Molecular effectors and modulators of hypericin-mediated cell death in bladder cancer cells

Abstract

Photodynamic therapy (PDT) is an anticancer approach utilizing a light-absorbing molecule and visible light irradiation to generate, in the presence of O 2 , cytotoxic reactive oxygen species, which cause tumor ablation. Given that the photosensitizer hypericin is under consideration for PDT treatment of bladder cancer we used oligonucleotide microarrays in the T24 bladder cancer cell line to identify differentially expressed genes with therapeutic potential. This study reveals that the expression of several genes involved in various metabolic processes, stress-induced cell death, autophagy, proliferation, inflammation and carcinogenesis is strongly affected by PDT and pinpoints the coordinated induction of a cluster of genes involved in the unfolded protein response pathway after endoplasmic reticulum stress and in antioxidant response. Analysis of PDT-treated cells after p38 MAPK inhibition or silencing unraveled that the induction of an important subset of differentially expressed genes regulating growth and invasion, as well as adaptive mechanisms against oxidative stress, is governed by this stress-activated kinase. Moreover, p38 MAPK inhibition blocked autonomous regrowth and migration of cancer cells escaping PDT-induced cell death. This analysis identifies new molecular effectors of the cancer cell response to PDT opening attractive avenues to improve the therapeutic efficacy of hypericin-based PDT of bladder cancer.

Photochemically stimulated drug delivery increases the cytotoxicity and specificity of EGF–saporin

“…P38 is also a stress induced kinase (Zarubin & Han 2005) shown to be activated after PDT with different photosensitizers. PDT-induced p38 activation has been reported as a death mechanism as well as a rescuing signal and the impact of p38 signalling on cell death after PDT seems to depend on both the photosensitizer, PDT-dose and the cell line (Klotz et al 1999, Assefa et al 1999, Xue et al 1999, Zhuang et al 2000, Tong et al 2003, Kralova et al 2007, Buytaert et al 2008. Activation of p38 was observed 5 min after LD 50 TPPS 2a -PDT in all investigated cell lines (NuTu-19, WiDr and A-431) (paper IV and VI).…”

ROS-induced autophagy in cancer cells assists in evasion from determinants of immunogenic cell death

“…9,22,23 Phox-ER stress is characterized by the activation of the EIF2AK3-EIF2A-ATF4 branch (EIF2AK3: eukaryotic translation initiation factor 2-alpha kinase 3, also called PKR-like ER kinase; EIF2A: eukaryotic translation initiation factor 2A; and ATF4: activating transcription factor 4) and ERN1-XBP1 branch (ERN1: endoplasmic reticulum to nucleus signaling 1, also called inositol-requiring enzyme 1; XBP1: X-box binding protein 1) of the unfolded protein response; 24 and ultimately culminates into BAX (BCL2-associated X protein) and BAK1 (BCL2-antagonist/killer 1)-dependent mitochondrial apoptosis. 22,23,25 Hyp-PDT-induced ICD 8,16,17 consists of the concomitant preapoptotic emission (30 to 60 min post-PDT, before phosphatidylserine externalization) 9,17 of ATP and CALR through an overlapping molecular trail primarily governed by ROS production, the ER stressassociated kinase EIF2AK3, ER-to-Golgi anterograde transport and class I phosphoinositide-3-kinase (phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha/PIK3CA) activity. 8,9,17 This is followed by late apoptotic (passive) release of chaperones like HSPA1A/HSP70 and HSP90AA1/HSP90.…”

Time-resolved gene expression profiling of human squamous cell carcinoma cells during the apoptosis process induced by photodynamic treatment with hypericin

“…dependent or -independent pathways on one hand, but also activation of survival pathways via p38 MAPK on the other hand (10). Previous studies of our group showed that hypericin-PDT on A-431 cells induced preferentially apoptosis, executed via the mitochondrial pathway activating the caspases 9, 6 and 3, but also caspase 2 of the receptor-mediated pathway, maybe in a feedback loop (11).…”