Pulsed Photothermal Therapy of Solid Tumors as a Precondition for Immunotherapy

Photothermal therapy (PTT) refers to the use of plasmonic nanoparticles to convert electromagnetic radiation in the near infrared region to heat and kill tumor cells. Continuous wave lasers have been used clinically to induce PTT, but the treatment is associated with heat-induced tissue damage that limits usability. Here, the engineering and validation of a novel long-pulsed laser device able to induce selective and localized mild hyperthermia in tumors while reducing the heat affected zone and unwanted damage to surrounding tissue are reported. Long-pulsed PTT induces acute necrotic cell death in heat affected areas and the release of tumor associated antigens. This antigen release triggers maturation and stimulation of CD80/CD86 in dendritic cells in vivo that primes a cytotoxic T cell response. Accordingly, long-pulsed PTT enhances the therapeutic effects of immune checkpoint inhibition and increases survival of mice with bladder cancer. Combined, the data promote long-pulsed PTT as a safe and effective strategy for enhancing therapeutic responses to immune checkpoint inhibitors while minimizing unwanted tissue damage.

Internalization and trafficking of CSPG-bound recombinant VAR2CSA lectins in cancer cells

Proteoglycans are proteins that are modified with glycosaminoglycan chains. Chondroitin sulfate proteoglycans (CSPGs) are currently being exploited as targets for drug-delivery in various cancer indications, however basic knowledge on how CSPGs are internalized in tumor cells is lacking. In this study we took advantage of a recombinant CSPG-binding lectin VAR2CSA (rVAR2) to track internalization and cell fate of CSPGs in tumor cells. We found that rVAR2 is internalized into cancer cells via multiple internalization mechanisms after initial docking on cell surface CSPGs. Regardless of the internalization pathway used, CSPG-bound rVAR2 was trafficked to the early endosomes in an energy-dependent manner but not further transported to the lysosomal compartment. Instead, internalized CSPG-bound rVAR2 proteins were secreted with exosomes to the extracellular environment in a strictly chondroitin sulfate-dependent manner. In summary, our work describes the cell fate of rVAR2 proteins in tumor cells after initial binding to CSPGs, which can be further used to inform development of rVAR2-drug conjugates and other therapeutics targeting CSPGs.

Abstract 5229: Expression and regulation of chondroitin sulfate in prostate cancer

Increased levels of chondroitin sulfate (CS) glycosaminoglycans (GAGs) in prostate cancer (PC) have been observed for more than three decades. In 1984, De Klerk et al. noted that hyperplastic and cancerous prostate contained elevated levels of CS while other GAGs, like heparin sulfate (HS), were decreased. Chondroitin sulfate-modified proteoglycans (CSPGs), such as versican or tomoregulin (TENB2), have been promoted as PC progression markers. They have been associated with cell attachment to the matrix, the metastatic phenotype, disease progression, and androgen independence. Functionally, pericellular enrichment of CSPGs in the PC microenvironment promotes cell motility. Our team has discovered that human tumors display high levels of a specific highly sulfate type of CS normally restricted to placental and fetal tissue compartment. This "oncofetal" CS (ofCS) GAG can be conveniently detected and targeted using recombinant CS-binding VAR2CSA (rVAR2) lectins, derived from the malaria parasite Plasmodium falciparum. Recently, we identified chondroitin sulfate biosynthesis as being controlled by androgens in PC, modulating expression of the CHST11 and CHST13 carbon-4 GalNAc sulfotransferases. We established that these enzymes are under direct control of the androgen receptor (AR), regulating synthesis of the cancer-associated ofCS-modification on CSPGs. Glycosylation has a key role in many important biologic processes in cancer including cell differentiation. We identified CHST11 to be highly increased in high-risk neuroendocrine prostate cancer (NEPC) both in vitro, in vivo, and in situ. Moreover, cells that expressed neuroendocrine markers showed higher level of sulfation and ofCS. Our work reveals that alterations in GAG signatures regulated by AR might be responsible for progression neuroendocrine differentiation in prostate cancer. The prostate is an abundant secretor of PGs, and tumor-specific alterations in GAG signatures such as ofCS therefore constitute an untapped reservoir of potential biomarkers to be exploited as therapeutic targets.

Citation Format: Nader Al Nakouzi, Chris Kedong Wang, Irina Nelepcu, Coralie Crouzit, Noushin Nabavi, Amal Almami, Htoo Zarni Oo, Thomas Mandel Clausen, Tobias Gustavsson, Ali Salanti, Mads Daugaard. Expression and regulation of chondroitin sulfate in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5229.