Yingnian Lu

Mutation-Selective Tumor Remission with Ras-Targeted, Whole Yeast-Based Immunotherapy

Activating mutations in Ras oncoproteins represent attractive targets for cancer immunotherapy, but few vectors capable of generating immune responses required for tumor killing without vector neutralization have been described. Whole recombinant yeast heterologously expressing mammalian mutant Ras proteins were used to immunize mice in a carcinogen-induced lung tumor model. Therapeutic immunization with the whole recombinant yeast caused complete regression of established Ras mutation-bearing lung tumors in a dose-dependent, antigen-specific manner. In combination with the genomic sequencing of tumors in patients, the yeast-based immunotherapeutic approach could be applied to treat Ras mutation-bearing human cancers.

Yeasts encoding tumour antigens in cancer immunotherapy

Immunotherapy for cancer represents an attractive therapeutic target because of its specificity and lack of toxicity, but products investigated so far have been limited by neutralisation, complexity of manufacturing and requirement for patient-specific products. Recombinant yeast cells are capable of stimulating the immune system to produce highly specific and potent cellular responses against target protein antigens with little toxicity. Data from animal models suggest that Tarmogens™ (yeast-based immunotherapeutics) can elicit protective immunity against xenografted and chemically induced tumours. This concept is now being tested in a Phase I trial in patients with colorectal, pancreatic and non-small cell lung cancers.

A Whole Recombinant Yeast-Based Therapeutic Vaccine Elicits HBV X, S and Core Specific T Cells in Mice and Activates Human T Cells Recognizing Epitopes Linked to Viral Clearance

Chronic hepatitis B infection (CHB) is characterized by sub-optimal T cell responses to viral antigens. A therapeutic vaccine capable of restoring these immune responses could potentially improve HBsAg seroconversion rates in the setting of direct acting antiviral therapies. A yeast-based immunotherapy (Tarmogen) platform was used to make a vaccine candidate expressing hepatitis B virus (HBV) X, surface (S), and Core antigens (X-S-Core). Murine and human immunogenicity models were used to evaluate the type and magnitude of HBV-Ag specific T cell responses elicited by the vaccine. C57BL/6J, BALB/c, and HLA-A*0201 transgenic mice immunized with yeast expressing X-S-Core showed T cell responses to X, S and Core when evaluated by lymphocyte proliferation assay, ELISpot, intracellular cytokine staining (ICS), or tumor challenge assays. Both CD4+ and CD8+ T cell responses were observed. Human T cells transduced with HBc18–27 and HBs183–91 specific T cell receptors (TCRs) produced interferon gamma (IFNγ following incubation with X-S-Core-pulsed dendritic cells (DCs). Furthermore, stimulation of peripheral blood mononuclear cells (PBMCs) isolated from CHB patients or from HBV vaccine recipients with autologous DCs pulsed with X-S-Core or a related product (S-Core) resulted in pronounced expansions of HBV Ag-specific T cells possessing a cytolytic phenotype. These data indicate that X-S-Core-expressing yeast elicit functional adaptive immune responses and supports the ongoing evaluation of this therapeutic vaccine in patients with CHB to enhance the induction of HBV-specific T cell responses.

Epidermal growth factor receptor mediates silibinin-induced cytotoxicity in a rat glioma cell line.

Silibinin, derived from milk thistle extract, has been shown to inhibit growth factor receptor-mediated mitogenic and cell survival signaling, and to alter cell cycle regulators. Alteration in pathways regulating cell growth likely account for silibinin’s inhibition of tumor growth. Since the epidermal growth factor receptor (EGFR) is a key regulator in cell signaling pathways, in the present study we directly tested the hypothesis that the EGFR plays a key role in mediating silibinin cytotoxicity to cancer cells. We generated a cell line, 9L-EGFR, which stably expressed human EGFR; the parental rat glioma cell line, 9L, does not contain endogenous EGFR message or protein. Our results show that expression of EGFR was both necessary and sufficient for conferring toxicity in response to silibinin in 9L-EGFR cells. Addition of silibinin was shown to inhibit EGFR activation by EGF in 9L-EGFR cells. These studies support the hypothesis that silibinin toxicity to cancer cells involves the EGFR signaling pathway. The findings presented here provide a rationale for understanding the growth inhibition effect of silibinin in cancer cells, and warrant further investigation into the effect of silibinin on specific pathways of cell signaling mediated by the EGF receptor.