Contribution of resident and recruited macrophages to the photodynamic intervention of colorectal tumor microenvironment

Research progress of tumor-associated macrophages in immune checkpoint inhibitor tolerance in colorectal cancer

The relevant mechanism of tumor-associated macrophages (TAMs) in the treatment of colorectal cancer patients with immune checkpoint inhibitors (ICIs) is discussed, and the application prospects of TAMs in reversing the treatment tolerance of ICIs are discussed to provide a reference for related studies. As a class of drugs widely used in clinical tumor immunotherapy, ICIs can act on regulatory molecules on cells that play an inhibitory role-immune checkpoints-and kill tumors in the form of an immune response by activating a variety of immune cells in the immune system. The sensitivity of patients with different types of colorectal cancer to ICI treatment varies greatly. The phenotype and function of TAMs in the colorectal cancer microenvironment are closely related to the efficacy of ICIs. ICIs can regulate the phenotypic function of TAMs, and TAMs can also affect the tolerance of colorectal cancer to ICI therapy. TAMs play an important role in ICI resistance, and making full use of this target as a therapeutic strategy is expected to improve the immunotherapy efficacy and prognosis of patients with colorectal cancer.

Photodynamic Therapy and Immunological View in Gastrointestinal Tumors

Gastrointestinal cancers are a specific group of oncological diseases in which the location and nature of growth are of key importance for clinical symptoms and prognosis. At the same time, as research shows, they pose a serious threat to a patient's life, especially at an advanced stage of development. The type of therapy used depends on the anatomical location of the cancer, its type, and the degree of progression. One of the modern forms of therapy used to treat gastrointestinal cancers is PDT, which has been approved for the treatment of esophageal cancer in the United States. Despite the increasingly rapid clinical use of this treatment method, the exact immunological mechanisms it induces in cancer cells has not yet been fully elucidated. This article presents a review of the current understanding of the mode of action of photodynamic therapy on cells of various gastrointestinal cancers with an emphasis on colorectal cancer. The types of cell death induced by PDT include apoptosis, necrosis, and pyroptosis. Anticancer effects are also a result of the destruction of tumor vasculature and activation of the immune system. Many reports exist that concern the mechanism of apoptosis induction, of which the mitochondrial pathway is most often emphasized. Photodynamic therapy may also have a beneficial effect on such aspects of cancer as the ability to develop metastases or contribute to reducing resistance to known pharmacological agents.

Targeting Glioblastoma-Associated Macrophages for Photodynamic Therapy Using AGuIX®-Design Nanoparticles

Glioblastoma (GBM) is the most difficult brain cancer to treat, and photodynamic therapy (PDT) is emerging as a complementary approach to improve tumor eradication. Neuropilin-1 (NRP-1) protein expression plays a critical role in GBM progression and immune response. Moreover, various clinical databases highlight a relationship between NRP-1 and M2 macrophage infiltration. In order to induce a photodynamic effect, multifunctional AGuIX^®-design nanoparticles were used in combination with a magnetic resonance imaging (MRI) contrast agent, as well as a porphyrin as the photosensitizer molecule and KDKPPR peptide ligand for targeting the NRP-1 receptor. The main objective of this study was to characterize the impact of macrophage NRP-1 protein expression on the uptake of functionalized AGuIX^®-design nanoparticles in vitro and to describe the influence of GBM cell secretome post-PDT on the polarization of macrophages into M1 or M2 phenotypes. By using THP-1 human monocytes, successful polarization into the macrophage phenotypes was argued via specific morphological traits, discriminant nucleocytoplasmic ratio values, and different adhesion abilities based on real-time cell impedance measurements. In addition, macrophage polarization was confirmed via the transcript-level expression of TNFα, CXCL10, CD-80, CD-163, CD-206, and CCL22 markers. In relation to NRP-1 protein over-expression, we demonstrated a three-fold increase in functionalized nanoparticle uptake for the M2 macrophages compared to the M1 phenotype. The secretome of the post-PDT GBM cells led to nearly a three-fold increase in the over-expression of TNFα transcripts, confirming the polarization to the M1 phenotype. The in vivo relationship between post-PDT efficiency and the inflammatory effects points to the extensive involvement of macrophages in the tumor zone.

Metallated phthalocyanines and their hydrophilic derivatives for multi-targeted oncological photodynamic therapy

BACKGROUND AND AIM

A photosensitizer (PS) delivery and comprehensive tumor targeting platform was developed that is centered on the photosensitization of key pharmacological targets in solid tumors (cancer cells, tumor vascular endothelium, and cellular and non-cellular components of the tumor microenvironment) before photodynamic therapy (PDT). Interstitially targeted liposomes (ITLs) encapsulating zinc phthalocyanine (ZnPC) and aluminum phthalocyanine (AlPC) were formulated for passive targeting of the tumor microenvironment. In previous work it was established that the PEGylated ITLs were taken up by cultured cholangiocarcinoma cells. The aim of this study was to verify previous results in cancer cells and to determine whether the ITLs can also be used to photosensitize cells in the tumor microenvironment and vasculature. Following positive results, rudimentary in vitro and in vivo experiments were performed with ZnPC-ITLs and AlPC-ITLs as well as their water-soluble tetrasulfonated derivatives (ZnPCS4 and AlPCS4) to assemble a research dossier and bring this platform closer to clinical transition.

METHODS

Flow cytometry and confocal microscopy were employed to determine ITL uptake and PS distribution in cholangiocarcinoma (SK-ChA-1) cells, endothelial cells (HUVECs), fibroblasts (NIH-3T3), and macrophages (RAW 264.7). Uptake of ITLs by endothelial cells was verified under flow conditions in a flow chamber. Dark toxicity and PDT efficacy were determined by cell viability assays, while the mode of cell death and cell cycle arrest were assayed by flow cytometry. In vivo systemic toxicity was assessed in zebrafish and chicken embryos, whereas skin phototoxicity was determined in BALB/c nude mice. A PDT efficacy pilot was conducted in BALB/c nude mice bearing human triple-negative breast cancer (MDA-MB-231) xenografts.

RESULTS

The key findings were that (1) photodynamically active PSs (i.e., all except ZnPCS4) were able to effectively photosensitize cancer cells and non-cancerous cells; (2) following PDT, photodynamically active PSs were highly toxic-to-potent as per anti-cancer compound classification; (3) the photodynamically active PSs did not elicit notable systemic toxicity in zebrafish and chicken embryos; (4) ITL-delivered ZnPC and ZnPCS4 were associated with skin phototoxicity, while the aluminum-containing PSs did not exert detectable skin phototoxicity; and (5) ITL-delivered ZnPC and AlPC were equally effective in their tumor-killing capacity in human tumor breast cancer xenografts and superior to other non-phthalocyanine PSs when appraised on a per mole administered dose basis.

CONCLUSIONS

AlPC(S4) are the safest and most effective PSs to integrate into the comprehensive tumor targeting and PS delivery platform. Pending further in vivo validation, these third-generation PSs may be used for multi-compartmental tumor photosensitization.

Trojan horse monocyte-mediated delivery of conjugated polymer nanoparticles for improved photodynamic therapy of glioblastoma

Aim: To assess monocyte-based delivery of conjugated polymer nanoparticles (CPNs) for improved photodynamic therapy (PDT) in glioblastoma (GBM). Materials & methods: Human monocyte cells (THP-1) and murine monocytes isolated from bone marrow (mBMDMs) were employed as stealth CPN carriers to penetrate into GBM spheroids and an orthotopic model of the tumor. The success of PDT, using this cell-mediated targeting strategy, was determined by its effect on the spheroids. Results: CPNs did not affect monocyte viability in the absence of light and did not show nonspecific release after cell loading. Activated monocytes incorporated CPNs in a higher proportion than monocytes in their naive state, without a loss of cellular functionality. In vitro PDT efficacy using cell-mediated delivery was superior to that using non vehiculized CPNs. Conclusion: CPN-loaded monocytes could efficiently deliver CPNs into GBM spheroids and the orthotopic model. Improved PDT in spheroids was confirmed using this delivery strategy.

Recapitulation of Hypoxic Tumor-stroma Microenvironment to Study Photodynamic Therapy Implications

Tumor microenvironment (TME) is a dynamic ecosystem where fibroblasts are recruited in order to provide a niche to support growth and, in some extent, to promote therapeutic resistance. However, the role of fibroblasts in stimulating or impairing photodynamic therapy (PDT) outcome has not yet been fully addressed. PDT is based on interactions between light, oxygen and photosensitizer, leading to phototoxic reactions that culminate in cell death. In this study, we demonstrated the consequences of a hypoxic stromal phenotype on tumor mass for exploring PDT response. We mimicked TME complexity implementing colon cancer cells and fibroblasts 3D cultures called spheroids. Using hypoxia reporting lines, we verified that homotypic spheroids exhibited a size-dependent transcriptional HIF-1 activity. When cocultured, fibroblasts were localized in the hypoxic core. In homotypic stromal spheroids, the distribution of the endogenous photosensitizer PpIX was homogeneous while decreased in hypoxic areas of tumor 3D cultures. When monocultured, fibroblasts were more efficient to produce PpIX from its prodrug Me-ALA. Interestingly, the cross talk between cancer cells and fibroblasts attenuated PpIX accumulation and conferred tumor PDT resistance when compared to homotypic 3D cultures. Overall, our data suggest that stroma and tumor act in an integrated, reciprocal fashion which could ultimately influence on therapeutic response.

Tumor cell death in orthotopic breast cancer model by NanoALA: a novel perspective on photodynamic therapy in oncology

Aim: Nano-5-aminolevulic acid (NanoALA)-mediated photodynamic therapy (PDT), an oil-in-water polymeric nanoemulsion of ALA, was evaluated in a murine model of breast cancer. Materials & methods: Analysis of ALA-derived protoporphyrin IX production and acute toxicity test, biocompatibility and treatment efficacy, and long-term effect of NanoALA-PDT on tumor progression were performed. Results: The nanoformulation favored the prodrug uptake by tumor cells in a shorter time (1.5 h). As a result, the adverse effects were negligible and the response rates for primary mammary tumor control were significantly improved. Tumor progression was slower after NanoALA-PDT treatment, providing longer survival. Conclusion: NanoALA is a good proactive drug candidate for PDT against cancer potentially applied as adjuvant/neoadjuvant intervention strategy for breast cancer.

Inhibition of IDO leads to IL-6-dependent systemic inflammation in mice when combined with photodynamic therapy

It was previously reported that the activation of antitumor immune response by photodynamic therapy (PDT) is crucial for its therapeutic outcome. Excessive PDT-mediated inflammation is accompanied by immunosuppressive mechanisms that protect tissues from destruction. Thus, the final effect of PDT strongly depends on the balance between the activation of an adoptive arm of immune response and a range of activated immunosuppressive mechanisms. Here, with flow cytometry and functional tests, we evaluate the immunosuppressive activity of tumor-associated myeloid cells after PDT. We investigate the antitumor potential of PDT combined with indoleamine 2,3-dioxygenase 1 (IDO) inhibitor in the murine 4T1 and E0771 orthotopic breast cancer models. We found that the expression of IDO, elevated after PDT, affects the polarization of T regulatory cells and influences the innate immune response. Our results indicate that, depending on a therapeutic scheme, overcoming IDO-induced immunosuppressive mechanisms after PDT can be beneficial or can lead to a systemic toxic reaction. The inhibition of IDO, shortly after PDT, activates IL-6-dependent toxic reactions that can be diminished by the use of anti-IL-6 antibodies. Our results emphasize that deeper investigation of the physiological role of IDO, an attractive target for immunotherapies of cancer, is of great importance.

Secretome profiling of heterotypic spheroids suggests a role of fibroblasts in HIF-1 pathway modulation and colorectal cancer photodynamic resistance

PURPOSE

Previous analyses of the tumor microenvironment (TME) have resulted in a concept that tumor progression may depend on interactions between cancer cells and its surrounding stroma. An important aspect of these interactions is the ability of cancer cells to modulate stroma behavior, and vice versa, through the action of a variety of soluble mediators. Here, we aimed to identify soluble factors present in the TME of colorectal cancer cells that may affect relevant pathways through secretome profiling.

METHODS

To partially recapitulate the TME and its architecture, we co-cultured colorectal cancer cells (SW480, TC) with stromal fibroblasts (MRC-5, F) as 3D-spheroids. Subsequent characterization of both homotypic (TC) and heterotypic (TC + F) spheroid secretomes was performed using label-free liquid chromatography-mass spectrometry (LC-MS).

RESULTS

Through bioinformatic analysis using the NCI-Pathway Interaction Database (NCI-PID) we found that the HIF-1 signaling pathway was most highly enriched among the proteins whose secretion was enhanced in the heterotypic spheroids. Previously, we found that HIF-1 may be associated with resistance of colorectal cancer cells to photodynamic therapy (PDT), an antitumor therapy that combines photosensitizing agents, O₂ and light to create a harmful photochemical reaction. Here, we found that the presence of fibroblasts considerably diminished the sensitivity of colorectal cancer cells to photodynamic activity. Although the biological significance of the HIF-1 pathway of secretomes was decreased after photosensitization, this decrease was partially reversed in heterotypic 3D-spheroids. HIF-1 pathway modulation by both PDT and stromal fibroblasts was confirmed through expression assessment of the HIF-target VEGF, as well as through HIF transcriptional activity assessment.

CONCLUSION

Collectively, our results delineate a potential mechanism by which stromal fibroblasts may enhance colorectal cancer cell survival and photodynamic treatment resistance via HIF-1 pathway modulation.

Specific tumor-derived CCL2 mediated by pyruvate kinase M2 in colorectal cancer cells contributes to macrophage recruitment in tumor microenvironment

Development of colorectal cancer has been considered as a result of imbalance of pro- and anti-inflammatory intestinal microenvironment accompanied by macrophage recruitment. Despite macrophages are implicated in remodeling tumor microenvironment, the mechanism of macrophage recruitment is not fully elucidated yet. In this study, we reported clinical association of highly expressed pyruvate kinase M2 in colorectal cancer with macrophage attraction. The conditioned medium from Caco-2 and HT-29 cells with depleted pyruvate kinase M2 dramatically reduced macrophage recruitment, which is reversed by addition of, a critical chemotaxis factor to macrophage migration, rCCL2. Silencing of endogenous pyruvate kinase M2 markedly decreased CCL2 expression and secretion by real-time quantitative polymerase chain reaction and enzyme-linked immunosorbent assay. Endogenous pyruvate kinase M2 interacted with p65 and mediated nuclear factor-κB signaling pathway and mainly regulated phosphorylation of Ser276 on p65 nuclear factor-κB. In addition, inhibition of macrophage recruitment caused by pyruvate kinase M2 silencing was rescued by ectopic expression of p65. Interestingly, pyruvate kinase M2 highly expressed in colorectal cancer tissue, which is correction with macrophage distribution. Taken together, we revealed a novel mechanism of pyruvate kinase M2 in promoting colorectal cancer progression by recruitment of macrophages through p65 nuclear factor-κB-mediated expression of CCL2.

Bimodal Targeting Using Sulfonated, Mannosylated PEI for Combined Gene Delivery and Photodynamic Therapy

Photodynamic therapy (PDT) and gene delivery have both been used to target both cancer cells and tumor-associated macrophages (TAMs). Given the complex nature of tumor tissue, there could be merit in combining these strategies simultaneously. In this study, we developed a bimodal targeting approach to both cancer cells and macrophages, employing materials conducive to both gene delivery and PDT. Polymers libraries were created that consisted of cationic polyethyleneimine (PEI) conjugated to the photosensitizer pyropheophorbide-a, with sulfonation (to target selectin-expressing cells) and mannosylation (to target TAMs). Polyplexes, consisting of these polymers electrostatically bound to DNA, were analyzed for transfection efficacy and cytotoxicity toward epithelial cells and macrophages to assess dual-targeting. This study provides preliminary proof of principle for using modified PEI for targeted gene delivery and PDT.

Loss of free fatty acid receptor 2 enhances colonic adenoma development and reduces the chemopreventive effects of black raspberries in ApcMin/+ mice

We previously showed that black raspberries (BRBs) have beneficial effects in human colorectal cancer and a mouse model of colorectal cancer (Apc^Min/+). The current study investigated the role of free fatty acid receptor 2 (FFAR2) in colon carcinogenesis and whether the FFAR2 signaling pathway contributes to BRB-mediated chemoprevention in mice. FFAR2 (also named GPR43) is a member of the G-protein-coupled receptor family that is expressed in leukocytes and colon. Apc^Min/+ and Apc^Min/+-FFAR2^-/- mice were given a control diet or the control diet supplemented with 5% BRBs for 8 weeks. FFAR2 deficiency promoted colonic polyp development, with 100% incidence and increased polyp number and size. The Apc^Min/+ mice developed colonic tubular adenoma, whereas the Apc^Min/+-FFAR2^-/- mice developed colonic tubular adenoma with high-grade dysplasia. FFAR2 deficiency also enhanced the cAMP-PKA-CREB-HDAC pathway, downstream of FFAR2 signaling, and increased activation of the Wnt pathway, and raised the percentage of GR-1⁺ neutrophils in colonic lamina propria (LP) and increased infiltration of GR-1⁺ neutrophils into colonic polyps. BRBs suppressed colonic polyp development and inhibited the cAMP-PKA-CREB-HDAC and Wnt pathways in the Apc^Min/+ mice but not the Apc^Min/+-FFAR2^-/- mice. They also increased the percentage of GR-1⁺ neutrophils and cytokine secretion in colonic LP and decreased the infiltration of GR-1⁺ neutrophils and IL-1β expression in colon polyps of Apc^Min/+ mice but not Apc^Min/+-FFAR2^-/- mice. These results suggest that loss of FFAR2 drives colon tumorigenesis and that BRBs require functional FFAR2 to be chemopreventive. BRBs have the potential to modulate the host immune system, thereby enhancing the antitumor immune microenvironment.

Targeting Antitumor Immune Response for Enhancing the Efficacy of Photodynamic Therapy of Cancer: Recent Advances and Future Perspectives

Photodynamic therapy (PDT) is a minimally invasive therapeutic strategy for cancer treatment, which can destroy local tumor cells and induce systemic antitumor immune response, whereas, focusing on improving direct cytotoxicity to tumor cells treated by PDT, there is growing interest in developing approaches to further explore the immune stimulatory properties of PDT. In this review we summarize the current knowledge of the innate and adaptive immune responses induced by PDT against tumors, providing evidence showing PDT facilitated-antitumor immunity. Various immunotherapeutic approaches on different cells are reviewed for their effectiveness in improving the treatment efficiency in concert with PDT. Future perspectives are discussed for further enhancing PDT efficiency via intracellular targetable drug delivery as well as optimized experimental model development associated with the study of antitumor immune response.

A three-dimensional co-culture system to investigate macrophage-dependent tumor cell invasion

Macrophages infiltrate cancers and promote progression to invasion and metastasis. To directly examine tumor-associated macrophages (TAMs) and tumor cells interacting and co-migrating in a three-dimensional (3D) environment, we have developed a co-culture model that uses a PyVmT mouse mammary tumor-derived cell line and mouse bone marrow-derived macrophages (BMM). The Py8119 cell line was cloned from a spontaneous mammary tumor in a Tg(MMTV:LTR-PyVmT) C57Bl/6 mouse and these cells form 3-dimensional (3D) spheroids under conditions of low adhesion. Co-cultured BMM infiltrate the Py8119 mammospheres and embedding of the infiltrated mammospheres in Matrigel leads to subsequent invasion of both cell types into the surrounding matrix. This physiologically relevant co-culture model enables examination of two critical steps in the promotion of invasion and metastasis by BMM: 1) macrophage infiltration into the mammosphere and, 2) subsequent invasion of macrophages and tumor cells into the matrix. Our methodology allows for quantification of BMM infiltration rates into Py8119 mammospheres and demonstrates that subsequent tumor cell invasion is dependent upon the presence of infiltrated macrophages. This method is also effective for screening macrophage motility inhibitors. Thus, we have developed a robust 3D in vitro co-culture assay that demonstrates a central role for macrophage motility in the promotion of tumor cell invasion.

Curative effect of the recent photofrin photodynamic adjuvant treatment on young patients with advanced colorectal cancer

Advanced colorectal cancer has a high mortality rate and conventional treatments have poor therapeutic effects. The aim of the present study was to analyze the recent curative effect and adverse reaction of photofrin photodynamic adjuvant treatment on young patients with advanced colorectal cancer. A total of 23 patients with advanced colorectal cancer who had accepted semiconductor laser photodynamic adjuvant treatment were selected as the observation group. In addition, 30 patients who had accepted concurrent radiotherapy and chemotherapy during the same period served as the control group. The observation group received photofrin (2 mg/kg) intravenously in 100 ml of 5% glucose, followed by the introduction of the endoscopic optical fiber to deliver laser radiation with an intensity of 630 nm wavelength pulse power. After 2 days, necrotic tissues were removed and irradiation of the original or new tumor lesions was performed and necrotic tissues were removed. The total effective rate and survival time was higher and the length of hospital stay was shorter in the observation group in comparison with the control group. The differences were statistically significant (P<0.05). The number of patients in the control and observation groups with symptoms of hematochezia, change in bowel habit, intestinal stimulation and incomplete intestinal obstruction were reduced. Additionally, the reduced ratio of the observation group was significantly increased in comparison with the control group (P<0.05). The adverse reaction rate of the observation group was lower than that of the control group and this difference was also statistically significant (P<0.05). In conclusion, use of photodynamic treatment for young patients with advanced colorectal cancer can effectively improve the clinical symptoms and reduce complications.