ABSTRACT

In this work, we investigated the anticancer activity of orally administered recombinant human lactoferrin (rhLF) alone and in combination with chemotherapy in tumor-bearing mice. rhLF inhibited the growth of squamous cell carcinoma (O12) tumors in T cell-immunocompromised nu/nu mice by 80% when administered at 1,000 mg/kg (2.9 g/m 2 ) by oral gavage twice daily for 8 days (p < 0.001). Similar activity was observed in syngeneic, immunocompetent BALB/c mice, where orally administered rhLF (1,000 mg/kg, 2.9 g/m 2 once daily) halted the growth of mammary adenocarcinoma TUBO. Oral rhLF (200 mg/kg, 0.57 g/m 2 ) was also used alone and in combination with cis-platinum (5 mg/kg) to treat head-and-neck squamous cell carcinoma in a syngeneic murine model. Monotherapy with oral rhLF or cis-platinum caused 61% or 66% tumor growth inhibition over placebo, respectively. Mice receiving both therapies showed 79% growth inhibition, a statistically significant improvement over each drug alone. We then demonstrated that administration of oral rhLF (300 mg/kg, 0.86 g/m 2 ) to tumor-bearing or naive mice resulted in (i) significantly increased production of IL-18 in the intestinal tract, (ii) systemic NK cell activation and (iii) circulating CD8 ؉ T-cell expansion. These data suggest that oral rhLF is an immunomodulatory agent active against cancer as a single agent and in combination chemotherapy, exerting its systemic effect through stimulation of IL-18 and other cytokines in the gut enterocytes. rhLF has been administered orally to 211 people without a single serious drug-related adverse event. Thus, rhLF shows promise as a safe and well-tolerated novel immunomodulatory anticancer agent.

Lactoferrin (LF) is an important protein component of the innate immune system that is broadly distributed within the body fluids. LF is endowed with multiple biological activities. Talactoferrin (TLF), a recombinant human LF, is in clinical development as an anticancer agent and is entering Phase III clinical trials. Here, we show that TLF induces the maturation of human dendritic cells (DCs) derived from monocytes. TLF, at physiologically relevant concentrations (100 microg/ml) up-regulates the expression of human leukocyte antigen (HLA) class II, CD83, CD80, and CD86 costimulatory molecule and CXCR4 and CCR7 chemokine receptors, acting primarily through the p38 MAPK signaling pathway. DCs matured by TLF displayed an enhanced release of IL-8 and CXCL10, as well as a significantly reduced production of IL-6, IL-10, and CCL20. They also display a reduced ability to take up antigen and increased capacity to trigger proliferation and release IFN-gamma in the presence of allogeneic human T cells. TLF-matured DCs are able to prime naive T cells to respond to KLH antigen and display a significantly increased capacity to present Flu-MA(58-66) peptide to HLA-A2-matched T cells. These data suggest that a key immunomodulatory function that may be mediated by TLF is to link the innate with adaptive immunity through DC maturation.

To assess the role of CD4 + CD25 + Foxp3 + regulatory T (Treg) cells in overcoming immunosurveillance of Erbb2 (HER-2/ neu) mammary lesions, we studied the effects of their sustained removal in BALB/c female mice made transgenic for the rat Erbb2 (r-Erbb2) oncogene (BALB-neuT mice), which develop multiple mammary carcinomas. During the progression of these lesions, Treg cells expand in the spleen, tumor draining lymph nodes, and tumors. Repeated administration of anti-CD25 antibodies extends tumor-free survival, reduces carcinoma multiplicity, and leads to the manifestation of a natural antibody and CTL-mediated reactivity against r-Erbb2. Loss of Foxp3 + Treg cells during anti-CD25 treatment remarkably caused the disappearance of Gr1 + immature myeloid cells, suggesting a cross-talk between these two inhibitory immune cell types. Treg cell expansion associated with r-Erbb2 overexpression may be seen as a physiologic response to dampen the immune reaction elicited by local anomalous overexpression of a self-antigen. (Cancer Res 2006; 66(15): 7734-40)