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Digital Image Correlation (DIC) is an optical measurement technique that can easily be adapted for high magnification applications. These high magnifications involve competing phenomena which must be balanced to produce the highest quality measurements. When out-of-plane displacements cause the specimen under investigation to move out of the depth of field, poor focus negatively affects the measurement. As a result, it is often recommended to reduce aperture size to improve the depth of field. However, smaller aperture sizes can also cause poor focus as the diffraction limit of light causes larger Airy disks, particularly at longer working distances. This work investigates the competing effects of both depth of field and Airy disk size in three test cases: higher magnification and shorter working distance, lower magnification and shorter working distance, and lower magnification and longer working distance. Different aperture sizes are found to change which effect dominates, and a recommendation for selecting the aperture setting to minimize measurement error from both phenomena is made.

Basal cell carcinoma (BCC) is the most common skin malignancy. Deregulated hedgehog signaling plays a central role in BCC development; therefore hedgehog inhibitors have been approved to treat locally advanced or metastatic BCC. However, the development of resistance to hedgehog inhibitors is the major challenge in effective treatment of this disease. Herein, we evaluated the efficacy of a natural agent silibinin to overcome resistance with hedgehog inhibitors (Sant-1 and GDC-0449) in BCC cells. Silibinin (25–100 μM) treatment for 48 hrs strongly inhibited growth and induced death in ASZ001, Sant-1 resistant (ASZ001-Sant-1) and GDC-0449 resistant (ASZ001-GDC-0449) BCC cells. Furthermore, colony forming ability of ASZ001, ASZ001-Sant-1 and ASZ001-GDC-0449 cells was completely inhibited by silibinin treatment. Molecular analysis showed that silibinin treatment decreased the level of phosphorylated-EGFR (Tyrosine-1173) and total EGFR in ASZ001-Sant-1 cells; key signaling molecules responsible for BCC resistance towards hedgehog inhibitors. Further, silibinin treatment decreased the phosphorylated-Akt (Serine-473), phosphorylated-ERK1/2 (Threonine 202/Tyrosine 204), cyclin D1 and Gli-1 level but increased the SUFU expression in ASZ001-Sant-1 resistant cells. Silibinin treatment of ASZ001-Sant-1 resistant cells also decreased bcl-2 but increased cleaved caspases 3 and PARP cleavage, suggesting induction of apoptosis. Together, these results support silibinin use to target hedgehog inhibitors resistant BCC cells.

Non-melanoma skin cancers (NMSCs) account for about half of all malignancies diagnosed annually in the United States. Around 80% of NMSCs are basal cell carcinoma (BCC) and 20% are squamous cell carcinoma (SCC). Whereas the efficacy of several chemopreventive agents has been examined and reported against both BCC and SCC, a majority of these studies have focused on the test agent’s activity in a long-term setting to determine the amount of tumors formed. Notably, the studies evaluating the efficacy of chemopreventive agents during early stage/s of BCC development are lacking. Accordingly, utilizing the well-established patched (Ptch)+/- mouse model of UVB-induced BCC formation, we excised skin samples from UVB exposed mice prior to tumor formation to study the promotion/progression of BCC and to determine the target/s of silibinin, a well-known skin cancer (SCC) chemopreventive agent, in tumor growth inhibition. Ptch+/- and Ptch+/+ mice were irradiated with UVB 240mJ/cm2 3 times per week with or without topically applied silibinin 5 times per week. As early as one month, we found that UVB exposure significantly increased the number of mast cells in Ptch+/- mice by about 48% (P Citation Format: Cynthia M. Rigby, Gagan Deep, Anil K. Jain, David J. Orlicky, Chapla Agarwal, Komal Raina, Rajesh Agarwal. Silibinin inhibits UVB-induced promotion and progression of microscopic basal cell carcinoma formation via targeting bone morphogenic protein 2 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5088.

Non-melanoma skin cancers (NMSC) are a growing problem given that solar ultraviolet B (UVB) radiation exposure is increasing most likely due to depletion of the atmospheric ozone layer and lack of adequate sun protection. Better preventive methods are urgently required to reduce UV-caused photodamage and NMSC incidence. Earlier, we have reported that silibinin treatment activates p53 and reduces photodamage and NMSC, both in vitro and in vivo; but whether silibinin exerts its protective effects primarily through p53 remains unknown. To address this question, we generated p53 heterozygous (p53+/-) and p53 knockout (p53-/-) mice on SKH-1 hairless mouse background, and assessed silibinin efficacy in both short- and long-term UVB exposure experiments. In the chronic UVB-exposed skin tumorigenesis study, compared to p53+/+ mice, p53+/- mice developed skin tumors earlier and had higher tumor number, multiplicity and volume. Silibinin topical treatment significantly reduced the tumor number, multiplicity and volume in p53+/+ mice but silibinin' protective efficacy was significantly compromised in p53+/- mice. Additionally, silibinin treatment failed to inhibit precursor skin cancer lesions in p53-/- mice but improved the survival of the mice. In short-term studies, silibinin application accelerated the removal of UVB-induced DNA damage in p53+/+ mice while its efficacy was partially compromised in p53-/- mice. Interestingly, silibinin treatment also inhibited the UVB-induced inflammatory markers in skin tissue. These results further confirmed that absence of the p53 allele predisposes mice to photodamage and photocarcinogenesis, and established that silibinin mediates its protection against UVB-induced photodamage, inflammation and photocarcinogenesis partly through p53 activation.