Balancing life with glycoconjugates: monitoring unfolded protein response-mediated anti-angiogenic action of tunicamycin by Raman Spectroscopy

N-acetylglucosaminyl 1-phosphate transferase: an excellent target for developing new generation breast cancer therapeutic

Studies from our laboratory have explained that breast tumor progression can be attenuated by targeting the N-linked glycoproteins of the tumor microvasculature and that of tumor cells alike with a protein N-glycosylation inhibitor, tunicamycin. Absence of N-glycosylation leads to an accumulation of un- or mis-folded proteins in the ER and the cell develops “ER stress”. The result is cell cycle arrest, and induction of apoptosis mediated by unfolded protein response (upr ) signaling. Tunicamycin inhibited in vitro and in vivo (Matrigel™ implants in athymic nude mice) angiogenesis in a dose dependent manner. The action is irreversible and survived under tumor microenvironment, i.e., in the presence of FGF-2 or VEGF or higher serum concentration. Importantly, tunicamycin prevented the progression of double negative (ER-/PR-/Her2+) and triple negative (ER-/PR-/Her2-) breast tumors by ∼55% - 65% in three weeks in athymic nude mice [Balb/c(nu/nu )]. Analyses of paraffin sections exhibited “ER stress” in both microvasculature and in tumor tissue.

Nanoformulation enhances anti-angiogenic efficacy of tunicamycin

Nanoparticles (<100 nm) evades the immune system's clearing mechanisms long enough to reach the targeted disease tissue efficiently. We have, therefore, hypothesized that nano-formulated Tunicamycin would have a better efficacy and consequently it will be a better candidate for treating solid tumor including breast cancer in the clinic. Tunicamycin, a potent inhibitor of asparagine-linked (N-linked) protein glycosylation has been found earlier (I) inhibits angiogenesis in vitro by arresting cells in G1; (II) in vivo angiogenesis in Matrigel™ implant in nude mice; and (III) prevents the progression of a double- and a triple-negative breast tumor in athymic nude mice by inducing "ER stress" in tumor microvasculature. Tunicamycin could work alone or in combination with radiation/radiotherapy. To evaluate nano-formulated Tunicamycin, we have synthesized Tunicamycin encapsulated in peptide nanotubes, nanotubes bound to gold nanoparticles (Au NPs) conjugated with Tunicamycin, Tunicamycin conjugated with nanotubes, Au NPs bound to tubes and conjugated with Tunicamycin, and Au NPs conjugated with Tunicamycin. Functionalization of the nanoparticles was characterized by transmission electron microscopy (TEM), Fourier Transformed Infrared (FTIR) Spectroscopy, dynamic light scattering, atomic force microscopy (AFM), and absorbance spectroscopy. The 3-(4,5-methylthiazol-2-yl)-2,5-dipheyl-tetrazolium bromide (MTT) assay indicated that nanoparticles (1 μg/mL) inhibited capillary endothelial cells proliferation, i.e., angiogenesis ~50% within one hour of treatment whereas the native Tunicamycin had no effect. The nano-formulated Tunicamycin blocked the cell cycle progression by inhibiting either both cyclin D1 and CDK4, or cyclin D1, or the CDK4 expression as well as the expression of phospho Rb (serine-229/threonine-252). Phosphorylation of p53 at serine-392 was down-regulated but not the total p53. Increased expression of GRP-78/Bip identified "ER stress". Upregulated expression (1.6-5.5 fold) of phopsho-PERK and significant reduction of mannosylphospho dolichol synthase (DPMS) expression supported induction of unfolded protein response (upr) signaling. Down regulated expression of caspase-9 and caspase-3 proposes a non-canonical pathway of cell death during "ER stress" induced by nano-formulated Tunicamycin.