Circumvention of tumor cell escape following specific immunotherapy

Regulation of apoptosis-related genes by nitric oxide in cancer

Nitric oxide (NO) is a simple molecule with a complex and pleiotropic biological activity. NO or related species have been implicated in the regulation of many genes that participate in many diverse biological functions including programmed cell death or apoptosis. Apoptosis is a process that may potentially be disrupted in cancer cells conferring a survival advantage. In addition, malignant tumor cells can develop an intricate system of resistance to apoptotic stimuli. NO or related species have been shown to play a dual role in the regulation of apoptosis in malignant cells either promoting cell death or protecting cells from pro-apoptotic induction. However, the specific role of NO in the regulation of apoptosis/survival-related genes expression seems to tilt the balance toward the promotion of pro-apoptotic and the suppression of anti-apoptotic genes. Herein we have reviewed the most relevant aspects involving NO and/or reactive intermediates in the regulation of apoptosis-related genes--mainly--at the transcriptional level. We described the basic apoptotic molecules that potentially are affected by NO and how NO-mediated signaling gets transmitted to the transcriptional machinery that governs the expression of these genes. In addition, we discussed some of the fundamental functional consequences of the regulation of apoptosis-related genes by NO in cancer biology and its potential therapeutic implications.

Photodynamic therapy plus low-dose cyclophosphamide generates antitumor immunity in a mouse model

Photodynamic therapy (PDT) is a modality for the treatment of cancer involving excitation of nontoxic photosensitizers with harmless visible light-producing cytotoxic reactive oxygen species. PDT causes apoptosis and necrosis of tumor cells, destruction of the tumor blood supply, and activation of the immune system. The objective of this study was to compare in an animal model of metastatic cancer PDT alone and PDT combined with low-dose cyclophosphamide (CY) a treatment that has been proposed to deplete regulatory T cells (T-regs) and increase the immune response to some tumors. We used J774 tumors (a highly metastatic reticulum cell sarcoma line) and PDT with benzoporphyrin derivative monoacid ring A, verteporfin for injection (BPD; 1-mg/kg injected i.v. followed after 15 min by 150 J/cm(2) of 690-nm light). CY (50 or 150 mg/kg i.p.) was injected 48 h before light delivery. PDT alone led to tumor regressions and a survival advantage but no permanent cures were obtained. BPD-PDT in combination with low-dose CY (but not high-dose CY) led to 70% permanent cures. Low-dose CY alone gave no permanent cures but did provide a survival advantage and was shown to reduce CD4+FoxP3+ T-regs in lymph nodes, whereas high-dose CY reduced other lymphocyte classes as well. Cured animals were rechallenged with J774 cells, and the tumors were rejected in 71% of mice. Cured mice had tumor-specific T cells in spleens as determined by a (51)Cr release assay. We conclude that low-dose CY depletes T-regs and potentiates BPD-PDT, leading to tumor cures and memory immunity.