Carla De Giovanni

2011: the immune hallmarks of cancer

Ten years after the publication of the position paper “The hallmarks of cancer” (Hanahan and Weinberg Cell 100:57–70, 2000), it has become increasingly clear that mutated cells on their way to giving rise to a tumor have also to learn how to thrive in a chronically inflamed microenvironment, evade immune recognition, and suppress immune reactivity. Genetic and molecular definition of these three immune hallmarks of cancer offers the opportunity to learn how to deploy specific countermeasures to reverse the situation in favor of the immune system and, eventually, the patient. This new information could be channeled to address what seem to be the three major hallmarks for the immune control of cancer progression: effective procedures to activate immune reactivity; characterization of not-disposable oncoantigens; and counteraction of immune suppression.

TS/A: a new metastasizing cell line from a BALB/c spontaneous mammary adenocarcinoma

A metastasizing mouse cell line (TS/A), originated from a mammary adenocarcinoma which arose spontaneously in a BALB/c female retired breeder, has been established in vitro. It displayed a remarkable morphologic heterogeneity, which is evident in plastic adherent cultures (cell types ranging from epithelial-like to fibroblast-like) as well as in semi-solid agar cultures. The TS/A line exhibited the presence of specific cytoplasmic estradiol receptor, with a binding activity of 16 fmoles/mg cytosol protein. The in vivo growth pattern was as follows: (1) a s.c. inoculum of 105 cells caused a 100 per cent tumor take and kill in syngeneic animals; mean survival time was 54 + 1 days; (2) it did not show significant transplant immunogenicity in syngeneic animals; (3) it was able to give rise to both spontaneous lung metastases and artificial lung colonies; (4) it had a high capacity to grow in H-2 matched, minor histocompatibility antigen incompatible hosts (106 cells killed 100 per cent DBA/2 mice in 58 + 2 days). This line of spontaneous mammary tumor cells is proposed as a useful model for studies on the heterogeneity of the neoplastic population in relation to metastatic spread, on tumor immunogenicity, and on therapy of mammary neoplasia.

Electroporated DNA Vaccine Clears Away Multifocal Mammary Carcinomas in Her-2/neu Transgenic Mice

The transforming rat Her-2/neu oncogene embedded into the genome of virgin transgenic BALB/c mice (BALB-neuT) provokes the development of an invasive carcinoma in each of their 10 mammary glands. i.m. vaccination with DNA plasmids coding for the extracellular and transmembrane domains of the protein product of the Her-2/neu oncogene started when mice already display multifocal in situ carcinomas temporarily halts neoplastic progression, but all mice develop a tumor by week 43. By contrast, progressive clearance of neoplastic lesions and complete protection of all 1-year-old mice are achieved when the same plasmids are electroporated at 10-week intervals. Pathological findings, in vitro tests, and the results from the immunization of both IFN-gamma and immunoglobulin gene knockout BALB-neuT mice, and of adoptive transfer experiments, all suggest that tumor clearance rests on the combination of antibodies and IFN-gamma-releasing T cells. These findings show that an appropriate vaccine effectively inhibits the progression of multifocal preneoplastic lesions.

Expression of an IGF-I receptor dominant negative mutant induces apoptosis, inhibits tumorigenesis and enhances chemosensitivity in Ewing's sarcoma cells

IGF‐IR plays an essential role in the establishment and maintenance of the transformed phenotype of ES cells and interference with the IGF‐IR pathways causes reversal of the malignant potential of this neoplasm. In this report, we stably transfected a dominant negative IGF‐IR expression plasmid in an ES cell line to determine the effectiveness of this strategy against the in vitro and in vivo growth of ES cells. DXR sensitivity of TC‐71 cells expressing dominant negative mutants of IGF‐IR was also examined. The mutated IGF‐IR that we used carries a mutation in the ATP‐binding domain of the intracellular β subunit, while the extracellular, ligand‐binding α subunit remains unchanged. Cells carrying the dominant mutant IGF‐IR had a marked decrease in proliferation, a significant increase in anoikis‐induced apoptosis and a severely reduced ability to form colonies in soft agar. In vivo, when cells carrying dominant negative IGF‐IR were injected into nude mice, the tumor formation and metastatic abilities of ES cells were reduced and survival increased. Furthermore, transfected clones showed significantly higher sensitivity to DXR, a major drug in the treatment of ES. These results indicate that the IGF/IGF‐IR stimulation of ES cells may be inhibited by expression of mutated IGF‐IR on their surfaces and that this strategy may be considered a possible alternative to impair this important target of ES cells, whose therapeutic potential was further confirmed.

Immunoprevention of Mammary Carcinoma in HER-2/neu Transgenic Mice Is IFN-γ and B Cell Dependent

A vaccine combining IL-12 and allogeneic mammary carcinoma cells expressing p185neu completely prevents tumor onset in HER-2/neu transgenic BALB/c mice (NeuT mice). The immune protection elicited was independent from CTL activity. We now formally prove that tumor prevention is mainly based on the production of anti-p185neu Abs. In the present studies, NeuT mice were crossed with knockout mice lacking IFN-γ production (IFN-γ−/−) or with B cell-deficient mice (μMT). Vaccination did not protect NeuT-IFN-γ−/− mice, thus confirming a central role of IFN-γ. The block of Ab production in NeuT-μMT mice was incomplete. About one third of NeuT-μMT mice failed to produce Abs and displayed a rapid tumor onset. By contrast, those NeuT-μMT mice that responded to the vaccine with a robust production of anti-p185neu Ab displayed a markedly delayed tumor onset. In these NeuT-μMT mice, the vaccine induced a lower level of IgG2a and IgG3 and a higher level of IgG2b than in NeuT mice. Moreover, NeuT-μMT mice failed to produce anti-MHC class I Abs in response to allogeneic H-2q molecules present in the cell vaccine. These findings show that inhibition of HER-2/neu carcinogenesis depends on cytokines and specific Abs, and that a highly effective vaccine can rescue Ab production even in B cell-deficient mice.

Inhibition of Connective Tissue Growth Factor (CTGF/CCN2) Expression Decreases the Survival and Myogenic Differentiation of Human Rhabdomyosarcoma Cells

Connective tissue growth factor (CTGF/CCN2), a cysteine-rich protein of the CCN (Cyr61, CTGF, Nov) family of genes, emerged from a microarray screen of genes expressed by human rhabdomyosarcoma cells. Rhabdomyosarcoma is a soft tissue sarcoma of childhood deriving from skeletal muscle cells. In this study, we investigated the role of CTGF in rhabdomyosarcoma. Human rhabdomyosarcoma cells of the embryonal (RD/12, RD/18, CCA) and the alveolar histotype (RMZ-RC2, SJ-RH4, SJ-RH30), rhabdomyosarcoma tumor specimens, and normal skeletal muscle cells expressed CTGF. To determine the function of CTGF, we treated rhabdomyosarcoma cells with a CTGF antisense oligonucleotide or with a CTGF small interfering RNA (siRNA). Both treatments inhibited rhabdomyosarcoma cell growth, suggesting the existence of a new autocrine loop based on CTGF. CTGF antisense oligonucleotide-mediated growth inhibition was specifically due to a significant increase in apoptosis, whereas cell proliferation was unchanged. CTGF antisense oligonucleotide induced a strong decrease in the level of myogenic differentiation of rhabdomyosarcoma cells, whereas the addition of recombinant CTGF significantly increased the proportion of myosin-positive cells. CTGF emerges as a survival and differentiation factor and could be a new therapeutic target in human rhabdomyosarcoma.

Immunoprevention of HER-2/neu Transgenic Mammary Carcinoma through an Interleukin 12-Engineered Allogeneic Cell Vaccine

This study evaluated the ability of cytokine-engineered allogeneic (H-2q) HER-2/neu-positive cells to prevent tumor development in mammary cancer-prone virgin female BALB/c (H-2d) mice transgenic for the transforming rat HER-2/neu oncogene (BALB-neuT mice). Repeated vaccinations with cells engineered to release interleukin (IL)-2, IL-12, IL-15, or IFN-γ showed that IL-12-engineered cell vaccines had the most powerful immunopreventive activity, with >80% of 1-year-old BALB-neuT mice free of tumors. On the contrary all of the untreated mice and all of the mice vaccinated with IL-12-engineered cells lacking either HER-2/neu or allogeneic antigens developed mammary carcinomas within 22 or 33 weeks, respectively. Whole mount, histology, immunohistochemistry, and gene expression profile analysis showed that vaccination with IL-12-engineered cells maintained 26-week mammary glands free of neoplastic growth, with a gene expression profile that clustered with that of untreated preneoplastic glands. The IL-12-engineered cell vaccine elicited a high production of IFN-γ and IL-4 and a strong anti-HER-2/neu antibody response. Immune protection was lost or markedly impaired in BALB-neuT mice lacking IFN-γ or antibody production, respectively. The protection afforded by the IL-12-engineered cell vaccine was equal to that provided by the systemic administration of recombinant IL-12 in combination with HER-2/neu H-2q cell vaccine. However, IL-12-engineered cell vaccine induced much lower circulating IL-12 and IFN-γ, and therefore lower potential side effects and systemic toxicity.

p185neu protein is required for tumor and anchorage-independent growth, not for cell proliferation of transgenic mammary carcinoma

Transgenic FVB‐NeuN mice (N202) bearing the rat neu protooncogene driven by the mouse mammary tumor virus promoter/enhancer develop focal mammary carcinomas overexpressing the neu‐encoded p185neu protein. In vitro expression of p185neu among mammary carcinoma cultures was heterogeneous, and we could establish some cell lines and clones displaying a complete loss of p185neu expression, along with others with very high p185neu protein level. Upon in vivo injection, p185neu‐positive cells gave rise to fast‐growing tumors with a short latency, while p185neu‐negative cells required a very long latency time, and the resulting tumors were invariably p185neu‐positive. The lower growth ability of p185neu‐negative cells in vivo was also confirmed in athymic nude mice. In vitro, analysis of anchorage‐independent growth in soft agar revealed colony formation from p185neu‐positive but not p185neu‐negative cells. The direct involvement of p185neu in clonogenicity was demonstrated by the inhibition of p185neu‐positive colony growth in soft agar in the presence of an anti‐p185neu monoclonal antibody. By contrast, a higher level of anchorage‐dependent clonogenic growth and proliferation was observed in p185neu‐negative cells as compared to p185neu‐positive cells, thus explaining the relative ease with which p185neu‐negative cell lines and clones were established in vitro. Together, the results indicate that p185neu expression can lead to tumor formation and metastasis through the modification of intrinsic properties of cells related to anchorage‐independent growth ability rather than to proliferation or host‐dependent mechanisms. Int. J. Cancer 87:186–194, 2000.

Concordant morphologic and gene expression data show that a vaccine halts HER-2/neu preneoplastic lesions

While much experimental data shows that vaccination efficiently inhibits a subsequent challenge by a transplantable tumor, its ability to inhibit the progress of autochthonous preneoplastic lesions is virtually unknown. In this article, we show that a combined DNA and cell vaccine persistently inhibits such lesions in a murine HER-2/neu mammary carcinogenesis model. At 10 weeks of age, all of the ten mammary gland samples from HER-2/neu-transgenic mice displayed foci of hyperplasia that progressed to invasive tumors. Vaccination with plasmids coding for the transmembrane and extracellular domain of rat p185neu followed by a boost with rp185neu+ allogeneic cells secreting IFN-gamma kept 48% of mice tumor free. At 22 weeks, their mammary glands were indistinguishable from those of 10-week-old untreated mice. Furthermore, the transcription patterns of the two sets of glands coincided. Of the 12,000 genes analyzed, 17 were differentially expressed and related to the antibody response. The use of B cell knockout mice as well as the concordance of morphologic and gene expression data demonstrated that the Ab response is the main mechanism facilitating tumor growth arrest. This finding suggests that a new way can be found to secure the immunologic control of the progression of HER-2/neu preneoplastic lesions.

The Metastatic Ability of Ewing’s Sarcoma Cells Is Modulated by Stem Cell Factor and by Its Receptor c-kit

Ewings sarcoma is a primitive highly malignant tumor of bone and soft tissues usually metastasizing to bone, bone marrow, and lung. Growth factor receptors and their ligands may be involved in its growth and dissemination. We analyzed the expression of c-kit and its ligand stem cell factor (SCF) in a panel of six Ewings sarcoma cell lines. All cell lines exhibited substantial levels of surface c-kit expression, and five of six displayed transmembrane SCF on the cell surface. Expression of c-kit was down-modulated in all lines by exposure to exogenous SCF. The SCF treatment was able to confer to cells a growth advantage in vitro, due both to an increase in cell proliferation and to a reduction in the apoptotic rate. When used in the lower compartment of a migration chamber, SCF acted as a strong chemoattractant for Ewings sarcoma cells. The pretreatment of cells with SCF reduced their chemotactic response to SCF. In athymic nude mice, Ewings sarcoma cells injected intravenously metastasized to the lung and to a variety of extrapulmonary sites, including bone and bone marrow. Metastatic sites resembled those observed in Ewings sarcoma patients and corresponded to SCF-rich microenvironments. The in vitro pretreatment of cells with SCF strongly reduced the metastatic ability of Ewings sarcoma cells, both to the lung and to extrapulmonary sites. This could be dependent on the down-modulation of c-kit expression observed in SCF-pretreated cells, leading to a reduced sensitivity to the chemotactic and proliferative actions of SCF. Our results indicate that the response to SCF mediated by c-kit may be involved in growth, migration, and metastatic ability of Ewings sarcoma cells.