Inhibiting Cycloxygenase and Ornithine Decarboxylase by Diclofenac and Alpha-Difluoromethylornithine Blocks Cutaneous SCCs by Targeting Akt-ERK Axis

Abstract

Non-melanoma skin cancer (NMSC) is the most common type of skin cancer in Caucasian populations. Its increasing incidence has been a major public health concern. Elevated expressions of ODC and COX-2 are associated with both murine and human NMSCs. Inhibition of these molecular targets singly employing their respective small molecule inhibitors showed limited success. Here, we show that combined blockade of ODC and COX-2 using their potent inhibitors, DFMO and diclofenac respectively abrogates growth of A431 epidermal xenograft tumors in nu/nu mice by more than 90%. The tumor growth inhibition was associated with a diminution in the proliferation and enhancement in apoptosis. The proliferation markers such as PCNA and cyclin D1 were reduced. TUNEL-positive apoptotic cells and cleaved caspase-3 were increased in the residual tumors. These agents also manifested direct target-unrelated effects. Reduced expression of phosphorylated MAPKAP-2, ERK, and Akt (ser473 & thr308) were noticed. The mechanism by which combined inhibition of ODC/COX attenuated tumor growth and invasion involved reduction in EMT. Akt activation by ODC+COX-2 over-expression was the key player in this regard as Akt inhibition manifested effects similar to those observed by the combined inhibition of ODC+COX-2 whereas forced over-expression of Akt resisted against DFMO+diclofenac treatment. These data suggest that ODC+COX-2 over-expression together leads to pathogenesis of aggressive and invasive cutaneous carcinomas by activating Akt signaling pathway, which through augmenting EMT contributes to tumor invasion.

Keratin-6 driven ODC expression to hair follicle keratinocytes enhances stemness and tumorigenesis by negatively regulating Notch

“…Histology, immunohistochemical or immunofluorescence staining of skin and tumor sections were performed according to the standard protocol as described earlier [22]. …”

“…For Western blot analysis, proteins (60–80 μg) were resolved on 4%, 10% and 15% Tris-glycine gel based on their molecular weights and transferred onto a nitrocellulose membrane (Bio-Rad) as described previously [22]. For sequential antibody reprobing, blots were stripped using Restore western blot stripping buffer (Pierce Biotechnology, Rockford, IL, USA) according to manufacturer's instructions.…”

Naproxen Inhibits UVB‐induced Basal Cell and Squamous Cell Carcinoma Development in Ptch1+/−/SKH‐1 Hairless Mice

“…We have shown that increased COX‐2 plays important roles in the pathogenesis of both BCC and SCCs , while COX‐2‐mediated production of PGE 2 plays key roles in tumor progression and metastasis via binding to its receptors EP1‐4, these responses are distinct in BCCs vs SCCs . In addition, we and others have shown that tumor proliferation and reduction in apoptosis by UVB‐induced COX‐2 involve activation of a number of signaling pathways including Akt . Thus, administration of both specific and nonspecific inhibitors of COX‐2 provides benefit in intercepting tumor growth .…”

“…Our laboratory has focused on identifying on various pharmacological targets for the intervention of UVB-induced NMSCs in various murine models. Accordingly, effects of inhibition of pathways such as cyclooxygenase (COX), ornithine decarboxylase, p53, sonic hedgehog, estrogen receptor and Wnt have been described earlier (5)(6)(7)(8)(9)(10)(11)(12).…”

Skin Carcinogenesis Studies Using Mouse Models with Altered Polyamines

“…These data support the use of DFMO as a chemopreventive agent for NMSC and underscore the relevance of the polyamine pathway in skin tumor development. Evidence from animal models using DFMO in combination with polyamine transport inhibitors 172 , 173 or cyclooxygenase (COX) inhibitors 174 , 175 demonstrated increased efficacy in both chemoprevention and therapy of NMSC. In related clinical trials, the combination of DFMO and the COX inhibitor sulindac was both safe and remarkably effective in preventing recurrence of colorectal adenomas in resected adenoma patients followed-up for 3 years, 176 suggesting this would also be a promising combination in individuals at high risk for NMSC such as organ transplant recipients or Xeroderma pigmentosum (XP) patients.…”