Anti - Tumor Effect Of Porphyrin Sodium - Mediated Photodynamic Therapy On Mouse Breast Cancer

Background and purposeBreast cancer is the leading malignancy among women in the worldwide. However, effective therapies that reduce the high mortality rate and improve patient quality of life are still unavailable. In recent years, photodynamic therapy (PDT) has become a promising treatment strategy for cancer. It has many advantages, such as effective, safe, low side effects and cost, etc.Photosensitizers are critical components of PDT. One of the earliest clinical porphyrin-based photosensitizer is Photofrin(?) (PF), which has been approved by the FDA for use as a sensitizer in PDT of cancer and is the most widely used photosensitizer so far. PF has been approved for clinical use against early- and late-stage lung cancer, esophageal cancer, bladder cancer and malignant, nonmalignant early-stage cervical cancer in the worldwide. However, PF is known to be a mixture of dimers and oligomers of hematoporphyrin in which porphyrin units are linked by ether, ester and C-C bonds. Besides, it also requires a long clearance time (4-8 weeks) to avoid skin photosensitization. Patients are warned to avoid direct skin or eye exposure to sunlight or bright indoor light for at least 30 days post PF treatment. In addition, the cost of PF is very high, which also limit the application of it. In China, Hiporfin has been approved by the China’s State Food and Drug Administration (SFDA) in PDT of cancer treatments. But its anti-cancer effects were not as good as PF and it also has a long skin-sensitivity. So it has been discontinued at present.The disadvantages of using PF have stimulated efforts to develop more effective photosensitizers. Qicheng Fang and colleagues have performed numerous studies exploring the active portion of PF. They found the fraction that exhibited anti-cancer activity was porphyrin dimer salt connected by an ether bond. It was named Sinoporphyrin sodium, also referred to as DVDMS. DVDMS was granted intellectual property rights in China. In addition, DVDMS-based PDT was evaluated for skin phototoxicity and for growth inhibition in several xenograft tumors. DVDMS inhibits tumor growth to a greater extent than PF and has lower skin photctoxicity than Hiporfin, which was approved by the Chinese State Food and Drug Administration (SFDA) for use in PDT but whose production has been suspended by the manufacturer because of severe adverse effects. These early results suggested that DVDMS has great potential for use in clinical PDT.The function of DVDMS in PDT remains poorly understood, with only a patent and two publications being available on this aspect. Moreover, DVDMS-PDT has not been investigated in breast cancer models, and there are currently no reports on its role in treating metastasis. Here, we utilized the BALB/c-derived mouse mammary carcinoma cell line 4T1.These cancer cells share numerous characteristics with human mammary carcinoma, including immunogenicity, growth characteristics, and metastatic properties. We focused our investigation on the anti-tumor effects of DVDMS-PDT, examining proliferation and metastasis both in vitro and in vivo. These findings may have important implications for the treatment of cancer.Methods and ResultsPart 1 The study of DVDMS spectraThe multi-volume spectrophotometer system and fluorescence spectrophotometer were used to investigate the spectral characteristics of DVDMS. And the influences of pH and ionic strength on DVDMS spectra were also detected. The results showed that the absorption spectra of DVDMS had five distinct peaks at 362,516,548,579 and 631 nm, respectively, and the maximum peak (Soret peak) was about at 362 nm. The fluorescence spectra showed that DVDMS fluorescence emission was at 642 nm. Also, the pH and ionic strength of buffer solution caused changes of peak values and positions.Part 2 In vitro studies-the proliferation and metastasis inhibition effect of DVDMS-PDT was investigated in a highly metastatic 4T1 cell lineMTT assay and colony formation assay displayed that DVDMS could be effectively activated by light and the phototoxicity was much higher than PF under the same conditions. The phototoxic effect was mainly mediated by reactive oxygen species (ROS). Besides, wound healing assay and transwell assay indicated PDT combined with DVDMS effectively inhibited the migration of 4T1 cells. The morphological observation confirmed that the decrease of microvillus and collapse of F-action network might be involved in the effects seen on cell migration and invasion.Part 3 Detection of DVDMS biodistribution and concentrations in plasma, tumor and tissuesThe DVDMS biodistribution and concentrations in mice were detected by fluorospectrophotometry. The results showed that the concentration of DVDMS in the tumor was obviously higher than in the muscle and skin. It began raise for the first few hours and then reached peak at 12 h, was about 11 times and 6 times higher than in the muscle and skin, respectively. Between 12 h and 24 h, the DVDMS concentration in the tumor was still much higher than in the muscle and skin. At 48 h and 72 h, the concentration of DVDMS decreased to a lower level. The concentration of DVDMS in major organs reached peak in the first 2 hours, then decreased rapidly in the next 22 h. At 24 h, the DVDMS concentration in these organs all decreased to 50% or lower to their corresponding peak. In 48 h and 72 h, the DVDMS concentration was relatively low, indicated that most of DVDMS excreted during this time. The results suggest that in order to have a therapeutic effect on tumors (high concentration in tumors) and to minimize side effects on healthy tissues (low concentration in surrounding healthy tissues), DVDMS should be treated with light irradiation 24 h post administration.Part 4 In vivo studies-the anti-tumor effect of DVDMS-PDT was studied4T1 tumor-bearing mice models were established to evaluate the PDT effects of DVDMS through mice survival, tumor volume, tumor weight and lung metastases. The results revealed that PDT with DVDMS markedly prolonged the survival of the tumor-bearing mice and inhibited tumor growth and lung metastasis, consistent with in vitro findings.ConclusionIn summary, we performed both in vitro and in vivo assessments of the photodynamic effects of DVDMS on 4T1 breast cancer. The results suggest that DVDMS was more effective in inhibiting cancer growth and metastasis than PF, a conventional clinically used photosensitizer. Combined with the previously reported advantages, we propose that DVDMS is a promising sensitizer that warrants further development for PDT as well as other sensitizing drug-based therapies.