Inhibition of hyperprogressive cancer disease induced by immune-checkpoint blockade upon co-treatment with meta-tyrosine and p38 pathway inhibitor.

BACKGROUND: Although immune-checkpoint inhibitors (ICI) are overall promissory for cancer treatment, they entail, in some cases, an undesired side-effect called hyperprogressive-cancer disease (HPD) associated with acceleration of tumor growth and shortened survival. METHODS: To understand the mechanisms of HPD we assayed the ICI therapy on two murine tumors widely different regarding immunogenicity and, subsequently, on models of local recurrences and metastases of these tumors. To potentiate the immune response (IR), we combined ICI with meta-tyrosine-that counteracts immune-suppressive signals-and a selective inhibitor of p38 pathway that proved to counteract the phenomenon of tumor-immunostimulation. RESULTS: ICI were therapeutically effective against both tumor models (proportionally to their immunogenicity) but only when they faced incipient tumors. In contrast, ICI produced acceleration of large and residual tumors. The combined treatment strongly inhibited the growth of large tumors and it managed to cure 80% of mice with local recurrences and 60% of mice bearing residual metastases. CONCLUSIONS: Tumor enhancement was paradoxically correlated to a weak increase of the antitumor IR suggesting that a weak IR - different from a strong tumor-inhibitory one-may produce stimulation of tumor growth, mimicking the HPD observed in some clinical settings.

Improvement of Antitumor Therapies Based on Vaccines and Immune-Checkpoint Inhibitors by Counteracting Tumor-Immunostimulation.

Immune-checkpoint inhibitors and antitumor vaccines may produce both tumor-inhibitory and tumor-stimulatory effects on growing tumors depending on the stage of tumor growth at which treatment is initiated. These paradoxical results are not necessarily incompatible with current tumor immunology but they might better be explained assuming the involvement of the phenomenon of tumor immunostimulation. This phenomenon was originally postulated on the basis that the immune response (IR) evoked in Winn tests by strong chemical murine tumors was not linear but biphasic, with strong IR producing inhibition and weak IR inducing stimulation of tumor growth. Herein, we extended those former observations to weak spontaneous murine tumors growing in pre-immunized, immune-competent and immune-depressed mice. Furthermore, we demonstrated that the interaction of specifical T cells and target tumor cells at low stimulatory ratios enhanced the production of chemokines aimed to recruit macrophages at the tumor site, which, upon activation of toll-like receptor 4 and p38 signaling pathways, would recruit and activate more macrophages and other inflammatory cells which would produce growth-stimulating signals leading to an accelerated tumor growth. On this basis, the paradoxical effects achieved by immunological therapies on growing tumors could be explained depending upon where the therapy-induced IR stands on the biphasic IR curve at each stage of tumor growth. At stages where tumor growth was enhanced (medium and large-sized tumors), counteraction of the tumor-immunostimulatory effect with anti-inflammatory strategies or, more efficiently, with selective inhibitors of p38 signaling pathways enabled the otherwise tumor-promoting immunological strategies to produce significant inhibition of tumor growth.

Game-changing restraint of Ros-damaged phenylalanine, upon tumor metastasis.

An abrupt increase in metastatic growth as a consequence of the removal of primary tumors suggests that the concomitant resistance (CR) phenomenon might occur in human cancer. CR occurs in murine tumors and ROS-damaged phenylalanine, meta-tyrosine (m-Tyr), was proposed as the serum anti-tumor factor primarily responsible for CR. Herein, we demonstrate for the first time that CR happens in different experimental human solid tumors (prostate, lung anaplastic, and nasopharyngeal carcinoma). Moreover, m-Tyr was detected in the serum of mice bearing prostate cancer (PCa) xenografts. Primary tumor growth was inhibited in animals injected with m-Tyr. Further, the CR phenomenon was reversed when secondary implants were injected into mice with phenylalanine (Phe), a protective amino acid highly present in primary tumors. PCa cells exposed to m-Tyr in vitro showed reduced cell viability, downregulated NFκB/STAT3/Notch axis, and induced autophagy; effects reversed by Phe. Strikingly, m-Tyr administration also impaired both, spontaneous metastasis derived from murine mammary carcinomas (4T1, C7HI, and LMM3) and PCa experimental metastases. Altogether, our findings propose m-Tyr delivery as a novel approach to boost the therapeutic efficacy of the current treatment for metastasis preventing the escape from tumor dormancy.

Immature myeloid Gr-1+ CD11b+ cells from lipopolysaccharide-immunosuppressed mice acquire inhibitory activity in the bone marrow and migrate to lymph nodes to exert their suppressive function.

Secondary infections due to post-sepsis immunosuppression are a major cause of death in patients with sepsis. Repetitive inoculation of increasing doses of lipopolysaccharide (LPS) into mice mimics the immunosuppression associated with sepsis. Myeloid-derived suppressor cells (MDSCs, Gr-1(+) CD11b(+)) are considered a major component of the immunosuppressive network, interfering with T-cell responses in many pathological conditions. We used LPS-immunosuppressed (IS) mice to address whether MDSCs acquired their suppressive ability in the bone marrow (BM) and whether they could migrate to lymph nodes (LNs) to exert their suppressive function. Our results showed that Gr-1(+) CD11b(+) cells of IS mice already had the potential to inhibit T-cell proliferation in the BM. Moreover, soluble factors present in the BM from IS mice were responsible for inducing this inhibitory ability in control BM cells. In addition, migration of Gr-1(+) CD11b(+) to LNs in vivo was maximal when cells obtained from the BM of IS mice were inoculated into an IS context. In this regard, we found chemoattractant activity in cell-free LN extracts (LNEs) from IS mice and an increased expression of the LN-homing chemokine receptor C-C chemokine receptor type 7 (CCR7) in IS BM Gr-1(+) CD11b(+) cells. These results indicate that Gr-1(+) CD11b(+) cells found in BM from IS mice acquire their suppressive activity in the same niche where they are generated, and migrate to LNs to exert their inhibitory role. A better understanding of MDSC generation and/or regulation of factors able to induce their inhibitory function may provide new and more effective tools for the treatment of sepsis-associated immunosuppression.

Meta-tyrosine. A powerful anti-metastatic factor with undetectable toxic-side effects.

Concomitant tumor resistance (CR) is a phenomenon in which a tumor-bearing host is resistant to the growth of secondary tumor implants and metastasis. While former studies have indicated that T-cell dependent processes mediate CR in hosts bearing immunogenic small tumors, the most universal manifestation of CR induced by immunogenic and non-immunogenic large tumors had been associated with an antitumor serum factor that remained an enigma for many years. In a recent paper, we identified that elusive factor(s) as an equi-molar mixture of meta-tyrosine and ortho-tyrosine, two isomers of tyrosine that are not present in normal proteins and that proved to be responsible for 90% and 10%, respectively, of the total serum anti-tumor activity. In this work, we have extended our previous findings demonstrating that a periodic intravenous administration of meta-tyrosine induced a dramatic reduction of lung and hepatic metastases generated in mice bearing two different metastatic murine tumors and decreased the rate of death from 100% up to 25% in tumor-excised mice that already exhibited established metastases at the time of surgery. These anti-metastatic effects were achieved even at very low concentrations and without displaying any detectable toxic-side effects, suggesting that the use of meta-tyrosine may help to develop new and less harmful means of managing malignant diseases, especially those aimed to control the growth of metastases that is the most serious problem in cancer pathology.

Meta-tyrosine: A powerful anti-metastatic factor with undetectable toxic-side effects

Concomitant tumor resistance (CR) is a phenomenon in which a tumor-bearing host is resistant to the growth of secondary tumor implants and metastasis. While former studies have indicated that T-cell dependent processes mediate CR in hosts bearing immunogenic small tumors, the most universal manifestation of CR induced by immunogenic and non-immunogenic large tumors had been associated with an antitumor serum factor that remained an enigma for many years. In a recent paper, we identified that elusive factor(s) as an equi-molar mixture of meta-tyrosine and ortho-tyrosine, two isomers of tyrosine that are not present in normal proteins and that proved to be responsible for 90% and 10%, respectively, of the total serum anti-tumor activity. In this work, we have extended our previous findings demonstrating that a periodic intravenous administration of meta-tyrosine induced a dramatic reduction of lung and hepatic metastases generated in mice bearing two different metastatic murine tumors and decreased the rate of death from 100% up to 25% in tumor-excised mice that already exhibited established metastases at the time of surgery. These anti-metastatic effects were achieved even at very low concentrations and without displaying any detectable toxic-side effects, suggesting that the use of meta-tyrosine may help to develop new and less harmful means of managing malignant diseases, especially those aimed to control the growth of metastases that is the most serious problem in cancer pathology.

La resistencia concomitante antitumoral (RC) es el fenómeno según el cual un individuo portador de tumor inhibe el crecimiento de implantes tumorales secundarios y metástasis. Si bien desde hace tiempo se sabe que la RC inducida por tumores inmunogénicos de pequeño tamaño es generada por mecanismos inmunológicos dependientes de células T, por otro lado, la manifestación más universal de la RC, generada tanto por tumores inmunogénicos como no-inmunogénicos de gran tamaño, había sido asociada con un (unos) factor sérico antitumoral cuya naturaleza permaneció elusiva por años. En un trabajo reciente, nuestro grupo de trabajo identificó este factor como la mezcla equi-molar de meta-tirosina y orto-tirosina, dos isómeros de tirosina que no están presentes en proteínas normales y que demostraron ser responsables del 90% y 10%, respectivamente, de la actividad antitumoral total del suero. En este trabajo, continuamos nuestras investigaciones demostrando que la administración periódica de meta-tirosina reducía drásticamente el número de metástasis pulmonares y hepáticas en ratones portadores de dos tumores murinos altamente metastásicos y disminuía dramáticamente la mortandad (de 100% a 25%) de ratones con metástasis ya establecidas al momento de la extirpación quirúrgica del tumor. Estos efectos anti-metastásicos se lograron aun con muy bajas concentraciones de meta-tirosina y sin efectos tóxicos perceptibles, lo que sugiere que su uso puede ayudar a diseñar nuevas y menos nocivas estrategias para el tratamiento del cáncer, especialmente aquellas destinadas a controlar el crecimiento metastásico, que es el problema más grave en la enfermedad oncológica.

Meta-tyrosine: A powerful anti-metastatic factor with undetectable toxic-side effects

Concomitant tumor resistance (CR) is a phenomenon in which a tumor-bearing host is resistant to the growth of secondary tumor implants and metastasis. While former studies have indicated that T-cell dependent processes mediate CR in hosts bearing immunogenic small tumors, the most universal manifestation of CR induced by immunogenic and non-immunogenic large tumors had been associated with an antitumor serum factor that remained an enigma for many years. In a recent paper, we identified that elusive factor(s) as an equi-molar mixture of meta-tyrosine and ortho-tyrosine, two isomers of tyrosine that are not present in normal proteins and that proved to be responsible for 90% and 10%, respectively, of the total serum anti-tumor activity. In this work, we have extended our previous findings demonstrating that a periodic intravenous administration of meta-tyrosine induced a dramatic reduction of lung and hepatic metastases generated in mice bearing two different metastatic murine tumors and decreased the rate of death from 100% up to 25% in tumor-excised mice that already exhibited established metastases at the time of surgery. These anti-metastatic effects were achieved even at very low concentrations and without displaying any detectable toxic-side effects, suggesting that the use of meta-tyrosine may help to develop new and less harmful means of managing malignant diseases, especially those aimed to control the growth of metastases that is the most serious problem in cancer pathology.(AU)

La resistencia concomitante antitumoral (RC) es el fenómeno según el cual un individuo portador de tumor inhibe el crecimiento de implantes tumorales secundarios y metástasis. Si bien desde hace tiempo se sabe que la RC inducida por tumores inmunogénicos de pequeño tamaño es generada por mecanismos inmunológicos dependientes de células T, por otro lado, la manifestación más universal de la RC, generada tanto por tumores inmunogénicos como no-inmunogénicos de gran tamaño, había sido asociada con un (unos) factor sérico antitumoral cuya naturaleza permaneció elusiva por años. En un trabajo reciente, nuestro grupo de trabajo identificó este factor como la mezcla equi-molar de meta-tirosina y orto-tirosina, dos isómeros de tirosina que no están presentes en proteínas normales y que demostraron ser responsables del 90% y 10%, respectivamente, de la actividad antitumoral total del suero. En este trabajo, continuamos nuestras investigaciones demostrando que la administración periódica de meta-tirosina reducía drásticamente el número de metástasis pulmonares y hepáticas en ratones portadores de dos tumores murinos altamente metastásicos y disminuía dramáticamente la mortandad (de 100% a 25%) de ratones con metástasis ya establecidas al momento de la extirpación quirúrgica del tumor. Estos efectos anti-metastásicos se lograron aun con muy bajas concentraciones de meta-tirosina y sin efectos tóxicos perceptibles, lo que sugiere que su uso puede ayudar a diseñar nuevas y menos nocivas estrategias para el tratamiento del cáncer, especialmente aquellas destinadas a controlar el crecimiento metastásico, que es el problema más grave en la enfermedad oncológica.(AU)

all-trans-retinoic acid improves immunocompetence in a murine model of lipopolysaccharide-induced immunosuppression.

Secondary infections due to post-sepsis immunosuppression are a major cause of death in patients with sepsis. Strategies aimed at restoring immune functions offer a new perspective in the treatment of sepsis. In the present study, we used LPS (lipopolysaccharide)-immunosuppressed mice to analyse the effects of ATRA (all-trans retinoic acid) on different immune parameters. The IS (immunocompromised) group had decreased lymphocyte and increased MDSC (myeloid-derived suppressor cell) counts in lymph nodes. They also had an impaired in vitro T-cell proliferation, mediated by MDSCs. ATRA administration restored T-cell proliferation, which was associated with a decreased number of live MDSCs. The IS group treated with ATRA had an increased number of CD4+ and CD8+ T-cells. ATRA partially improved the primary humoral immune response, even when immunosuppression was established first and ATRA was administered subsequently. Our results demonstrate that ATRA restores immunocompetence by modulating the number of leucocytes and the survival of MDSCs, and thus represents an additional potential strategy in the treatment of the immunosuppressive state of sepsis.

Concomitant tumor resistance.

Concomitant tumor resistance (CR) is a phenomenon in which a tumor-bearing host is resistant to the growth of secondary tumor implants. This phenomenon has been described in human and animal systems and it can be generated by both immunogenic and non-immunogenic tumors. The relevance of CR to the mechanisms of metastases control has been highlighted by numerous observations showing that the removal of human and murine tumors may be followed by an abrupt increase in metastatic growth, suggesting that a primary tumor may exert a controlling action on its metastases which could be considered as secondary tumor implants developed spontaneously during the primary tumor growth. A more profound understanding of the different mechanisms claimed to be associated with the phenomenon of CR could contribute to develop new and more harmless means to manage malignant diseases, especially by limiting the development of metastases that arise after resection of primary tumors or after other stressors that may promote the escape of metastases from dormancy.

Concomitant tumor resistance: the role of tyrosine isomers in the mechanisms of metastases control.

Concomitant tumor resistance (CR) is a phenomenon in which a tumor-bearing host is resistant to the growth of secondary tumor implants and metastasis. Although previous studies indicated that T-cell-dependent processes mediate CR in hosts bearing immunogenic small tumors, manifestations of CR induced by immunogenic and nonimmunogenic large tumors have been associated with an elusive serum factor. In a recently published study, we identified this factor as meta-tyrosine and ortho-tyrosine, 2 isomers of tyrosine that would not be present in normal proteins. In 3 different murine models of cancer that generate CR, both meta- and ortho-tyrosine inhibited tumor growth. Additionally, we showed that both isoforms of tyrosine blocked metastasis in a fourth model that does not generate CR but is sensitive to CR induced by other tumors. Mechanistic studies showed that the antitumor effects of the tyrosine isomers were mediated in part by early inhibition of the MAP/ERK pathway and inactivation of STAT3, potentially driving tumor cells into a state of dormancy in G(0)-phase. Other mechanisms, putatively involving the activation of an intra-S-phase checkpoint, would also inhibit tumor proliferation by accumulating cells in S-phase. By revealing a molecular basis for the classical phenomenon of CR, our findings may stimulate new generalized approaches to limit the development of metastases that arise after resection of primary tumors or after other stressors that may promote the escape of metastases from dormancy, an issue that is of pivotal importance to oncologists and their patients.

On the immunostimulatory hypothesis of cancer.

There is a rather generalized belief that the worst possible outcome for the application of immunological therapies against cancer is a null effect on tumor growth. However, a significant body of evidence summarized in the immunostimulatory hypothesis of cancer suggests that, upon certain circumstances, the growth of incipient and established tumors can be accelerated rather than inhibited by the immune response supposedly mounted to limit tumor growth. In order to provide more compelling evidence of this proposition, we have explored the growth behavior characteristics of twelve murine tumors -most of them of spontaneous origin- arisen in the colony of our laboratory, in putatively immunized and control mice. Using classical immunization procedures, 8 out of 12 tumors were actually stimulated in "immunized" mice while the remaining 4 were neither inhibited nor stimulated. Further, even these apparently non-antigenic tumors could reveal some antigenicity if more stringent than classical immunization procedures were used. This possibility was suggested by the results obtained with one of these four apparently non-antigenic tumors: the LB lymphoma. In effect, upon these stringent immunization pretreatments, LB was slightly inhibited or stimulated, depending on the titer of the immune reaction mounted against the tumor, with higher titers rendering inhibition and lower titers rendering tumor stimulation. All the above results are consistent with the immunostimulatory hypothesis that entails the important therapeutic implications -contrary to the orthodoxy- that, anti-tumor vaccines may run a real risk of doing harm if the vaccine-induced immunity is too weak to move the reaction into the inhibitory part of the immune response curve and that, a slight and prolonged immunodepression -rather than an immunostimulation- might interfere with the progression of some tumors and thus be an aid to cytotoxic therapies.

Tyrosine isomers mediate the classical phenomenon of concomitant tumor resistance.

Concomitant tumor resistance (CR) is a phenomenon originally described in 1906 in which a tumor-bearing host is resistant to the growth of secondary tumor implants and metastasis. Although recent studies have indicated that T-cell-dependent processes mediate CR in hosts bearing immunogenic small tumors, manifestations of CR induced by immunogenic and nonimmunogenic large tumors have been associated with an elusive serum factor. In this study, we identify this serum factor as tyrosine in its meta and ortho isoforms. In three different murine models of cancer that generate CR, both meta-tyrosine and ortho-tyrosine inhibited tumor growth. In addition, we showed that both isoforms of tyrosine blocked metastasis in a fourth model that does not generate CR but is sensitive to CR induced by other tumors. Mechanistic studies showed that the antitumor effects of the tyrosine isoforms were mediated, in part, by early inhibition of mitogen-activated protein/extracellular signal-regulated kinase pathway and inactivation of STAT3, potentially driving tumor cells into a state of dormancy. By revealing a molecular basis for the classical phenomenon of CR, our findings may stimulate new generalized approaches to limit the development of metastases that arise after resection of primary tumors, an issue of pivotal importance to oncologists and their patients.

Model of polymicrobial peritonitis that induces the proinflammatory and immunosuppressive phases of sepsis.

Severe sepsis is associated with early release of inflammatory mediators that contribute to the morbidity and mortality observed during the first stages of this syndrome. Although sepsis is a deadly, acute disease, high mortality rates have been observed in patients displaying evidence of sepsis-induced immune deactivation. Although the contribution of experimental models to the knowledge of pathophysiological and therapeutic aspects of human sepsis is undeniable, most of the current studies using animal models have focused on the acute, proinflammatory phase. We developed a murine model that reproduces the early acute phases but also the long-term consequences of human sepsis. We induced polymicrobial acute peritonitis (AP) by establishing a surgical connection between the cecum and the peritoneum, allowing the exit of intestinal bacteria. Using this model, we observed an acute phase with high mortality, leukopenia, increased interleukin-6 levels, bacteremia, and neutrophil activation. A peak of leukocytosis on day 9 or 10 revealed the persistence of the infection within the lung and liver, with inflammatory hepatic damage being shown by histological examination. Long-term (20 days) derangements in both innate and adaptive immune responses were found, as demonstrated by impaired systemic tumor necrosis factor alpha production in response to an inflammatory stimulus; a decreased primary humoral immune response and T cell proliferation, associated with an increased number of myeloid suppressor cells (Gr-1(+) CD11b(+)) in the spleen; and a low clearance capacity. This model provides a good approach to attempt novel therapeutic interventions directed to augmenting host immunity during late sepsis.

Biphasic effect of a primary tumor on the growth of secondary tumor implants.

BACKGROUND: The phenomenon of hormesis is characterized by a biphasic dose-response, exhibiting opposite effects in the low- and high-dose zones. In this study, we explored the possibility that the hormesis concept may describe the interactions between two tumors implanted in a single mouse, such that the resulting tumors are of different sizes. MATERIALS AND METHODS: We used two murine tumors of spontaneous origin and undetectable immunogenicity growing in BALB/c mice. A measure of cell proliferation was obtained by immunostaining for Ki-67 protein and by using the [(3)H] thymidine uptake assay. For serum fractionation, we utilized dialysis and chromatography on Sephadex G-15. RESULTS: The larger primary tumor induced inhibitory or stimulatory effects on the growth of the smaller secondary one, depending on the ratio between the mass of the larger tumor relative to that of the smaller one, with high ratios rendering inhibition and low ratios inducing stimulation of the secondary tumor. CONCLUSION: Since metastases can be considered as natural secondary tumor implants in a tumor-bearing host and that they constitute the main problem in cancer pathology, the use of the concept of hormesis to describe those biphasic effects might have significant clinical implications. In effect, if the tumor-bearing host were placed in the inhibitory window, tumor extirpation could enhance the growth of distant metastases and, reciprocally, if placed in the stimulatory window, tumor extirpation would result not only in a reduction or elimination of primary tumor load but also in a slower growth or inhibition of metastases.

[Unveiling antigens in a non-immunogenic spontaneous murine tumor using a dendritic cell based vaccine]. / Hallazgo de antígenos en un tumor murino espontáneo no inmunogénico mediante el uso de una vacuna basada en células dendríticas.

Up to date, most attempts to use immunotherapy to cause the regression of animal and human established tumors have not been successful. Former experiments have postulated that this failure could be attributed, at least in part, to a lack of immunogenicity of spontaneous tumors. In this paper, we have investigated whether this lack of immunogenicity can be attributed to the absence of tumor antigens or to the existence of tolerogenic mechanisms preventing such antigens from initiating an antitumor immune response. We have used two murine tumors a non-immunogenic spontaneous lymphoma (LB) and a strongly immunogenic methylcholanthrene-induced fibrosarcoma (MC-C) together with a vaccination strategy based on the inoculation of dendritic cells (DC) loaded with a tumor lysate. When DC were pulsed with LB lysate (DC+LB), no maturation of DC was achieved in vitro and no protection against LB implants after DC+LB inoculation was observed in vivo. On the other hand, when DC were pulsed with MC-C lysate (DC+MC-C), maturation of DC was observed along with a strong protection against MC-C implants after DC+MC-C inoculaton. Finally, when DC were pulsed with both LB and MC-C lysates (DC+LB+MC-C), maturation of DC and protection against LB implants were achieved. Since no immune cross reaction between MC-C and LB was ever observed, the most likely interpretation is that LB bears specific tumor antigens but lacks other signals to achieve DC maturation. These signals would be provided by MC-C which would enable DC to mature and to initiate an effective anti-LB immune response.

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

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.

Therapeutic anti-tumor vaccines: from tumor inhibition to enhancement.

Numerous immunization trials have proved successful in preventing the growth of experimental animal tumors and human hepatocarcinomas induced by hepatitis B virus. These results have prompted researchers and physicians to use vaccines in a therapeutic mode but the results have, in general, been disappointing even when strongly immunogenic murine tumors were concerned. Data presented herein suggest that immunotherapy induced by a single dose of a dendritic cell-based vaccine against a murine established tumor or against residual tumor cells after debulking the primary tumor, can render not only inhibitory or null but also stimulatory effects on tumor growth. These different effects might be dependent on where the system is located in the immune response curve that relates the quantity of the immune response to the quantity of target tumor cells. We suggest that high ratios render tumor inhibition, medium and very low ratios render null effects and low ratios-between medium and very low ones-render tumor stimulation. Since the magnitude of these ratios would depend on the antigenic profile of the tumor, the immunogenic strength of the vaccine used and the immunological state of the host, studies aimed to determine the magnitude of these variables in each particular case, seem to be necessary as a pre-condition to design rational immunotherapeutic approaches to cancer. In contrast, if these studies are neglected, the worst thing that an immunotherapist could face is not merely a null effect but enhancement of tumor growth.

[Systemic inflammation and experimental cancer in a murine model]. / Cáncer experimental e inflamación sistémica en un modelo murino.

The link between cancer and inflammation in an organ or tissue has firmly been established on the basis that cancer tends to occur at sites of chronic inflammation and that local inflammatory processes can accelerate the growth of preexisting tumors in both animals and human beings. In contrast, the relationship between cancer and systemic inflammation has been less studied. In this work, we demonstrated that the growth of the murine fibrosarcoma MC-C, was accompanied by manifestations of systemic inflammation, as demonstrated by an increase in both the number of circulating polymorphonuclear neutrophils (PMN) and the serum concentration of the proinflammatory cytokines interleukin-1beta (IL-1beta), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) and the acute phase proteins C reactive (CRP) and serum A amyloid (SAA). Two temporally separate peaks of systemic inflammation were detected during tumor development. The first was displayed during the first week after tumor inoculation. The second peak began around day 14 and its intensity was proportional to tumor size. In mice bearing a large MC-C tumor, a high number of circulating PMN and myeloid precursors were evident. Most of these cells exhibited activation evidenced by an increased reactive oxygen species generation and high expression of the Gr1+/Mac1+ markers. Inoculation of thioglycolate -which generates a transient systemic inflammation-accelerated the growth of MC-C tumor and reciprocally, inhibition of such systemic inflammation by using indomethacin, prevented that enhancing effect. This suggests that the systemic inflammation that the tumor generates on its own, could be part of its growth strategy.