Conjugation with nanodiamonds via hydrazone bond fundamentally alters intracellular distribution and activity of doxorubicin.

Doxorubicin (DOX) has been widely incorporated in various delivery forms for tareted treatment of malignant tumors such as triple-negative breast cancer (TNBC), with numerous studies reporting higher therapeutic efficacy and lower toxicity at the same time. However, little attention has been paid to whether DOX in a delivery form acts with the same actions and processes as in free form at the cellular level. This question was investigated in the present study wherein DOX conjugated with polyglycerol-coated nanodiamonds through the pH-sensitive hydrazone bond (Nano-DOX) was compared with DOX in free form on the 4T1 mouse TNBC model. We first found Nano-DOX to have a distinct intracellular distribution profile from DOX. Internalized Nano-DOX mainly stayed in the lysosomes slowly releasing DOX into the cytoplasm and then the nucleus whereas DOX displayed both nuclear and lysosomal distribution after cell uptake. Next, Nano-DOX was shown to induce endoplasmic reticulum (ER) stress without substantial DNA damage while DOX caused massive DNA damage as well as ER stress. Consequently, Nano-DOX only caused minimal activation of pro-inflammatory signaling mediated by MAPK/ERK, NF-κB and STAT3 as seen in response to DOX-inflicted DNA damage. Consistently, DOX-induced activities of ABC transporters, CXCL-1, GM-CSF and IL-6, which are tumor protective events downstream to the pro-inflammatory signaling, were also minimal in Nano-DOX-treated cancer cells. These findings are compelling proof that a chemotherapy in nano form can have distinct intracellular pharmacokinetics from its free from, which can result in altered cellular effects of the drug. Implications of these findings are discussed with an emphasis on nano-drug design, tumor pharmacology and chemoresistance.

Doxorubicin-polyglycerol-nanodiamond conjugates disrupt STAT3/IL-6-mediated reciprocal activation loop between glioblastoma cells and astrocytes.

Astrocytes are key stromal components in glioblastoma (GBM) and have complex interactions with the GBM cells (GBC) promoting the survival, progression and therapy resistance of GBM. In this study, we first demonstrated the existence of a reciprocal activation loop mediated by the STAT3/IL-6 signaling between GBC and astrocytes. This loop of reciprocity was found to be initiated by the constitutive activity of STAT3 and downstream expression of IL-6 in the GBC. GBC-derived IL-6 activated STAT3 and thereby upregulated IL-6 expression in the astrocytes. Astrocyte-derived IL-6 acted back on the GBC causing further activation of STAT3 and leading to enhanced downstream events that promote proliferation, migration, invasion and apoptosis resistance of the GBC. Next, we showed that doxorubicin-polyglycerol-nanodiamond conjugates (Nano-DOX), which could be delivered via GBM-associated macrophages, suppressed STAT3 activity in the GBC reducing their IL-6 output to the astrocytes and thereby abolished the astrocytes' feedback activation of the GBC. Moreover, Nano-DOX also suppressed stimulated activation of STAT3 and IL-6 induced by temozolomide, a first-line anti-GBM chemotherapy, resistance to which critically involves STAT3 activation. In conclusion, Nano-DOX could disrupt the STAT3/IL-6-mediated reciprocal activation loop between the GBC and astrocytes. Nano-DOX also provides a novel approach to therapeutic modulation of the GBM microenvironment.

Doxorubicin-polyglycerol-nanodiamond conjugate is a cytostatic agent that evades chemoresistance and reverses cancer-induced immunosuppression in triple-negative breast cancer.

BACKGROUND: Triple negative breast cancer (TNBC) has the poorest prognosis of all breast cancer subtypes and is one of the most fatal diseases for women. Combining cytotoxic chemotherapy with immunotherapy has shown great promise for TNBC treatment. However, chemotherapy often leads to the development of chemoresistance and severe systemic toxicity compromising the immune functions that are crucial to anti-TNBC immune therapy. Tumor-induced immunosuppression also poses a great hindrance to efficacious anti-TNBC immunotherapy. Nanomedicine holds great promise to overcome these hurdles. RESULTS: Doxorubicin-polyglycerol-nanodiamond conjugate (Nano-DOX) was firstly found to be a cytostatic agent to the 4T1 cells and displayed a lower apparent therapeutic potency than DOX. However, the tumor-bearing animals, particularly some key immune cells thereof, showed good tolerance of Nano-DOX as opposed to the severe toxicity of DOX. Next, Nano-DOX did not induce significant upregulation of P-gp and IL-6, which were demonstrated to be key mediators of chemoresistance to DOX in the 4T1 cells. Then, Nano-DOX was shown to downregulate tumor-derived granulocyte-colony stimulating factor (G-CSF) and suppresses the induction and tissue filtration of myeloid-derived suppressor cells (MDSCs) that are the principal effectors of cancer-associated systemic immunosuppression. Nano-DOX also alleviated the phenotype of MDSCs induced by 4T1 cells. Finally, Nano-DOX induced the 4T1 cells to emit damage associated molecular patterns (DAMPs) that stimulated the tumor immune microenvironment through activating key immune effector cells involved in anti-tumor immunity, such as macrophages, dendritic cells and lymphocytes in the tumor tissue. CONCLUSIONS: Nano-DOX is a cytostatic agent with good host tolerance which is capable of evading chemoresistance and reversing cancer-induced immunosuppression both at the systemic level and in the tumor microenvironment in TNBC. Our work presents Nano-DOX as an interesting example that a chemotherapeutic agent in nano-form may possess distinct biochemical properties from its free form, which can be exploited to join chemotherapy with immunotherapy for better treatment of cancer.

Doxorubicin-polyglycerol-nanodiamond composites stimulate glioblastoma cell immunogenicity through activation of autophagy.

Immunosuppression is a salient feature of GBM associated with the disease's grim prognosis and the limited success of anti-GBM immunotherapy. Stimulating immunogenicity of the GBM cells (GC) is a promising approach to subverting the GBM-associated immunosuppression. We had previously devised a drug composite based on polyglycerol-functionalized nanodiamonds bearing doxorubicin (Nano-DOX) and demonstrated that Nano-DOX effectively modulated GBM's immunosuppressive microenvironment through stimulating the immunogenicity of GC and initiated anti-GBM immune responses. The present study now explored the mechanism of Nano-DOX's immunostimulatory action. Nano-DOX was found to induce autophagy rather than apoptosis in GC and stimulated GC to emit antigens and damage-associated molecular patterns (DAMPs) that are potent adjuvants, which resulted in enhanced activation of dendritic cells (DC). Heightened autophagosome release was observed in Nano-DOX-treated GC but was shown not to be a major channel of antigen donation. Blocking autophagy in GC not only reduced Nano-DOX-stimulated GC antigen donation and DAMPs emission, but also efficiently attenuated DC activation stimulated by Nano-DOX-treated GC. Taken together, these findings suggest that activation of autophagy is a central mechanism whereby Nano-DOX stimulates GC's immunogenicity. Our work provides new insight on how nanotechnology can be applied to therapeutically modulate the GBM immune microenvironment by harnessing autophagy in the cancer cells. STATEMENT OF SIGNIFICANCE: Immunosuppression is a salient feature of GBM associated with the grim prognosis of the disease and the limited success of anti-GBM immunotherapy. We demonstrated that Doxorubicin-polyglycerol-nanodiamond composites could activate autophagy in GBM cells and thereby stimulate the immunogenecity of GBM cells. This discovery 1, sheds new light on how nanotechnology could be applied to therapeutically modulate the tumor immune microenvironment, and 2, provides a powerful tool for subverting the GBM's immunosuppressive microenvironment, which has great therapeutic potential for the treatment of GBM.

Dendritic cell-mediated delivery of doxorubicin-polyglycerol-nanodiamond composites elicits enhanced anti-cancer immune response in glioblastoma.

Glioblastoma (GBM) is the deadliest and most common type of primary brain tumor in adults with a grim prognosis despite multimodal treatments. Dendritic cell (DC)-based immunotherapy has emerged as a promising therapeutic modality for GBM, whose efficacy is nonetheless fundamentally undermined by GBM-induced immunosuppression. Inducing emission of damage associated molecular patterns (DAMPs) is a highly effective strategy to subvert tumor-associated immunosuppression. The present work was carried out to explore the idea of subverting the GBM immunosuppressive microenvironment through DC-mediated delivery of doxorubicin-polyglycerol-nanodiamond composites (Nano-DOX), a potent DAMPs inducer demonstrated by our previous study, and thereby eliciting enhanced DC-driven anti-GBM immune response. In the in-vitro work on human cell models, Nano-DOX-loaded DC were shown to be functionally viable and release cargo drug to co-cultured GBM cells (GC). Nano-DOX-treated GC displayed not only profuse DAMPs emission but also antigen release. Enhanced activation and acquisition and presentation of GC-derived antigen were then demonstrated in DC in co-culture with GC and Nano-DOX. Consistently, co-culture with GC and Nano-DOX also activated mouse bone marrow-derived DC (mDC) which in turn stimulated mouse spleen-derived lymphocytes which ultimately suppressed co-cultured GC. Next, athymic mice bearing orthotopic human GBM xenografts were intravenously injected with Nano-DOX-loaded mDC and, 48 h later, spleen-derived lymphocytes. The presence of Nano-DOX, DAMPs emission and enhanced infiltration and activation of mDC and lymphocytes were detected in the GBM xenografts. Taken together, our results demonstrate the efficacy of DC-mediated delivery of Nano-DOX to stimulate GC immunogenicity and elicit anti-cancer immune response in the GBM. By this work, we present a novel approach with great application potential to subverting the GBM immunosuppressive microenvironment and to anti-GBM immunotherapy. Investigation has also been conducted probing the mechanisms by which Nano-DOX stimulates GC immunogenicity, which is described in a follow-up paper.

Effect of toad skin extracts on the pain behavior of cancer model mice and its peripheral mechanism of action.

The changes in thermal and mechanical hyperalgesia in paw cancer pain model mice and the action mechanism of toad skin extracts (TSE) was investigated. Eighty female mice were subcutaneously injected with saline or inoculated with H22 hepatoma cells in the right hind paw and administration with saline, vehicle, morphine and TSE. The pain behavior was recorded before treatment and at 0.5, 1.0, 1.5, 3 and 6h after initial administration, and thereafter on the 2nd, 4th, 6th, and 8th day after administration. On the last day, samples were collected after the euthanasia for the detection of ß-END, CRF, IL-1ß, POMC, µ-OR, CD3+, CD8+ and CD4+ in sera and the tumor tissues. The results showed that TSE significantly increased the thresholds of thermal pain and mechanical pain, and upregulated the expressions of ß-END, CRF, POMC, CD3+, CD8+ and µ-OR, and downregulated the expression of CD4+. These results indicate that TSE significantly relieved pain in cancer pain model mice and raised their pain threshold. In addition, TSE seems to play a prominent role in promoting the activity of tumor infiltrating lymphocytes (TILs, CD3+ and CD8+ T cells), and this immune-cell-derived peripheral analgesic pathway might have widespread potential for clinical use.

Mechanism of QHF-cisplatin against hepatocellular carcinoma in a mouse model.

AIM: To study the effects of QHF-cisplatin on H22 hepatocellular carcinoma (HCC) and their mechanisms of action. METHODS: Sixty BALB/c mice were randomly divided into a model group (n = 48) and a normal control group (n = 12). An HCC xenograft tumor was created by injecting H22 cells directly into the liver parenchyma of the mice. The 48 BALB/c mice in the model group were randomly divided into four groups: QHF, DDP (cisplatin), QHF plus DDP, and model control. The inhibitory effects of these drugs on tumor growth were evaluated by calculating the rate of tumor growth inhibition. The mice were examined by observing their general condition, body weight and survival time. Changes in tumor tissue were observed under an optical microscope. Aspartate aminotransferase (AST), alanine aminotransferase (ALT) and α-fetoprotein (AFP) levels in serum were measured. Hepatocyte growth factor (HGF), c-mesenchymal-epithelial transition (c-Met) factor, phosphorylated (p)-c-Met, p38, p-p38, extracellular signal-regulated kinase (ERK), p-ERK and vascular endothelial growth factor (VEGF) levels were evaluated in tumor and liver tissues using western blotting. RESULTS: Compared with the DDP group, a lower incidence of toxic reactions and a higher survival time were observed in the QHF plus DDP group. Tumor weight was significantly lower in the QHF, DDP and QHF plus DDP groups than in the model control group (0.24 ± 0.07, 0.18 ± 0.03 and 0.14 ± 0.01 g vs 0.38 ± 0.05 g, respectively), and the differences were statistically significant (P < 0.01). The rate of tumor growth inhibition in the QHF, DDP and QHF plus DDP groups was 38.7%, 52.6% and 63.5%, respectively. AST, ALT and AFP levels in serum were significantly lower in the QHF, DDP and QHF plus DDP groups compared to the model control group (P < 0.05). Similarly, HGF, p-c-Met, p-p38, p-ERK and VEGF levels in tumor tissue were significantly lower in the QHF, DDP and QHF plus DDP groups (P < 0.05). CONCLUSION: QHF and DDP have an antiangiogenic effect on H22 HCC in mice. QHF inhibits tumor growth via blocking the HGF/c-Met signaling pathway, inhibiting p38, ERK and VEGF signaling.