concert with other changes induced by Nut3a.…”

“…The induction of senescence by Nut3a has already been described by our group in the human glioblastoma multiforme model. 13 The double treatment caused cell lines enter into cell-cycle arrest in G2/M phase, and, in primary cell cultures, the persistent induction of p21 protein observed suggested that cellcycle arrest exceeded the duration of treatment. Arrested cells would go senescent (majority of primary cell cultures) or apoptotic (primary cell cultures and mainly cell lines), thus decreasing the growth of tumor cells.…”

“…In preclinical studies, Nut3a displayed increased potential for the treatment of human cancer cells harboring wild-type TP53 in [6][7][8][9] which the downstream p53-dependent signaling is preserved. Nut3a appears cytostatic to proliferating normal cells and induces p53-dependent apoptosis in human cancer cells such as osteosarcoma 9 and colon cancer, 8 acute myelogenous leukemia, 10 lung cancer, 11 chronic lymphocytic leukemia, 12 glioblastoma 13 and head and neck squamous cell carcinoma. 14 Chemotherapy based on CDDP has been hindered by its nephrotoxicity, neurotoxicity and myelotoxicity, 15 and so lower doses of the drug are needed to palliate the secondary effects.…”