Cell death.

Studies have shown that tumor cells are susceptible to pharmacological targeting
of their altered glycolytic metabolism with a variety of compounds that result in
apoptosis. One such compound, 3-bromopyruvate (3-BP), has been shown to eradicate
cancer in an animal model. However, no studies have shown whether the apoptotic
fragments resulting from 3-BP treatment have the capacity to elicit an immunogenic cell
death that activates dendritic cells, the primary antigen presenting cell in the immune
system. Immunogenic cell death is critical to eliciting an effective adaptive immune
response that selectively kills additional target cells and generates immunological
memory. We demonstrated that 3-bromopyruvate induced apoptosis in a number of
different murine breast cancer cell lines, including the highly metastatic 4T1 line. The
dying tumor cells stimulated immature dendritic cells (DCs) of the immortal JAWS II
cell line to produce high levels of the pro-inflammatory cytokine IL-12, and increased their expression of key co-stimulatory molecules CD80 and CD86. The activated
dendritic cells showed increased uptake of fragments from dying tumor cells that
correlated with the increased levels of calreticulin on the surface and release of high
group motility box 1 (HMGB1) of the latter following 3-BP treatment. Additionally, the
anti-phagocytic signal CD47 present on breast cancer cells was reduced by treatment with
3-bromopyruvate when compared to the levels on untreated 4T1 cells. 3-BP treated breast
cancer cells were able to activate dendritic cells through TLR4 signaling. Signaling was
dependent on both the expression of surface calreticulin and on the extracellular release
of high mobility group box 1 protein (HMGB1) during the process of immunogenic cell
death. Killing by 3-BP was compared to mitoxantrone and doxorubicin, among the few
chemotherapeutics that induce immunogenic cell death. 3-BP killing was likewise
compared to camptothecin, a compound that fails to induce immunogenic cell death.
Importantly, 3-BP did not markedly decrease the levels of the key peptide presenting
molecule MHC I on DCs that were co-cultivated with dying tumor cells. Treatment of the
highly aggressive triple negative BT-20 human breast cancer cell line with 3-BP also
induced an immunogenic cell death, activating human dendritic cells in vitro.

In the round worm C. elegans, it has recently been shown that autophagy, a highly
conserved lysosomal degradation pathway that is present in all eukaryotic cells, is
required for maintaining healthspan and for increasing the adult lifespan of worms fed
under dietary restriction conditions or with reduced IGF signaling. It is currently
unknown how extracellular signals regulate autophagy activity within different tissues
during these processes and whether autophagy functions cell-autonomously or nonautonomously.
We have data that for the first time shows autophagy activity in the
neurons and intestinal cells plays a major role in regulating adult lifespan and the
longevity conferred by altered IGF signaling and dietary restriction, suggesting
autophagy can control these phenotypes cell non-autonomously. We hypothesize that
autophagy in the neurons and intestinal cells is an essential cellular process regulated by
different signaling pathways to control wild type adult lifespan, IGF mediated longevity and dietary restriction induced longevity. Excitingly we also have found that in animals
with reduced IGF signaling autophagy can control longevity in only a small subset of
neurons alone. Autophagy in either specific individual chemosensory neurons or a small
group of them is completely sufficient to control IGF mediated longevity. This work
provides novel insight to the function and regulation of autophagy which will help shed
light on understanding this essential process in higher organisms, including mammals.