Glioblastoma (GBM) is one of the most pernicious forms of cancer and currently chances of survival from this malady are extremely low. We have used the noninvasive strategy of intranasal (IN) delivery of a glioblastoma-directed adduct of curcumin (CC), CC-CD68Ab, into the brain of mouse GBM GL261-implanted mice to study the effect of CC on tumor remission and on the phenotype of the tumor-associated microglial cells (TAMs). The treatment caused tumor remission in 50% of GL261-implanted GBM mice. A similar rescue rate was also achieved through intraperitoneal infusion of a lipid-encapsulated formulation of CC, Curcumin Phytosome, into the GL261-implanted GBM mice. Most strikingly, both forms of CC elicited a dramatic change in the tumor-associated Iba1+ TAMs, suppressing the tumor-promoting Arginase1 , iNOS M2-type TAM population while inducing the Arginase1 , iNOS M1-type tumoricidal microglia. Concomitantly, we observed a marked induction and activation of microglial NF-kB and STAT1, which are known to function in coordination to cause induction of iNOS. Therefore, our novel findings indicate that appropriately delivered CC can directly kill GBM cells and also repolarize the TAMs to the tumoricidal M1 state.

Our earlier studies reported a unique potentiated combination (TriCurin) of curcumin (C) with two other polyphenols. The TriCurin-associated C displays an IC50 in the low micromolar range for cultured HPV+ TC-1 cells. In contrast, because of rapid degradation in vivo, the TriCurin-associated C reaches only low nano-molar concentrations in the plasma, which are sub-lethal to tumor cells. Yet, injected TriCurin causes a dramatic suppression of tumors in TC-1 cell-implanted mice (TC-1 mice) and xenografts of Head and Neck Squamous Cell Carcinoma (HNSCC) cells in nude/nude mice. Here, we use the TC-1 mice to test our hypothesis that a major part of the anti-tumor activity of TriCurin is evoked by innate and adaptive immune responses. TriCurin injection repolarized arginase1 (ARG1), IL10, inducible nitric oxide synthase (iNOS), IL12 M2-type tumor-associated macrophages (TAM) into ARG1, IL10, iNOS, and IL12 M1-type TAM in HPV+ tumors. The M1 TAM displayed sharply suppressed STAT3 and induced STAT1 and NF-kB(p65). STAT1 and NF-kB(p65) function synergistically to induce iNOS and IL12 transcription. Neutralizing IL12 signaling with an IL12 antibody abrogated TriCurin-induced intra-tumor entry of activated natural killer (NK) cells and Cytotoxic T lymphocytes (CTL), thereby confirming that IL12 triggers recruitment of NK cells and CTL. These activated NK cells and CTL join the M1 TAM to elicit apoptosis of the E6+ tumor cells. Corroboratively, neutralizing IL12 signaling partially reversed this TriCurin-mediated apoptosis. Thus, injected TriCurin elicits an M2→M1 switch in TAM, accompanied by IL12-dependent intra-tumor recruitment of NK cells and CTL and elimination of cancer cells.

BackgroundGlioblastoma (GBM) is a primary brain tumor with a 5-year survival rate of ≤5%. We have shown earlier that GBM-antibody-linked curcumin (CC) and also phytosomal curcumin (CCP) rescue 50–60% of GBM-bearing mice while repolarizing the tumor-associated microglia/macrophages (TAM) from the tumor-promoting M2-type to the tumoricidal M1-type. However, systemic application of CCP yields only sub-IC50 concentrations of CC in the plasma, which is unlikely to kill GBM cells directly. This study investigates the role of CC-evoked intra-GBM recruitment of activated natural killer (NK) cells in the elimination of GBM and GBM stem cells.MethodsWe have used an immune-competent syngeneic C57BL6 mouse model with the mouse-GBM GL261 cells orthotopically implanted in the brain. Using immunohistochemistry and flow cytometry, we have quantitatively analyzed the role of the intra-GBM-recruited NK cells by (i) injecting (i.p.) the NK1.1 antibody (NK1.1Ab) to temporarily eliminate the NK cells and (ii) blocking NK recruitment by injecting an IL12 antibody (IL12Ab). The treatment cohorts used randomly-chosen GL261-implanted mice and data sets were compared using two-tailed t-test or ANOVA.ResultsCCP treatment caused the GBM tumor to acquire M1-type macrophages (50–60% of the TAM) and activated NK cells. The treatment also elicited (a) suppression of the M2-linked tumor-promoting proteins STAT3, ARG1, and IL10, (b) induction of the M1-linked anti-tumor proteins STAT1 and inducible nitric oxide synthase in the TAM, (c) elimination of CD133(+) GBM stem cells, and (d) activation of caspase3 in the GBM cells. Eliminating intra-GBM NK cell recruitment caused a partial reversal of each of these effects. Concomitantly, we observed a CCP-evoked dramatic induction of the chemokine monocyte chemotactic protein-1 (MCP-1) in the TAM.ConclusionsThe recruited NK cells mediate a major part of the CCP-evoked elimination of GBM and GBM stem cells and stabilization of the TAM in the M1-like state. MCP-1 is known to activate peripheral M1-type macrophages to secrete IL12, an activator of NK cells. Based on such observations, we postulate that by binding to peripheral M1-type macrophages and IL12-activated NK cells, the brain-released chemokine MCP-1 causes recruitment of peripheral immune cells into the GBM, thereby causing destruction of the GBM cells and GBM stem cells.Electronic supplementary materialThe online version of this article (10.1186/s13046-018-0792-5) contains supplementary material, which is available to authorized users.

No abstract

Glioblastoma (GBM) is the most insidious form of primary adult brain tumor with a mean life expectancy of 12-24 months. Previously, we have used the non-invasive strategies of (1) intranasal delivery of a glioblastoma-directed curcumin (CC) adduct (CC-CD68Ab) and (2) the intraperitoneal (i.p.) infusion of a lipid-encapsulated formulation of CC-phytosome to rescue orthotopically GL261-implanted GBM mice and study the effect of CC on the phenotype of the tumor-associated microglial cells (TAMs). Both treatment regimens not only caused tumor remission in 50-60% of GL261-implanted GBM mice, but also induced a dramatic change in the tumor-associated Iba1+ TAMs, suppressing the tumor-promoting Arginase1high, IL10high, iNOSlow, IL12low M2-type TAMs, while simultaneously inducing the Arginase1low, IL10low, iNOShigh, IL12high M1-type TAMs. Concurrently, we observed a marked induction and phosphorylation-mediated activation of microglial p65 NF-kB and STAT1, with concomitant suppression and inactivation of STAT3. p-STAT1high, p-STAT3low M1 microglia are known to cause IL12-dependent recruitment/activation of tumoricidal NKp46high natural killer (NK) cells. In determining the kinetics of CC-induced M1 repolarization of M2-TAMs, we observed that five days of CCP treatment (i.p.) was sufficient to induce a dramatic change in the tumor-associated Iba1+ TAMs, inhibiting the tumor-promoting M2-type TAM population, while activating M1-type microglia. As expected, we observed a concomitant recruitment of NKp46high NK cells into the GBM tumor. Cognizant of the fact that NK cells activate and stabilize the M1-microglia, we eliminated the NK cells in these GBM mice using the NK cell-targeted antibody NK1.1 Ab to observe a significant reduction in CC-evoked repolarization of TAMs. Our results demonstrate a unique oncoimmunotherapeutic function of CC, which when appropriately delivered, not only eliminates GBM directly, but also indirectly elicits recruitment and activation of tumoricidal NK cells and M1-TAMs. Furthermore, maintenance of this CC-evoked M1 phenotype is contingent upon CC-induced recruitment and activation of NK cells. Thus, when delivered appropriately, CC functions on GBM both directly as well as by stimulating and recruiting an army of immune cells that eliminate both GBM and GBM-initiating cells. Citation Format: Sumit Mukherjee, Angela Fried, Rahman Hussaini, Richard White, Aheli Chatterjee, Probal Banerjee. Appropriately delivered curcumin causes recruitment of natural killer cells into glioblastoma brain, stabilizing M1 polarization of tumor-associated microglia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4577. doi:10.1158/1538-7445.AM2017-4577