Scientific Achievements

PROJECT 3: ROLE OF TNF FAMILY LIGANDS AND THEIR RECEPTORS IN ORAL CARCINOMA DESTRUCTION AND ESCAPE FROM IMMUNE EFFECTOR CELLS

Principal Investigator: Nikola L. Vujanovic, MD, PhD

Scientific Achievements:

We have made the following important observations:

  1. Normal mouse purified, fresh and in vitro cytokine stimulated NK cells and dendritic cells (DC) express transmembrane TNF, Fas ligand and TRAIL, and directly mediate apoptosis against tumor cells.
  2. The apoptotic tumoricidal activity of normal mouse DC could be significantly blocked by individual and, especially, by combined antibodies to TNF, Fas ligand and TRAIL.
  3. Purified, fresh NK cells and DC, obtained from mice deficient in TNF, Fas ligand and LT-α, are impaired in the ability to mediate the apoptotic tumoricidal activity.
  4. Normal mouse cytokine activated NK cells and DC mediated antitumor activity of established subcutaneous tumors, following direct intratumoral injection. In contrast, NK cells and DC of TNF deficient mice are impaired in this function.

These data are fully in agreement with those we have previously obtained with human NK cells, DC, B cells and activated T cells. They confirm that NK cells and DC as well as other major immune cell populations are important antitumor effector cells that are capable of efficiently destroying tumor cells by utilizing the novel tumoricidal mechanism that is mediated by simultaneous engagements of multiple transmembrane TNF family ligands. The in vivo studies demonstrate that this antitumor mechanism is biologically highly important.

Our additional studies have shown that:

  1. Freshly isolated and cultured OC cells express on cell surface low levels of TNFR1, TNFR2, LT-βR, Fas, TRAILR1 and TRAILR2 and are resistant to killing by the corresponding soluble recombinant TNF family ligands.
  2. Normal keratinocytes, normal activated immune cells and freshly-isolated and cultured OC cells produce large quantities of soluble TNFR1 and Fas, while sera of untreated OC patients contain increased levels of soluble TNFR1 and have augmented blocking activity for the TNF family ligand-mediated killing of OC cells by immune cells.

These data indicate that oral carcinoma (OC) cells secrete high levels of soluble TNF family receptors, which can cause the decrease in expression of transmembrane TNF family receptors and consequently resistance of OC cells to immune cell-mediated destruction. In addition, the secreted TNF family receptors can bind to transmembrane TNF family ligands on immune cells and cause the impairment of TNF family ligand-mediated immune destruction of cancer cells in OC patients.

We have also determined that:

  1. Immune cells of OC patients express increased levels mRNAs, but decreased levels of transmembrane TNF, FasL and TRAIL proteins; and that sera of these patients contain augmented levels of TNF.
  2. Immune cells are impaired in the ability to mediate killing of OC cells via TNF family ligands.
  3. Soluble TNFR1 binds in vivo to transmembrane TNF expressed on PBMNL. The bound soluble TNFR1 can be released in vitro by low pH or high osmomolarity. The release of soluble TNFR1 from transmembrane TNF leads to the increase of tumoricidal activity of the immune cells.

These data indicate that immune effector cells of OC patients are impaired in killing of OC cells. They also suggest that this impairment could be caused by the increased secretion of soluble TNF family ligands and/or augmented blocking of transmembrane TNF family ligands with soluble TNF family receptors.

Related Publications:

Janjic BM, Lu G, Pimenov A, Whiteside TL, Storkus WJ, Vujanovic NL: Innate direct anticancer effector function of human immature dendritic cells. I. Involvement of a potent apoptosis-inducing pathway. J Immunol 168: 1823-1830, 2002.
Lu G, Janjic BM, Janjic J, Whiteside TL, Storkus WJ, Vujanovic NL: Innate direct anticancer effector function of human immature dendritic cells. II. Role of TNF, LT-α1β2, Fas ligand and TRAIL. J Immunol 168, 1831-1839, 2002.
Li S, Xu J, Makarenkova VP, Tjandrawan T, Vakkila J, Reichert T, Gooding W, Lagenaur CF, Achim CL, Chambers WH, Herberman RB, Whiteside TL, Vujanovic NL: A novel epitope of N-CAM defines precursors of human adherent NK cells. J Leuk Biol, in press, 2004.
Vujanovic NL: Testing natural killer cells to predict cancer outcome. In Measuring Immunity: The Immunology Surrogates Handbook, Lotze MT and Thomson AW (eds): Academic Press, in press, 2004.
Vujanovic NL, Makarenkova VP, Popovic P, Lu G, Chakrabarti AK, Watkins S: Are TNF family ligands critical mediators of dendritic cell-NK cell interaction. J Leuk Biol (Conceptual paper), submitted 2004.