A Macrophages-Enriched Head and Neck Tumor Spheroid Model to Study Foslip® Behavior in Tumor Microenvironment

Purpose

The tumor microenvironment (TME) is composed of various stromal components, including immune cells such as tumor-associated macrophages (TAMs), which play a crucial role in cancer initiation and progression. TAMs can exhibit either a tumor-suppressive M1 or a tumor-promoting M2 phenotype. First, we aimed to develop a 3D human heterotypic model consisting of head and neck squamous cell carcinoma (HNSCC) cells and different subtypes of macrophages to replicate the interactions between immune cells and cancer cells. We further investigated the behavior of Foslip®, a liposomal formulation of temoporfin, using a macrophage-enriched 3D model.

Methods

Monocytes were differentiated into M1 and M2 macrophages, which represent two distinct subtypes. Following histological and molecular characterization, these macrophages were used to establish a 3D spheroid model of HNSCC enriched with either polarized macrophages or conditioned media. Flow cytometry and fluorescence microscopy were used to assess the accumulation and distribution of Foslip®. The cytotoxic effect of Foslip®-mediated photodynamic therapy (PDT) was evaluated using flow cytometry.

Results

We developed heterotypic spheroids characterized by a mixed phenotype of evenly distributed macrophages. In this 3D co-culture model, both M1 and M2 macrophages showed significantly higher accumulation of Foslip® compared to the cancer cells. Although this differential accumulation did not drastically affect the overall PDT efficiency, spheroids generated with conditioned media exhibited a significant enhancement in photo-induced cell death, suggesting that the microenvironment could modulate the response to Foslip®-PDT.

Conclusion

3D models of HNSCC cells and macrophages provide valuable insights into the complex response of HNSCC cells to PDT using Foslip® in vitro. This model can be used to screen immunomodulatory nanomedicines targeting TAMs in solid head and neck tumors, either alone or in combination with standard therapies.

Foscan and foslip based photodynamic therapy in osteosarcoma in vitro and in intratibial mouse models

Current osteosarcoma therapies cause severe treatment-related side effects and chemoresistance, and have low success rates. Consequently, alternative treatment options are urgently needed. Photodynamic therapy (PDT) is a minimally invasive, local therapy with proven clinical efficacy for a variety of tumor types. PDT is cytotoxic, provokes anti-vascular effects and stimulates tumor cell targeting mechanisms of the immune system and, consequently, has potential as a novel therapy for osteosarcoma patients. This study investigated the uptake and the dark- and phototoxicity and cytotoxic mechanisms of the photosensitizer (PS) 5,10,15,20-tetrakis(meta-hydroxyphenyl) chlorine (mTHPC, Foscan) and a liposomal mTHPC formulation (Foslip) in the human 143B and a mouse K7M2-derived osteosaroma cell line (K7M2L2) in vitro. Second, the tumor- and metastasis-suppressive efficacies of mTHPC formulations based PDT and associated mechanisms in intratibial, metastasizing osteosarcoma mouse models (143B/SCID and syngeneic K7M2L2/BALB/c) were studied. The uptake of Foscan and Foslip in vitro was time- and dose-dependent and resulted in mTHPC and light dose-dependent phototoxicity associated with apoptosis. In vivo, the uptake of both i.v. administered mTHPC formulations was higher in tumor than in healthy control tissue. PDT caused significant (Foscan p < 0.05, Foslip p < 0.001) tumor growth inhibition in both models. A significant (Foscan p < 0.001, Foslip p < 0.001) immune system-dependent suppression of lung metastasis was only observed in the K7M2L2/BALB/c model and was associated with a marked infiltration of T-lymphocytes at the primary tumor site. In conclusion, mTHPC-based PDT is effective in clinically relevant experimental osteosarcoma and suppresses lung metastasis in immunocompetent mice with beneficial effects of the liposomal mTHPC formulation Foslip.

Photochemical internalization (PCI)-mediated enhancement of bleomycin cytotoxicity by liposomal mTHPC formulations in human head and neck cancer cells

BACKGROUND AND OBJECTIVE

Photodynamic therapy (PDT) with photosensitizers that locate in endocytic vesicles of cancer cells can be exploited to promote the intracellular release of anticancer drugs entrapped in endolysosomal vesicles. This new approach is commonly referred to as Photochemical Internalization (PCI). Here we report on the PCI effects of three different formulations (Foscan, Foslip, and Fospeg) of the clinically approved photosensitizer, meta-tetrahydroxyphenyl chlorin (mTHPC) on the anticancer drug bleomycin (BLM) in the head and neck cancer cell lines.

MATERIALS AND METHODS

Uptake and localization of Foscan, Foslip, and Fospeg in head and neck cancer cells were evaluated by fluorescence spectrophotometry and fluorescence microscopy. Photodynamic efficacy of Foscan, Foslip, and Fospeg were compared with cell proliferation assay. Moreover, PCI effects of Foscan, Foslip, and Fospeg on BLM were compared using protocols in which PDT was applied after or before BLM treatment.

RESULTS

Cellular uptake of Foscan, Foslip, and Fospeg increased in a dose-dependent fashion with consistent higher uptakes of Foslip and Fospeg than Foscan. Fluorescence microscopy showed diffuse intracellular localization pattern for Foscan, Foslip, and Fospeg similar to that of a specific ER probe. However, the subcellular localization pattern of the Rhodamine-labelled same type of pegylated liposomes as Fospeg was similar to that of a specific endolysosomal probe, suggesting that Fospeg uptake appeared to initially proceed via endolysosomal trafficking. Foscan, Foslip, and Fospeg showed no apparent PCI-mediated cytotoxicity when PDT was performed after BLM treatment. However, significantly increased cytotoxicity of BLM (P < 0.05) was observed for both Foslip and Fospeg when PDT was performed before BLM treatment. The observed differences of PCI-mediated cytotoxicity between these two timing protocols appears to be related to the differential intracellular trafficking and localization of Foscan, Foslip, and Fospeg.

CONCLUSION

Liposomal formulations of mTHPC may be candidates for developing mTHPC-based PCI protocols to enhance the efficacy of anticancer drugs entrapped in endolysosomal vesicles.