Inhibition of melanoma growth by subcutaneous administration of hTERTC27 viral cocktail in C57BL/6 mice

Targeting Telomere Dynamics as an Effective Approach for the Development of Cancer Therapeutics

Telomere is a protective structure located at the end of chromosomes of eukaryotes, involved in maintaining the integrity and stability of the genome. Telomeres play an essential role in cancer progression; accordingly, targeting telomere dynamics emerges as an effective approach for the development of cancer therapeutics. Targeting telomere dynamics may work through multifaceted molecular mechanisms; those include the activation of anti-telomerase immune responses, shortening of telomere lengths, induction of telomere dysfunction and constitution of telomerase-responsive drug release systems. In this review, we summarize a wide variety of telomere dynamics-targeted agents in preclinical studies and clinical trials, and reveal their promising therapeutic potential in cancer therapy. As shown, telomere dynamics-active agents are effective as anti-cancer chemotherapeutics and immunotherapeutics. Notably, these agents may display efficacy against cancer stem cells, reducing cancer stem levels. Furthermore, these agents can be integrated with the capability of tumor-specific drug delivery by the constitution of related nanoparticles, antibody drug conjugates and HSA-based drugs.

Targeted Photothermal Therapy of Melanoma in C57BL/6 Mice using Fe3O4@Au Core-shell Nanoparticles and Near-infrared Laser

BACKGROUND

Gold nanoshells can be tuned to absorb a particular wavelength of light. As a result, these tunable nanoparticles (NPs) can efficiently absorb light and convert it to heat. This phenomenon can be used for cancer treatment known as photothermal therapy. In this study, we synthesized Fe₃O₄@Au core-shell NPs, magnetically targeted them towards tumor, and used them for photothermal therapy of cancer.

OBJECTIVE

The main purpose of this research was to synthesize Fe₃O₄@Au core-shell NPs, magnetically target them towards tumor, and use them for photothermal therapy of cancer.

MATERIAL AND METHODS

In this experimental study, twenty mice received 2 × 10⁶ B16-F10 melanoma cells subcutaneously. After tumors volume reached 100 mm³, the mice were divided into five groups including a control group, NPs group, laser irradiation group, NPs + laser group and NPs + magnet + laser group. NPs were injected intravenously. After 6 hours, the tumor region was irradiated by laser (808 nm, 2.5 W/cm², 6 minutes). The tumor volumes were measured every other day.

RESULTS

The effective diameter of Fe₃O₄@Au NPs was approximately 37.8 nm. The average tumor volume in control group, NPs group, laser irradiation group, NPs + laser irradiation group and NPs + magnet + laser irradiation group increased to 47.3, 45.3, 32.8, 19.9 and 7.7 times, respectively in 2 weeks. No obvious change in the average body weight for different groups occurred.

CONCLUSION

Results demonstrated that magnetically targeted nano-photothermal therapy of cancer described in this paper holds great promise for the selective destruction of tumors.

Thiol antioxidants sensitize malabaricone C induced cancer cell death via reprogramming redox sensitive p53 and NF-κB proteins in vitro and in vivo

Specific focus on "redox cancer therapy" by targeting drugs to redox homeostasis of the cancer cells is growing rapidly. Recent clinical studies showed that N-acetyl cysteine (NAC) treatment significantly decreased the metabolic heterogeneity and reduced Ki67 (a proliferation marker) with simultaneous enhancement in apoptosis of tumor cells in patients. However, it is not yet precisely known how thiol antioxidants enhance killing of cancer cells in a context dependent manner. To this end, we showed that a dietary compound, malabaricone C (mal C) generated copious amounts of reactive oxygen species (ROS) and also reduced GSH level in lung cancer cells. Paradoxically, although antioxidants supplementation reduced mal C-induced ROS, thiol-antioxidants (NAC/GSH) restored intracellular GSH level but enhanced DNA DSBs and apoptotic cell death induced by mal C. Our results unraveled two tightly coupled biochemical mechanisms attributing this sensitization process by thiol antioxidants. Firstly, thiol antioxidants enable the "catechol-quinone redox cycle" of mal C and ameliorate ROS generation and bio-molecular damage (DNA and protein). Secondly, thiol antioxidants cause rapid glutathionylation of transcription factors [p53, p65 (NF-κB) etc.], oxidized by mal C, and abrogates their nuclear sequestration and transcription of the anti-apoptotic genes. Furthermore, analyses of the mitochondrial fractions of p53 expressing and silenced cells revealed that cytoplasmic accumulation of glutathionylated p53 (p53-SSG) triggers a robust mitochondrial death process. Interestingly, mutation of redox sensitive cysteine residues at 124, 141 and 182 position in p53 significantly reduces mal C plus NAC mediated sensitization of cancer cells. The preclinical results, in two different tumor models in mice, provides further support our conclusion that NAC is able to sensitize mal C induced suppression of tumor growth in vivo.

SEP enhanced the antitumor activity of 5-fluorouracil by up-regulating NKG2D/MICA and reversed immune suppression via inhibiting ROS and caspase-3 in mice

Chemotherapy and immunotherapy are the main remedies used in cancer treatment. Because immunotherapy can not only reduce the toxicity of chemotherapeutics but also enhance antitumor effects in vivo, combining these two therapies is a trend that continues to gain more attention in clinic. SEP, a polysaccharide isolated from Strongylocentrotus nudus egg, has been reported to display antitumor activity by stimulating immune cells, including NK and T cells, via TLR2 and TLR4. In the present study, the synergistic effect between SEP and 5-fluorouracil (5-FU), a traditional cytotoxic drug, in vitro and in vivo was investigated. The results obtained indicated that SEP alone stimulated NK-92 cytotoxicity and coordinated with 5-FU to augment the cytotoxicity of NK-92 cells against HepG-2 or A549 cells in vitro. SEP promoted NK-92 activity by stimulating NKG2D and its downstream DAP10/PI3K/Erk signaling pathway. Additionally, 5-FU could increase MICA expression on HepG-2 or A549 cells and prevent membrane MICA from shedding as soluble MICA, which were abrogated in the tumor cells transfected with ADAM 10 overexpression plasmid. Moreover, in H22- or Lewis lung cancer (LLC)-bearing mouse models, SEP reversed 5-FU-induced atrophy and apoptosis in both the spleen and bone marrow in vivo by suppressing ROS generation and caspase-3 activation. All of these results highlight the potential for the combination of SEP and 5-FU in cancer therapy in the future.

The anti-hepatocellular carcinoma activity of Mel-P15 is mediated by natural killer cells

Mel-P15 is a peptide derived from melittin, the main toxic component in the venom of the European honeybee Apis mellifera. In the present study, the antitumor effects of Mel-P15 and the underlying molecular mechanisms of these effects in vivo were investigated. Mel-P15 directly stimulated natural killer (NK) cell cytotoxicity in vitro, which was increased to 55.45% at a 4 µg/ml dose of Mel-P15. In the mouse liver cancer (H22) xenograft mice model, Mel-P15 suppressed tumor growth in vivo; the tumor inhibitory rate was 61.15% following treatment with 2 mg/kg Mel-P15. In addition, the immune response was activated following Mel-P15 treatment. Mel-P15 treatment increased the spleen and thymus indices, promoted splenocyte proliferation, stimulated NK cytotoxicity and upregulated the secretion of cytokines, including interleukin-2, interferon-γ and tumor necrosis factor-α. In addition, the tumor inhibitory effect of Mel-P15 on BEL-7402-bearing nude mice was abrogated by the selective depletion of NK cells via the intraperitoneal injection of an anti-asialo GM-1 antibody. The results suggest that Mel-P15 inhibits tumor growth in vivo by promoting NK cell cytotoxicity. Mel-P15 may therefore be a potential immunotherapy candidate for the treatment of hepatocellular carcinoma.

In Vitro and In Vivo Tumor Growth Inhibition by Glutathione Disulfide Liposomes

Glutathione disulfide (GSSG) is an endogenous peptide and the oxidized form of glutathione. The impacts of GSSG on cell function/dysfunction remain largely unexplored due to a lack of method to specifically increase intracellular GSSG. We recently developed GSSG liposomes that can specifically increase intracellular GSSG. The increase affected 3 of the 4 essential steps (cell detachment, migration, invasion, and adhesion) of cancer metastasis in vitro and, accordingly, produced a significant inhibition of cancer metastasis in vivo. In this investigation, the effect of GSSG liposomes on cancer growth was investigated with B16-F10 and NCI-H226 cells in vitro and with B16-F10 cells in C57BL/6 mice in vivo. Experiments were conducted to elucidate the effect on cell death through promotion of apoptosis and the effect on the cell cycle. The in vivo results with C57BL/6 mice implanted subcutaneously with B16-F10 cells showed that GSSG liposomes retarded tumor proliferation more effectively than that of dacarbazine, a chemotherapeutic drug for the treatment of melanoma. The GSSG liposomes by intravenous injection (GLS IV) and GSSG liposomes by intratumoral injection (GLS IT) showed a tumor proliferation retardation of 85% ± 5.7% and 90% ± 3.9%, respectively, compared with the phosphate-buffered saline (PBS) control group. The median survival rates for mice treated with PBS, blank liposomes, aqueous GSSG, dacarbazine, GLS IV, and GLS IT were 7, 7, 7.5, 7.75, 11.5, and 16.5 days, respectively. The effective antimetastatic and antigrowth activities warrant further investigation of the GSSG liposomes as a potentially effective therapeutic treatment for cancer.

Yessotoxin, a Marine Toxin, Exhibits Anti-Allergic and Anti-Tumoural Activities Inhibiting Melanoma Tumour Growth in a Preclinical Model

Yessotoxins (YTXs) are a group of marine toxins produced by the dinoflagellates Protoceratium reticulatum, Lingulodinium polyedrum and Gonyaulax spinifera. They may have medical interest due to their potential role as anti-allergic but also anti-cancer compounds. However, their biological activities remain poorly characterized. Here, we show that the small molecular compound YTX causes a slight but significant reduction of the ability of mast cells to degranulate. Strikingly, further examination revealed that YTX had a marked and selective cytotoxicity for the RBL-2H3 mast cell line inducing apoptosis, while primary bone marrow derived mast cells were highly resistant. In addition, YTX exhibited strong cytotoxicity against the human B-chronic lymphocytic leukaemia cell line MEC1 and the murine melanoma cell line B16F10. To analyse the potential role of YTX as an anti-cancer drug in vivo we used the well-established B16F10 melanoma preclinical mouse model. Our results demonstrate that a few local application of YTX around established tumours dramatically diminished tumour growth in the absence of any significant toxicity as determined by the absence of weight loss and haematological alterations. Our data support that YTX may have a minor role as an anti-allergic drug, but reveals an important potential for its use as an anti-cancer drug.

Antitumor effect of COOH-terminal polypeptide of human TERT is associated with the declined expression of hTERT and NF-κB p65 in HeLa cells

Human telomerase reverse transcriptase (hTERT) plays an important role in the development of tumors and has been investigated as a potent target for anticancer therapy. In the present study, we constructed a recombinant adenovirus, Ad-EGFP-C197 which was capable of expressing COOH‑terminal polypeptide of hTERT (amino acid 936-1,132, termed as C197 for the reason that it contains 197 amino acids). Infection of HeLa cells with Ad-EGFP-C197 suppressed the activity of telomerase, decreased the expression of hTERT and NF-κB p65, and induced rapid growth delay and apoptosis of HeLa cells in vitro. In nude mice xenografted with HeLa tumors, injection of Ad-EGFP-C197 into the tumor nodule significantly slowed tumor growth and promoted tumor cell apoptosis, as well as reduced the expression of NF-κB p65 in tumor tissues. In the present study, we suggest that the antitumor effect of C197 is associated with the declined expression of hTERT and NF-κB p65. Our results highlight the potential of C197 in tumor therapy.

Chronic intake of high fish oil diet induces myeloid-derived suppressor cells to promote tumor growth

Omega-3 polyunsaturated fatty acids enriched fish oil exerts beneficial anti-inflammatory effects in animal models with acute and chronic inflammatory diseases. Myeloid-derived suppressor cells (MDSCs), comprised of myeloid progenitors and precursors of myeloid cells, play vital roles in cancer. How fish oil affects the generation of MDSCs and the tumor development remains largely unexplored. Here, we show that dietary intake of high fish oil diet suppresses CD8(+) T cells activation and proliferation in vivo via elevated levels of MDSCs. Mechanistically, high fish oil diet induces the expression of immunosuppressive cytokine IL-10 and promotes myelopoiesis in the spleen as well as other peripheral tissues. The immature myeloid cells in the spleen exhibit morphological and functional characteristics of MDSCs with the capability to downregulate CD8(+) T cells activation. Depletion of MDSCs using anti-Gr-1 antibody decreases the growth of subcutaneously transferred B16 melanoma in mice on high fish oil diet. Interestingly, diet-induced production of MDSCs is not solely dependent of the spleen, as splenectomy has no effect on the tumor progress. Our data show that the liver functions as an alternative extramedullary hematopoiesis organ to support MDSCs differentiation and maintain tumor growth. Taken together, our study provides a novel insight into the physiological effects of fish oil and points to MDSCs as a possible mediator linking dietary fish oil intake and immunosuppression in cancer immunosurveillance.

The anti-lung cancer activity of SEP is mediated by the activation and cytotoxicity of NK cells via TLR2/4 in vivo

Strongylocentrotus nudus egg polysaccharide (SEP) has been reported to display antitumor activity. However, the effects of SEP and its underlying mechanism in the treatment of lung cancer remain unclear, particularly with an immunodeficient mouse model of human non-small cell lung cancer (NSCLC). In the present study, we investigated the anti-lung cancer effects of SEP and its underlying mechanism of action in both Lewis lung cancer (LLC)-bearing C57/BL6J mice and human NSCLC H460-bearing nude mice. Although SEP showed no inhibitory effects on tumor cells in vitro, it markedly stimulated the percentage of CD3-NK1.1(+) cells and natural killer (NK) cell cytotoxicity in the spleens of nude mice and C57/BL6J mice. In LLC-bearing mice, SEP not only inhibited tumor growth but also promoted NK-mediated cytotoxicity, the NK1.1(+) cell population, and IL-2 and IFN-γ secretion. SEP significantly suppressed H460 growth in nude mice, which was abrogated by the selective depletion of NK cells via the intraperitoneal injection of anti-asialo GM-1 antibodies. Furthermore, anti-TLR2/4 antibodies blocked both SEP and NK cell binding and SEP-induced perforin secretion. SEP-induced proliferation and IFN-γ secretion by NK cells in wild type mice were partially impaired in TLR2 or TLR4 knockout mice. These results suggest that SEP-promoted NK cytotoxicity, which was partially mediated via TLR2 and TLR4, was the main contributing factor to lung cancer inhibition in vivo and that SEP may be a potential immunotherapy candidate for the treatment of lung cancer.

Suppressing tumor growth of nasopharyngeal carcinoma by hTERTC27 polypeptide delivered through adeno-associated virus plus adenovirus vector cocktail

Nasopharyngeal carcinoma(NPC) is a metastatic carcinoma that is highly prevalent in Southeast Asia. Our laboratory has previously demonstrated that the C-terminal 27-kDa polypeptide of human telomerase reverse transcriptase (hTERTC27) inhibits the growth and tumorigenicity of human glioblastoma and melanoma cells. In this study, we investigated the antitumor effect of hTERTC27 in human C666-1 NPC cells xenografted in a nude mouse model. A cocktail of vectors comprising recombinant adeno-associated virus (rAAV) and recombinant adenovirus (rAdv) that each carry hTERTC27 (rAAV-hTERTC27 and rAdv-hTERTC27; the cocktail was abbreviated to rAAV/rAdv-hTERTC27) was more effective than either rAAV-hTERTC27 or rAdv-hTERTC27 alone in inhibiting the growth of C666-1 NPC xenografts. Furthermore, we established three tumors on each mouse and injected rAAV/rAdv-hTERTC27 into one tumor per mouse. Although hTERTC27 expression could only be detected in the injected tumors, reduced tumor growth was observed in the injected tumor as well as the uninjected tumors, demonstrating that the vector cocktail could provoke an antitumor effect on distant, metastasized tumors. Further studies showed the observed antitumor effects included inducing necrosis and apoptosis and reducing microvessel density. Together, our data suggest that the rAAV/rAdv-hTERTC27 cocktail can potently inhibit NPC tumor growth in both local and metastasized tumors and should be further developed as a novel gene therapy strategy for NPC.

Effective antitumor immunity against murine gliomas using dendritic cells transduced with hTERTC27 recombinant adenovirus

hTERTC27, a 27-kDa hTERT C-terminal polypeptide has been demonstrated to cause hTERT-positive HeLa cell apoptosis and inhibits the growth of mouse melanoma. hTERTC27 has been associated with telomere dysfunction, regulation of gene-regulated apoptosis, the cell cycle and activation of natural killer (NK) cells, but its mechanism of action is not fully understood. Here, we report that dendritic cells (DCs) transduced with hTERTC27 can increase T-cell proliferation, and augment the concentration of interleukin-2 (IL-2) and interferon-γ (IFN-γ) in the supernatants of T cells. It can also induce antigen-specific cytotoxic T lymphocytes (CTL) against glioma cells in vitro. Moreover, hTERTC27 gene-transduced DCs exhibit a very potent cytotoxicity to glioma cells in vivo. It could prolong the survival time and inhibit the growth of glioma-bearing mice. These data suggest that hTERTC27 gene-transduced DCs can efficiently enhance immunity against gliomas in vitro and in vivo.