High ROS Production by Celecoxib and Enhanced Sensitivity for Death Ligand-Induced Apoptosis in Cutaneous SCC Cell Lines

Abstract

Incidence of cutaneous squamous cell carcinoma (cSCC) and actinic keratosis has increased worldwide, and non-steroidal anti-inflammatory drugs as celecoxib are considered for treatment. We show here strong anti-proliferative effects of celecoxib in four cSCC cell lines, while apoptosis and cell viability largely remained unaffected. Impeded apoptosis was overcome in combinations with agonistic CD95 antibody or TNF-related apoptosis-inducing ligand (TRAIL), resulting in up to 60% apoptosis and almost complete loss of cell viability. Proapoptotic caspase cascades were activated, and apoptosis was suppressed by caspase inhibition. TRAIL receptor (DR5) and proapoptotic Bcl-2 proteins (Puma and Bad) were upregulated, while anti-apoptotic factors (survivin, XIAP, cFLIP, Mcl-1, and Bcl-w) were downregulated. Strongly elevated levels of reactive oxygen species (ROS) turned out as particularly characteristic for celecoxib, appearing already after 2 h. ROS production alone was not sufficient for apoptosis induction but may play a critical role in sensitizing cancer cells for apoptosis and therapy. Thus, the full therapeutic potential of celecoxib may be better used in combinations with death ligands. Furthermore, the immune response against cSCC/AK may be improved by celecoxib, and combinations with checkpoint inhibitors, recently approved for the treatment of cSCC, may be considered.

Crucial Role of Reactive Oxygen Species (ROS) for the Proapoptotic Effects of Indirubin Derivatives in Cutaneous SCC Cells

“…Thus, the identification of suitable combination partners appears of particular interest. Enhancement of TRAIL-induced apoptosis in cSCC has also previously been shown in combinations with diclofenac and celecoxib [24,33]. As death ligands represent basic elements of an antitumor immune response driven by cytotoxic T-lymphocytes and natural killer cells [6], it is also conceivable that indirubins might enhance an immune response against cSCC in patients.…”

“…A particular role is described here for reactive oxygen species (ROS). Besides their described functions in tissue damaging and aging [22], reactive oxygen species (ROS) can also mediate proapoptotic signaling in cancer cells and may explain the proapoptotic effects of several anticancer therapies, as demonstrated in skin cancer cells [23][24][25]47]. Concerning the activities of indirubin derivatives, we had previously shown ROS production by indirubins in melanoma and CTCL cells.…”

“…Thus, ROS play important roles in different kinds of diseases of the neuronal, cardiovascular and nervous systems, as well as in aging [22]. Furthermore, ROS may contribute to the regulation of apoptosis, as shown in melanoma cells by an iron-substituted nucleoside analogue [23], in cSCC cells for celecoxib [24] and in cutaneous T-cell lymphoma cells (CTCL) for an indirubin derivative [25]. ROS may derive from mitochondrial leakage or other sources [26], but their relation to the described apoptosis pathways is less clear to date.…”

Inhibition of Cell Proliferation and Cell Viability by Sinecatechins in Cutaneous SCC Cells Is Related to an Imbalance of ROS and Loss of Mitochondrial Membrane Potential

“…On the other hand, reactive oxygen species may critically contribute to the induction of apoptosis and other cell death pathways in skin cancer cells, as shown for an iron-substituted nucleoside analogue in melanoma cells [ 50 ], for celecoxib in cSCC cells [ 23 ] and for indirubin derivatives in cutaneous T-cell lymphoma, melanoma and cSCC cells [ 24 , 51 , 52 ]. ROS may derive from mitochondrial leakage or other sources [ 53 ], but their relations to apoptosis pathways are still largely elusive to date.…”

“…Reactive oxygen species are involved in different signaling pathways and play important roles in disease of the neuronal, cardiovascular, and nervous systems as well as in aging [ 22 ]. ROS have been further related to apoptosis induction in cancer cells, as recently shown in cSCC cells for celecoxib [ 23 ] and for indirubin derivatives [ 24 ].…”