Inhibitory Effects and Gene Expression Analysis of Chemotherapeutic Photodynamic Therapy by using a Liposomally Formulated Indocyanine Green Derivative

Encapsulation of photosensitizer worsen cell responses after photodynamic therapy protocol and polymer micelles act as biomodulators on their own

Photodynamic therapy (PDT) is a photochemical therapeutic modality used clinically for dermatological, ophthalmological and oncological applications. Pheo a was used as a model photosensitizer, either in its free form or encapsulated within poly(ethylene oxide)-block-poly(ε-caprolactone) (PEO-PCL) polymer micelles. Block copolymer micelles are water-soluble biocompatible nanocontainers with great potential for delivering hydrophobic drugs. Empty PEO-PCL micelles were also tested throughout the experiments. The goal was to conduct an in vitro investigation into human colorectal tumor HCT-116 cellular responses induced by free and encapsulated Pheo a in terms of cell architecture, plasma membrane exchanges, mitochondrial function, and metabolic disturbances. In a calibrated PDT protocol, encapsulation enhanced Pheo a penetration (flow cytometry, confocal microscopy) and cell death (Prestoblue assay), causing massive changes to cell morphology (SEM) and cytoskeleton organization (confocal), mitochondrial dysfunction and loss of integrity (TEM), rapid and massive ion fluxes across the plasma membrane (ICP-OES, ion chromatography), and metabolic alterations, including increased levels of amino acids and choline derivatives (1H NMR). The detailed investigation provides insights into the multifaceted effects of encapsulated Pheo-PDT, emphasizing the importance of considering both the photosensitizer and its delivery system in understanding therapeutic outcomes. The study also raises questions as to the broader impact of empty nanovectors per se, and encourages a more comprehensive exploration of their biological effects.

Photodynamic therapy with paclitaxel-encapsulated indocyanine green-modified liposomes for breast cancer

Background

Photodynamic therapy (PDT) involves the administration of a photosensitizing agent and irradiation of light at an excitation wavelength that damages tumor cells without causing significant damage to normal tissue. We developed indocyanine green (ICG)-modified liposomes in which paclitaxel (PTX) was encapsulated (ICG-Lipo-PTX). ICG-Lipo-PTX accumulates specifically in tumors due to the characteristics of the liposomes. The thermal and photodynamic effects of ICG and the local release of PTX by irradiation are expected to induce not only antitumor effects but also cancer immunity. In this study, we investigated the antitumor effects of ICG-Lipo-PTX in breast cancer.

Methods

The antitumor effects of ICG-Lipo-PTX were examined in xenograft model mice subcutaneously implanted with KPL-1 human breast cancer cells. ICG-Lipo-PTX, ICG-Lipo, or saline was administered intraperitoneally, and the fluorescence intensity was measured with a fluorescence imaging system (IVIS). Intratumor temperature, tumor volume, and necrotic area of tumor tissue were also compared. Next, we investigated the induction of cancer immunity in an allogeneic transplantation model in which BALB-MC mouse breast cancer cells were transplanted subcutaneously in the bilateral inguinal region. ICG-Lipo-PTX was administered intraperitoneally, and PDT was performed on only one side. The fluorescence intensity measured by IVIS and the bilateral tumor volumes were compared. Cytokine secretory capacity was also evaluated by ELISPOT assay using splenocytes.

Results

In the xenograft model, the fluorescence intensity and temperature during PDT were significantly higher with ICG-Lipo-PTX and ICG-Lipo in tumor areas than in nontumor areas. The fluorescence intensity in the tumor area was reduced to the same level as that in the nonirradiated area after two times of irradiation. Tumor growth was significantly reduced and the percentage of necrotic area in the tumor was higher after PDT in the ICG-Lipo-PTX group than in the other groups. In the allograft model, tumor growth on day 14 in the ICG-Lipo-PTX group was significantly suppressed not only on the PDT side but also on the non-PDT side. In addition, the secretion of interferon-γ and interleukin-2 was enhanced, whereas that of interleukin-10 was suppressed, in the ICG-Lipo-PTX group.

Conclusion

The PDT therapy with ICG-Lipo-PTX may be an effective treatment for breast cancer.

Indocyanine green conjugated phototheranostic nanoparticle for photodiagnosis and photodynamic reaciton

BACKGROUND

Phototheranostics represents a highly promising paradigm for cancer therapy, although selecting an appropriate optical imager and sensitizer for clinical use remains challenging.

METHODS

Liposomally formulated phospholipid-conjugated indocyanine green, denoted as LP-iDOPE, was developed as phototheranostic nanoparticle and its cancer imaging-mediated photodynamic reaction, defined as the immune response induced by photodynamic and photothermal effects, was evaluated with a near-infrared (NIR)-light emitting diode (LED) light irradiator.

RESULTS

Using in vivo NIR fluorescence imaging, we demonstrated that LP-iDOPE was selectively delivered to tumor sites with high accumulation and a long half-life. Following low-intensity NIR-LED light irradiation on the tumor region of LP-iDOPE accumulated, effector CD8⁺ T cells were activated at the secondary lymphoid organs, migrated, and subsequently released cytokines including interferon-γ and tumor necrosis factor-α, resulting in effective tumor regression.

CONCLUSIONS

Our anti-cancer strategy based on tumor-specific LP-iDOPE accumulation and low-intensity NIR-LED light irradiation to the tumor regions, i.e., photodynamic reaction, represents a promising approach to noninvasive cancer therapy.