Anti-inflammatory pretreatment enables an efficient dendritic cell-based immunotherapy against established tumors

Abstract

Although animals can be immunized against the growth of some tumor implants, most of the attempts to use immunotherapy to cause the regression of animal and human tumors once they have become established have been disappointing even when strongly immunogenic tumors were used as target. In this paper, we demonstrate that the failure to achieve an efficient immunological treatment against an established strongly immunogenic murine fibrosarcoma was paralleled with the emergence of a state of immunological unresponsiveness (immunological eclipse) against tumor antigens observed when the tumor surpassed the critical size of 500 mm(3). In turn, the onset of the immunological eclipse was coincidental with the onset of a systemic inflammatory condition characterized by a high number of circulating and splenic polymorphonucleated neutrophils (PMN) displaying activation and Gr1(+)Mac1(+) phenotype and an increasing serum concentration of the pro-inflammatory cytokines TNF-alpha, IL-1beta and IL-6 cytokines and C-reactive protein (CRP) and serum A amyloid (SAA) phase acute proteins. Treatment of tumor-bearing mice with a single low dose (0.75 mg/kg) of the synthetic corticoid dexamethasone (DX) significantly reduced all the systemic inflammatory parameters and simultaneously reversed the immunological eclipse, as evidenced by the restoration of specific T-cell-dependent concomitant immunity, ability of spleen cells to transfer anti-tumor activity and recovery of T-cell signal transduction molecules. Two other anti-inflammatory treatments by using indomethacin or dimeric TNF-alpha receptor, also partially reversed the immunological eclipse although the effect was not as striking as that observed with DX. The reversion of the immunological eclipse was not enough on its own to inhibit the primary growing tumor. However, when we used the two-step strategy of inoculating DX to reverse the eclipse and then dendritic cells loaded with tumor antigens (DC) as an immunization booster, a significant inhibition of the growth of both established tumors and remnant tumor cells after excision of large established tumors was observed, despite the fact that the vaccination alone (DC) had no effect or even enhanced tumor growth in certain circumstances. The two-step strategy of tumor immunotherapy that we present is based on the rationale that it is necessary to eliminate or ameliorate the immunological eclipse as a precondition to allow an otherwise ineffective anti-tumor immunological therapy to have a chance to be successful.

Concomitant Tumor Resistance: The Role of Tyrosine Isomers in the Mechanisms of Metastases Control

“…However, it was recently suggested that oxidized amino acids, such as m-and o-Tyr, may also be generated from free amino acids that subsequently could be incorporated into proteins during synthesis (48,49). We previously observed that the serum antitumor activity attributed to m-and o-Tyr was strongly inhibited by agents that reduced the number of myeloid-derived suppressor cells (MDSC) and oxidative damage, and that in tumor-bearing mice (including the LB tumor model used in this work) and some cancer patients, MDSCs that produced large amounts of reactive oxygen species accumulated progressively in circulation (46,(50)(51)(52)(53). On the basis of these results, we suggested that free m-and o-Tyr present in the serum from tumor-bearing mice will be produced, at least in part, when circulating molecules of Phe are oxidized by hydroxyl radicals released by MDSC.…”

Tyrosine Isomers Mediate the Classical Phenomenon of Concomitant Tumor Resistance

“…The following tumors were also used: MC-C (fibrosarcoma), CEI (epidermoid carcinoma), and the highly metastatic C7HI (mammary adenocarcinoma), that were described previously (9,22,23).…”

“…Western blotting was carried out with standard techniques as described (23) and analyzed by ImageQuant software. The following antibodies were used: anti-p-Erk 1/2, anti-ERK 1/2, anti-p-STAT3, anti-STAT3 (Santa Cruz), and anti-b-actin (Cell Signaling Technology).…”

B cells inhibit the antitumor immunity against an established murine fibrosarcoma

“…Methylcolanthrene-induced murine fibrosarcoma (MCC) is a highly immunogenic tumor that elicits an early specific antitumor immune reaction, which is not strong enough to impede tumor growth (18)(19)(20)(21). The antitumor response declines at a certain tumor volume (~500 mm 3 ) and disappears comprising a state of tolerance (18)(19)(20)(21). Immunological characteristics of MCC and its rapid growth in vivo make it a suitable model to study mechanisms underlying tumor immunity and tumor-induced immunosuppression.…”

“…Evidence that accounts for the role of B cells in tumor-induced immunosuppression includes the existence of human B cells with a regulatory phenotype in solid tumors (11), the B cell-mediated induction of Tregs expansion (12)(13)(14) and the increase of tumor growth (12,(15)(16)(17). Methylcolanthrene-induced murine fibrosarcoma (MCC) is a highly immunogenic tumor that elicits an early specific antitumor immune reaction, which is not strong enough to impede tumor growth (18)(19)(20)(21). The antitumor response declines at a certain tumor volume (~500 mm 3 ) and disappears comprising a state of tolerance (18)(19)(20)(21).…”