Jacob Hochman

Maternal immunization is an important tool directed against a variety of infectious maladies in the offspring. A complementary, but less explored area is the use of maternal immunization in the prevention and treatment of childhood cancers. This in part stems from the lack of adequate experimental model systems. Lymphomas of the Central Nervous System (CNS) and ocular involvement pose a therapeutic challenge. Ocular lymphoma is a lethal disease caused mainly by two clinically distinct forms of non-Hodgkin’s lymphoma: non-Hodgkin’s lymphoma of the central nervous system, or Primary CNS lymphoma (PCNSL), and systemic lymphoma metastatic to the eye. Previously, we developed an experimental model whereby mouse lymphoma cell variants, derived from the S49 T-cell lymphoma, metastasized to the CNS and eyes following Intraperitoneal inoculation at days 7-10 postnatal. Here, we extended the model to study whether maternal immunization can impede CNS/Ocular metastasis in the offspring exposed to the metastatic lymphoma cells. To that effect, female Balb/C mice were vaccinated with either immunogenic, live, S49 lymphoma cell variants, or with a purified protein antigen: the 98 amino acid signal peptide of the envelop precursor protein of Mouse Mammary Tumor Virus (MMTV) endogenously harbored by the S49 lymphoma. The offspring from both vaccination protocols were immunized against a challenge with the CNS/Ocular metastatic lymphoma cells. Immunity was conferred via milk suckling and was prolonged without further challenge for an extended period of at least 3 months. The abovementioned findings constitute a novel experimental model system whereby CNS/Ocular metastasis of malignant lymphoma in the offspring is impeded through maternal vaccination/immunization and thus, can be followed mechanistically as well as for novel therapeutic modalities.

An increasing body of evidence in recent years supports an association of the betaretrovirus mouse mammary tumor virus (MMTV) with human breast cancer. This is an issue that still raises heated controversy. We have come to address this association using the signal peptide p14 of the MMTV envelope precursor protein as a key element of our strategy. In addition to its signal peptide function, p14 has some significant post endoplasmic reticulum (ER)-targeting characteristics: (1) it localizes to nucleoli where it binds key proteins (RPL5 and B23) involved (among other activities) in the regulation of nucleolar stress response, ribosome biogenesis and p53 stabilization; (2) p14 is a nuclear export factor; (3) it is expressed on the cell surface of infected cells, and as such, is amenable to, and successfully used, in preventive vaccination against experimental tumors that harbor MMTV; (4) the growth of such tumors is impaired in vivo using a combination of monoclonal anti-p14 antibodies or adoptive T-cell transfer treatments; (5) p14 is a phospho-protein endogenously phosphorylated by two different serine kinases. The phosphorylation status of the two sites determines whether p14 will function in an oncogenic or tumor-suppressing capacity; (6) transcriptional activation of genes (RPL5, ErbB4) correlates with the oncogenic potential of MMTV; (7) finally, polyclonal anti-p14 antibodies have been applied in immune histochemistry analyses of breast cancer cases using formalin fixed paraffin-embedded sections, supporting the associations of MMTV with the disease. Taken together, the above findings constitute a road map towards the diagnosis and possible prevention and treatment of MMTV-associated breast cancer.

Due to the toxicity of platinum compounds used in the clinic as anticancer chemotherapies, titanium serves as a safe and attractive alternative. Lately, we introduced a new family of Ti complexes based on readily available phenolato ligands, demonstrating incredibly high hydrolytic stability, with the lead compound phenolaTi demonstrating wide cytotoxic activity toward the NCI‐60 panel of human cancer cell lines, with an average GI₅₀value of 4.7±2 μm. Herein, we evaluated in vivo: a) the safety, and b) the growth inhibitory capacity (efficacy) of this compound. PhenolaTi was found to be effective in vivo against colon (CT‐26) and lung (LLC‐1) murine cell lines in syngeneic hosts and toward a human colon cancer (HT‐29) cell line in immune‐deficient (Nude) mice, with an efficacy similar to that of known chemotherapy. Notably, no clinical signs of toxicity were observed in the treated mice, namely, no effect on body weight, spleen weight or kidney function, unlike the effects observed with the positive control Pt drugs. Studies of combinations of phenolaTi and Pt drugs provided evidence that similar efficacy with decreased toxicity may be achieved, which is highly valuable for medicinal applications.

A new Immunization and treatment strategy for mouse mammary tumor virus (MMTV) associated cancers

Titanium(IV) complexes exhibit high potential as anti-tumor agents, particularly due to their low intrinsic toxicity and cytotoxicity toward cisplatin resistant cells. Nevertheless, Ti(IV) complexes generally undergo rapid hydrolysis that previously hampered their utilization as anticancer drugs. We recently overcame this difficulty by developing a highly stable Ti(IV) complex that is based on tetra-phenolato, hexadentate ligand, formulated into organic nanoparticles. Herein we investigated the activity of this complex in vitro and in vivo. Although inactive when tested directly due to poor solubility, when formulated, this complex displayed (a) high cytotoxicity toward cisplatin resistant human ovarian cells, A2780-cp, with resistance factor of 1.1; (b) additive behavior in combination with cisplatin toward ovarian and colon cancer cells; (c) selectivity toward cancer cells as implied by its mild activity toward non-cancerous, fibroblast lung cells, MRC-5; (d) high stability and durability as manifested by the ability to maintain cytotoxicity, even following one week of incubation in 100% aquatic medium solution; and (e) in vivo efficacy toward solid tumors of human colon cancer cells, HT-29, in nude mice without any clinical signs of toxicity. These features support the formulated phenolato Ti(IV) complex being an effective and selective anti-tumoral agent.

Nanoparticles of titanium(IV) complexes of phenolato ligands were formed and evaluated for cytotoxicity toward human HT‐29 colon cancer, murine T‐25 lymphoma, and murine HU‐2 multidrug‐resistant (MDR) cells. The nano‐formulation, besides increasing the complexes′ shelf lives, is particularly efficient in overcoming limitations in solubility and cell‐penetration, thus enhancing biological accessibility; large complexes that were inactive when measured in a non‐formulated form showed marked activity when nano‐formulated. For active and accessible small complexes, the effect of the formulation was negligible. Most complexes showed similar activity toward MDR cells and their drug‐sensitive analogues, further increasing their therapeutic potential. An exception is a particularly hydrophobic complex, which is presumably more accessible to interaction with the membrane ABCB1 (MDR1) transporter active in the multidrug resistance of HU‐2 cells. The most efficient compound is a mononuclear complex of a single hexadentate ligand, combining particularly high activity and hydrolytic stability with accessibility aided by the nano‐formulation.