Reversión del eclipse inmunológico y vacunación terapéutica contra el cáncer en un modelo experimental / Reversion of the immunological eclipse and therapeutic vaccination against cancer in an experimental model

Aunque existen vacunas para prevenir la aparición de tumores en animales de experimentación, la mayoría de los intentos por aplicar aquellas vacunas con fines terapéuticos contra tumores establecidos no han sido exitosos. Para comprender la naturaleza de esta refractariedad, estudiamos un tumor de ratón fuertemente inmunogénico inducido por el carcinógeno químico metilcolantreno. En nuestro modelo, el inicio de esta refractariedad coincidió con el comienzo de un estado de inmunosupresión conocido como "eclipse inmunológico" caracterizado por una pérdida o bloqueo de la respuesta inmune antitumoral después que el tumor ha superado cierto tamaño crítico. Este eclipse inmunológico fue acompañado por un proceso de inflamación sistémica en el organismo. El tratamiento de los ratones portadores de tumor con una única dosis del corticoide sintético dexametasona (DX) redujo los parámetros de inflamación sistémica e indujo la reversión del eclipse. Esta reversión no fue por sí misma curativa pero permitió que un tratamiento inmunológico basado en células dendríticas estimuladas con antígenos tumorales, que por sí solo era absolutamente ineficaz, pudiera ejercer un significativo efecto inhibidor sobre un tumor en crecimiento. El esquema de dos pasos que comprende, primero, un tratamiento antiinflamatorio para revertir el eclipse y segundo, una estrategia de vacunación basada en células dendríticas destinada a estimular la respuesta inmune antitumoral, podría servir, eventualmente, como un modelo de inmunoterapia contra tumores en animales y seres humanos.

Although animals can be prophylactically immunized against the growth of tumor implants, most of the attempts to use immunotherapy to cause the regression of animal and human tumors once they become established have been unsuccessful. To understand the nature of this refractoriness we have studied a methylcholanthrene-induced and strongly immunogenic murine fibrosarcoma. In our model, the onset of this refractoriness was associated with the beginning of an immunosuppressive state known as "immunological eclipse" characterized by a loss of the antitumor immune response when tumor grows beyond a critical size. This immunological eclipse was accompanied by the emergence of a systemic inflammatory condition. Treatment of tumor-bearing mice with a single dose of a synthetic corticosteroid, dexamethasone (DX), reduced significantly all parameters of systemic inflammation and simultaneously reversed the immunological eclipse. The reversion of the eclipse upon DX treatment was not curative itself, but allowed an immunological therapy based in dendritic cells pulsed with tumor antigens, which was itself absolutely ineffective, to exert a significant inhibitory effect against an established growing tumor. The two-step schedule using an anti-inflammatory treatment to reverse the immunological eclipse plus a dendritic cell-based vaccination strategy aimed to stimulate the anti-tumor immune response, could serve eventually as a model of immunotherapy against animal and human tumors.

Role of bio-metal Fe(III) in anticancer effect of dacarbazine.

Physicochemical, Microbial and Pharmacological studies on Fe(III)-Dacarbazine complex have been done in solid and aqueous phase. On the basis of elemental analysis, polarographic studies, amperometric titrations and IR spectral studies the probable formula for the complex has been worked out to be 1:1, Fe(III)-Dacarbazine. The metal ligand interaction has been studied using polarographic method at 25 +/- 1 degrees C and at ionic strength of mu = 1.0 (KCl). Microbial studies on the complex was done against various pathogenic bacteria viz. Pseudomonas mangiferae, Staphylococcus aureus, Salmonella typhi and Vibrio cholarae and fungi i.e. Trichothecium and Chrysosporium sp. using Raper's method. Mouse sarcoma cell line 180 and Balb/C mice were used for the anticancer screening of solid complex in vitro and in vivo respectively. The observed polarographic data, on lingane treatment revealed the formation of single (1:1) (M:L) complex with Fe(III) and dacarbazine ligands. The results of amperometric titrations of Fe(III) with dacarbazine in IM KCl supporting electrolyte pH 7.0 +/- 0.1 supported the above findings the IR data speaks of the complex formation between the metal and the dacarbazine ligand through the two nitrogen one each of primary amide and trizo groups. The results of microbial and pharmacological studies with the M:Drug complex revealed that the anticancer activity of the drug metal complex is nearly doubled as compared to the pure drug. As such Fe(III) dacarbazine complex may be recommended to the therapeutic experts for its possible use as more potent anticancer drug.

Multimodality treatment using AK-2123, hydralazine, radiation & hyperthermia on a transplantable mouse tumour.

The in vivo response of a transplantable mouse tumour, Sarcoma 180 to AK-2123 (AK), local irradiation (RT) and local hyperthermia, as influenced by a vasoactive drug, hydralazine (HDZ), was assessed on the basis of tumour cure (complete response CR), volume doubling time (VDT), regrowth delay (RD) and animal survival up to 120 days. A single ip injection of 200 mg/kg b.wt. AK produced more than 15 per cent CR. Combination of any two agents resulted in a better response than the single agent treatments. AK in combination with 43 degrees C, 30 min (HT) was more effective than HT combination with 10 Gy. The presence of 5 mg/kg HDZ, injected immediately after 5 Gy, in combination with AK increased the therapeutic effect over that produced by AK+10Gy. Combination of all the three agents (AK+10Gy+HT) produced 100 per cent CR and prolonged disease free animal survival. A similar response could be obtained by the presence of HDZ with a lower radiation dose of 5 Gy in combination with AK and HT (AK+5Gy+HDZ+HT). This multimodality treatment offers the possibility of further reduction in the doses of individual agents, and in the possible side effects on normal tissues without compromising the tumour cure effect.

Chlorophyll derivatives: a new photosensitizer for photodynamic therapy of cancer in mice

The in vivo photosensitizing efficacy of chlorophyll derivatives(CpD), which had been developed as a new photosensitizer, was compared with that of hematoporphyrin derivatives (HpD). A murine tumor model implanted subcutaneously with S-180 cells on the abdomen was used. The CpD or HpD was administered by intratumoral injection, and light of appropriate wavelength was irradiated on the tumor areas for 10 minutes at 1h and 24h or 24h and 48h after the injection of photosensitizer. When CpD was injected, the early irradiation group (1h and 24h) showed a 100% tumor cure rate; however, the late irradiation group (24h and 48h) showed a 60% tumor cure rate (p less than 0.01). This showed that the early irradiation with light after injection of CpD was an important factor for obtaining better results. With HpD, there was no difference in tumor cure rate between early (1h and 24h, 80%) and late irradiation (24h and 48h, 80%) groups. Thus, in early irradiation groups, the tumor cure rate using CpD (100%) was superior to that of HpD (80%) (p less than 0.05). However, in late irradiation groups, the tumor cure rate using CpD (60%) was inferior to that of HpD (80%), but this difference was not statistically significant (p greater than 0.1). Pathologic sections of these tumors were made before treatment and 48h and 3 weeks after treatment. These showed geographic necrosis at 48h after treatment and no viable tumor tissue at 3 weeks after treatment. Our results showed that CpD was as effective as HpD as a photosensitizer for in vivo photodynamic therapy.

Chlorophyll derivatives: a new photosensitizer for photodynamic therapy of cancer in mice

The in vivo photosensitizing efficacy of chlorophyll derivatives(CpD), which had been developed as a new photosensitizer, was compared with that of hematoporphyrin derivatives (HpD). A murine tumor model implanted subcutaneously with S-180 cells on the abdomen was used. The CpD or HpD was administered by intratumoral injection, and light of appropriate wavelength was irradiated on the tumor areas for 10 minutes at 1h and 24h or 24h and 48h after the injection of photosensitizer. When CpD was injected, the early irradiation group (1h and 24h) showed a 100% tumor cure rate; however, the late irradiation group (24h and 48h) showed a 60% tumor cure rate (p less than 0.01). This showed that the early irradiation with light after injection of CpD was an important factor for obtaining better results. With HpD, there was no difference in tumor cure rate between early (1h and 24h, 80%) and late irradiation (24h and 48h, 80%) groups. Thus, in early irradiation groups, the tumor cure rate using CpD (100%) was superior to that of HpD (80%) (p less than 0.05). However, in late irradiation groups, the tumor cure rate using CpD (60%) was inferior to that of HpD (80%), but this difference was not statistically significant (p greater than 0.1). Pathologic sections of these tumors were made before treatment and 48h and 3 weeks after treatment. These showed geographic necrosis at 48h after treatment and no viable tumor tissue at 3 weeks after treatment. Our results showed that CpD was as effective as HpD as a photosensitizer for in vivo photodynamic therapy.