Temozolomide inhibits the migration of immune cells into the brain tumor microenvironment and their systemic expansion, but exerts a synergistic anti-tumor effect when combined with combined conditional cytotoxic/immune-gene therapy

MARIA G CASTRO; MARIANELA CANDOLFI; KADER YAGIZ; KURT M KROEGER; DAVID FOULAD; GABRIELLE E ALZADEH; MATTHEW TESARFREUND; PEDRO R LOWENSTEIN

Washington DC, EEUU

Congreso; American Society of Cell and Gene Therapy 13 Annual Meeting; 2010

Glioblastoma multiforme (GBM), the most common primary brain cancer in adults, carries a dismal prognosis, in spite of the most advanced standard of care. Treatment with temozolomide (TMZ) in addition to surgery and radiotherapy has increased median survival of GBM patients from 8 to 20 months. Nevertheless, the three year survival is still 5%. Thus, novel experimental approaches could be useful adjuvants for the treatment for GBM. Our previous results show that inta-tumoral administration of an adenoviral vector expressing Flt3L recruits antigen presenting cells to intracranial GBM. However, this is not enough to induce anti-tumor immunity; tumor cell death is required to release tumor antigen and intracellular inflammatory molecules which act as Toll receptor agonists. Considering that TMZ constitutes the standard of care for GBM patients, in the present work we aimed to combine intra-tumoral administration of Ad-Flt3L/Ad- TK with systemic TMZ in order to assess its impact on therapeutic efficacy in syngenic intracranial GBM models. Although treatment with TMZ alone led to a discreet improvement in survival ( 40% increase in median survival compared to saline controls), combined TMZ + Ad-Flt3L immune-gene therapy significantly increased the survival of mice bearing intracranial gliomas or metastatic melanoma. GL26 and GL261 tumor-bearing mice exhibited 40% and 20% long term survival, respectively, upon treatment with TMZ+Ad-Flt3L. While B16-F10 intracranial melanoma-bearing mice treated with saline had a median survival of 27 d, TMZ+Ad-Flt3L-treated mice exhibited a median survival of 48 d. The anti-tumor effect was further enhanced when intratumoral administration of conditionally cytotoxic Ad-TK+GCV was added to the chemo-immune gene therapeutic approach, leading to 50-70% long term survival in all three tumor models. The efficacy of this treatment was dependent on the release of the pro-inflammatory nuclear protein HMGB1 from dying tumor cells, induced by TMZ and Ad-TK treatment. In addition, the anti-tumor effect of this combined approach required an intact immune system, since the treatment failed when administered to mutant mice that lacked lymphocytes (CD4+, CD8+ T cells, and B cells) or dendritic cells. Our results contradict the traditional dogma that chemotherapy invariably leads to a state of immune-suppression that impairs the ability of the immune system to mount an effective anti-tumor response. Here we show that combination of chemotherapy and other cytotoxic agents with immunotherapy leads to synergistic antitumor efficacy and supports its clinical implementation in patients with GBM.