 of animals, there have only been a handful of deepsea sharks recorded as albino.
“After looking through some literature, I couldn't find anything that reported albinism in the lanternshark family, Etmopteridae, so it was a new record. We can't say for certain how many sharks are albino because the deepsea is so understudied, but it is a rare occurrence,” says Dr. Finucci.
Lucifer’s dogfish is one of the smallest shark species in New Zealand, growing to just 50cm. They are found throughout the western Pacific Ocean living at depths up to 1000m.
Lucifer's dogfish is one of the smallest shark species in New Zealand and is found at depths up to 1000m. [Photo: Brit Finucci, NIWA] Lucifer’s dogfish, like most sharks in the lanternshark family are bioluminescent, meaning they can produce their own light. The albino shark examined by Dr. Finucci still had photophore organs suggesting that it could produce its own light.
She says there are several theories that explain why bioluminescent sharks produce light.
“Each shark species has its own unique pattern of bioluminescence, so it’s thought that bioluminescence is used for intra-species communication, so communicating among its own species. There's been speculations too, that it might be used for counter illumination or hiding from predators, and attracting prey,” she explains.
Remarkably, the albino shark was caught in 1984 by a research vessel at Cape Palliser in the Wairarapa. It was sent to the Auckland War Memorial Museum where it has remained unstudied for 36 years.
Dr. Finucci thinks that a general lack of research in deepwater sharks, as well as the considerable amount of time and resources required to process museum collections are possible reasons why the shark has never been studied. She says that the finding highlights the importance of museum collections and their ongoing role in science.
3Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada.
Tumor antigens and innate signals are vital considerations in developing new therapeutic or prophylactic antitumor vaccines. The role or requirement of intact tumor cells in the development of an effective tumor vaccine remains incompletely understood. This study reveals the mechanism by which tumor cell–derived microparticles (T-MP) can act as a cell-free tumor vaccine. Vaccinations with T-MPs give rise to prophylactic effects against the challenge of various tumor cell types, while T-MP–loaded dendritic cells (DC) also exhibit therapeutic effects in various tumor models. Such antitumor effects of T-MPs are perhaps attributable to their ability to generate immune signaling and to represent tumor antigens. Mechanically, T-MPs effectively transfer DNA fragments to DCs, leading to type I IFN production through the cGAS/STING-mediated DNA-sensing pathway. In turn, type I IFN promotes DC maturation and presentation of tumor antigens to T cells for antitumor immunity. These findings highlight a novel tumor cell-free vaccine strategy with potential clinical applications. Cancer Immunol Res; 3(2); 196–205. ©2014 AACR.
Success of a tumor vaccine lies in its ability to provide both tumor antigens and immunostimulatory signals to antigen-presenting cells (APC), leading to tumor-specific T-cell immune responses. Despite the continual discovery of new tumor antigens, using tumor cells as anticancer vaccines remains an attractive strategy, because it offers a broader repertoire of tumor-associated antigens to reduce the possibility of immune escape and development of resistance. Furthermore, the immunogenicity of whole tumor-cell vaccines can be augmented by modifying tumor cells with expression of GM-CSF or other immunostimulatory genes to generate improved antitumor T-cell immunity. To date, autologous and allogeneic whole tumor-cell–based vaccines have been intensely studied in clinical trials in patients with melanoma, renal cell and hepatocellular carcinomas, lung, prostate, breast, colorectal, cervical, pancreatic, or ovarian cancer (1–3). However, there is evidence that tumor cell–derived cytokines (e.g., VEGF, IL10, and TGFβ) and biologic factors (e.g., galectin-1, indoleamine 2,3-dioxygenase, lipid droplets) suppress dendritic cell (DC) maturation and T-cell activation, thus limiting the efficacy and efficiency of whole cell–based vaccination (4, 5). Therefore, a vaccine platform that can simultaneously deliver multiple tumor antigens and immunostimulatory signals to DCs remains to be developed.
Exosomes are small vesicles (60–100 nm) that are released from the cell upon fusion of multivesicular bodies with the plasma membrane (6). Exosomes are secreted by multiple cell types including tumor cells, and it is likely that tumor-released exosomes contain tumor-specific antigens expressed in the parental tumor cells, representing a new cell-free source of shared tumor antigens for in vivo immune priming or tumor vaccine design (7). Indeed, vaccination with tumor cell–derived exosomes or exosome-pulsed DCs was able to induce CD8+ T-cell–dependent antitumor effects in both mice and humans (7, 8). However, many reports also suggest that tumor cell–derived exosomes can confer immune suppression through different mechanisms including downregulation of DC maturation, raising concerns about the use of exosomes as tumor vaccine (9).
In addition to exosomes, tumor cells also secrete other types of vesicles of different sizes (10, 11). In response to stress, tumor cells change their cytoskeleton, leading to encapsulation of cytosolic contents by cellular membrane to form vesicles that are subsequently released into the extracellular space. These specialized subcellular vesicles with a diameter of 100 to 1,000 nm are called microparticles, which are different from exosomes in size, membrane structure, and contents (12). Recently, we have demonstrated that tumor cell–derived microparticles (T-MP) can serve as a safe and efficient carrier to deliver chemotherapeutic drugs to tumor cells, whereas their capacity as a novel vaccine platform remains to be determined (13). In another study, we demonstrated that microparticles released by Listeria monocytogenes–infected macrophages could transfer L. monocytogenes antigens to DCs, leading to the induction of protective adaptive immune responses against the bacteria (14), implicating the potential of microparticles as a vehicle for antigen delivery and DC targeting. In the present study, we provide evidence that T-MPs may represent a novel tumor vaccine due to their possession of both tumor antigens and innate DNA signals.
Female BALB/c, BALB/c-nude mice, and C57BL/6 mice (6–8 weeks old) were purchased from Centre of Medical Experimental Animals of Hubei Province (Wuhan, China). All animal experiments were approved by the Animal Care and Use Committee of Tongji Medical College. Mouse H22 hepatocarcinoma, B16 melanoma, and CT26 colon carcinoma tumor cell lines were purchased from the China Centre for Type Culture Collection (CCTCC), and cultured according to the manufacturer's guidelines. All cell lines were tested and determined to be free of Mycoplasma and other rodent pathogens by the CCTCC; no other authentication assay was performed.
Tumor cells were exposed to ultraviolet irradiation (300 J/m2) for 1 hour, and 12 hours later, supernatants were used for microparticle isolation as described previously (13). Briefly, supernatants were centrifuged at 1,000 g for 10 minutes to remove whole cells and then centrifuged for 2 minutes at 14,000 g to remove debris. The supernatant was further centrifuged for 60 minutes at 14,000 g to pellet microparticles. The pellets were washed three times and resuspended in culture medium for the subsequent experiments.
Exosomes were isolated as described (8). Briefly, H22 tumor cells were cultured for 48 hours, and the supernatants were collected and centrifuged (4°C) at 500 g for 10 minutes, 14,000 g for 30 minutes, and exosomes were then harvested by centrifugation at 100,000 g for 70 minutes. The exosome pellet was suspended in 20 mL of PBS and collected by ultracentrifugation as described above. Tumor-cell lysates were prepared by subjecting 1 × 107/mL H22 tumor cells in PBS to three cycles of rapid freezing in liquid nitrogen and thawing at 37°C. The lysates were centrifuged at 2,000 g for 10 minutes to remove cellular debris.
For the H22 or CT26 tumor models, BALB/c mice were immunized three times in the lower left flank with T-MPs or PBS by s.c. injection on days −14, −13, and −7. On day 0, mice were challenged with H22 or CT26 tumor cells (3 × 105 cells/mouse) in the contralateral right flank. Palpable tumors were measured by calipers, and tumor volume was calculated according to the formula: volume = (length × width2)/2, where length and width are measured in millimeters. For the B16 melanoma tumor model, C57BL/6 mice received s.c. injection of 3 × 105 B16 melanoma cells after immunization with B16-MPs as described above. In the metastasis model, C57BL/6 mice were i.v injected with 1 × 105 B16 melanoma cells after immunization with B16-MPs, and 21 days later, mice were sacrificed and the black melanoma nodules on the lungs were assayed.
For the immune-deficient model, nude mice were immunized with H22-MPs or PBS and then challenged with H22 tumor cells. In lymphocyte-depletion experiments, mice were injected i.p. with 0.1-mg anti-CD4 (clone GK1.5), anti-CD8 (clone 53-6.7), or anti-asialo GM1 (eBioscience) antibody at days −1, 2, 5, and 8 before/after tumor inoculation. Tumor size was measured every