Induction of an antitumour adaptive immune response elicited by tumour cells expressing de novo B7-1 mainly depends on the anatomical site of their delivery: the dose applied regulates the expansion of the response

Autologous cellular vaccine overcomes cancer immunoediting in a mouse model of myeloma

In the Sp6 mouse plasmacytoma model, a whole-cell vaccination with Sp6 cells expressing de novo B7-1 (Sp6/B7) induced anatomically localized and cytotoxic T cell (CTL)-mediated protection against wild-type (WT) Sp6. Both WT Sp6 and Sp6/B7 showed down-regulated expression of MHC H-2 L(d). Increase of H-2 L(d) expression by cDNA transfection (Sp6/B7/L(d)) raised tumour immune protection and shifted most CTL responses towards H-2 L(d)-restricted antigenic epitopes. The tumour-protective responses were not specific for the H-2 L(d)-restricted immunodominant AH1 epitope of the gp70 common mouse tumour antigen, although WT Sp6 and transfectants were able to present it to specific T cells in vitro. Gp70 transcripts, absent in secondary lymphoid organs of naive mice, were detected in immunized mice as well as in splenocytes from naive mice incubated in vitro with supernatants of CTL-lysed Sp6 cell cultures, containing damage-associated molecular patterns (DAMPs). It has been shown that Toll-like receptor triggering induces gp70 expression. Damage-associated molecular patterns are released by CTL-mediated killing of Sp6/B7-Sp6/B7/L(d) cells migrated to draining lymph nodes during immunization and may activate gp70 expression and presentation in most resident antigen-presenting cells. The same could also apply for Mus musculus endogenous ecotropic murine leukaemia virus 1 particles present in Sp6-cytosol, discharged by dying cells and superinfecting antigen-presenting cells. The outcome of such a massive gp70 cross-presentation would probably be tolerogenic for the high-affinity AH1-gp70-specific CTL clones. In this scenario, autologous whole-tumour-cell vaccines rescue tumour-specific immunoprotection by amplification of subdominant tumour antigen responses when those against the immune dominant antigens are lost.

Efficacy assessment of interferon-alpha-engineered mesenchymal stromal cells in a mouse plasmacytoma model

Bone marrow mesenchymal stromal cells (BM-MSCs) may survive and proliferate in the presence of cycling neoplastic cells. Exogenously administered MSCs are actively incorporated in the tumor as stromal fibroblasts, thus competing with the local mesenchymal cell precursors. For this reason, MSCs have been suggested as a suitable carrier for gene therapy strategies, as they can be genetically engineered with genes encoding for biologically active molecules that can inhibit tumor cell proliferation and enhance the antitumor immune response. We used BM-MSCs engineered with the murine interferon-alpha (IFN-α) gene (BM-MSCs/IFN-α) to assess in a mouse plasmacytoma model the efficacy of this approach toward neoplastic plasma cells. We found that IFN-α can be efficiently produced and delivered inside the tumor microenvironment. Subcutaneous multiple administration of BM-MSCs/IFN-α significantly hampered the tumor growth in vivo and prolonged the overall survival of mice. The antitumor effect was associated with enhanced apoptosis of tumor cells, reduction in microvessel density, and ischemic necrosis. By contrast, intravenous administration of BM-MSCs/IFN-α did not significantly modify the survival of mice, mainly as a consequence of an excessive entrapment of injected cells in the pulmonary vessels. In conclusion, BM-MSCs/IFN-α are effective in inhibiting neoplastic plasma cell growth; however, systemic administration of engineered MSCs needs to be improved to make this approach potentially suitable for the treatment of multiple myeloma.

IFN-gamma-mediated upmodulation of MHC class I expression activates tumor-specific immune response in a mouse model of prostate cancer

De novo expression of B7-1 impaired tumorigenicity of TRAMP-C2 mouse prostate adenocarcinoma (TRAMP-C2/B7), but it did not elicit a protective response against TRAMP-C2 parental tumor, unless after in vitro treatment with IFN-gamma. TRAMP-C2 cells secrete TGF-beta and show low MHC-I expression. Treatment with IFN-gamma increased MHC-I expression by induction of some APM components and antagonizing the immunosuppressant activity of TGF-beta. Thus, immunization with TRAMP-C2/B7 conferred protection against TRAMP-C2-derived tumors in function of the IFN-gamma-mediated fine-tuned modulation of either APM expression or TGF-beta signaling. To explore possible clinical translation, we delivered IFN-gamma to TRAMP-C2 tumor site by means of genetically engineered MSCs secreting IFN-gamma.

Estimating the Growth Kinetics of Experimental Tumors From as Few as Two Determinations of Tumor Size: Implications for Clinical Oncology

Clinical information on tumor growth is often limited to a few determinations of the size of the tumor burden taken at variable time. As a consequence, fitting of growth equations to clinical data is hampered by the small number of available data. On the other hand, characterising the tumor growth kinetics in terms of clinically relevant parameters, such as the doubling time of the tumors, is increasingly required to optimize and personalise treatments. A computational method is presented which can estimate the growth kinetics of tumors from as few as two determinations of its size taken at two successive time points, provided the size at which tumor growth saturates is known. The method is studied by using experimental data obtained in vitro with multicell tumor spheroids and in vivo with tumors grown in mice, and its outputs are compared to those obtained by fitting of experimental data with the Gompertz growth equation. Under certain assumptions and limitations the method provides comparable estimates of the doubling time of tumors with respect to the classical nonlinear fitting approach. The method is then tested against simulated tumor growth trajectories spanning the range of tumor sizes observed in the clinics. The simulations show that a relative classification of tumors on the basis of their growth kinetics can be obtained even if the size at which tumor growth saturates is not known. This result opens the possibility to classify patients bearing fast or slow growing tumors and, hence, to adapt therapeutic regimens under a more rationale basis.

Anti-tumour potential of a gallic acid-containing phenolic fraction from Oenothera biennis

A phenolic fraction purified form defatted seeds of Oenothera biennis promoted selective apoptosis of human and mouse bone marrow-derived cell lines following first-order kinetics through a caspase-dependent pathway. In non-leukemia tumour cell lines, such as human colon carcinoma CaCo(2) cells and mouse fibrosarcoma WEHI164 cells, this fraction inhibited (3)H-thymidine incorporation but not cell death or cell cycle arrest. Human peripheral blood mononuclear cells showed low sensitivity to treatment. Single bolus injection of the phenolic fraction could delay the growth of established myeloma tumours in syngeneic animals. HPLC and mass spectrometry analysis revealed that the fraction contains gallic acid. However, the biological activity of the fraction differs from the activity of this phenol and hence it should be attributed to other co-purified molecules which remain still unidentified.

Antitumor activity of the intratumoral injection of fowlpox vectors expressing a triad of costimulatory molecules and granulocyte/macrophage colony stimulating factor in mesothelioma

Deficiency in costimulatory molecule expression has been implicated in the ability of tumors to escape immune effectors. The activity of the intratumoral administration of recombinant fowlpox vectors expressing a triad of costimulatory molecules (rF-TRICOM) was evaluated in the asbestos-induced AB12 and AC29 mouse models of mesothelioma. Mesothelioma cell infected with rF-TRICOM expressed high levels of the costimulatory molecules. Prolongation of survival was observed in mice receiving rF-TRICOM in AB12 and AC29 intraperitoneal models. Complete tumor regressions were observed in mice receiving intratumoral rF-TRICOM in the AB12 subcutaneous tumor model. Tumor regressions were associated with the development of serum IgG reactivities to mesothelioma-associated determinants and specific systemic cytolytic activity, and responding mice were capable of rejecting tumors upon re-challenge. Antitumor activity was also observed in mice with established AB12 tumor vaccinated with irradiated rF-TRICOM-infected AB12 cells. The antitumor activity of intratumoral rF-TRICOM was superior to that of the intratumoral injection of a fowlpox vector expressing granulocyte-macrophage colony stimulating factor (rF-GM-CSF). AB12 and AC29 tumors were found to produce GM-CSF and to have substantial macrophage infiltration. Production of GM-CSF decreased in vivo in tumors injected with rF-TRICOM. rF-TRICOM and wild-type fowlpox inhibited the growth of AB12 and AC29 cells in vitro; less inhibition was observed with rF-GM-CSF. These results indicate that the intratumoral injection of rF-TRICOM has significant activity in mouse models of mesothelioma and can elicit a systemic antitumor immune response. The results also suggest potential limitations to the intratumoral administration of cytokines, such as GM-CSF, in mesothelioma.