14-3-3σ/Stratifin Expression in HK1.Ras/Fos-Δ5ptenflx Transgenic Mouse Skin Carcinogenesis Reveals an Early, Inhibitory Role; Lost During MDM2 Activated/P53 Inactivated Malignant Progression

The mechanisms driving or inhibiting skin carcinogenesis depend upon the contexts created by temporal acquisition of each mutation when pitted against the sentinel systems that have evolved to resist progression at each stage. To model this process, transgenic mice have been established that express activated rasHa and fos oncogenes together with RU486-inducible [K14.creP/lox-P] PTEN [5PTENflx] mutation exclusively in the epidermis. HK1.ras/fos/Δ5PTEN mice exhibit papillomas that convert to well-differentiated SCC following p53 loss and progress to SCCs following subsequent p21 loss/p-AKT1 activation. In addition, recently a suprabasal-to-basal increase in MDM2 activation [p-MDM2166] was observed associated with this p53 loss. Thus, given that 14-3-3σ/stratifin is a chaperone protein which removes/relocates MDM2 for degradation, 14-3-3σ/stratifin expression status in papillomatogenesis and progression to carcinoma was investigated. Already 14-3-3σ/Stratifin is known to play pivotal roles in keratinocyte growth, differentiation, and carcinogenesis but its exact protective [or potentially oncogenic] functions in differing tumour contexts remain unclear, as some studies show that 14-3-3σ/stratifin acts as a tumour suppressor and loss drives cancer; whilst others show increased expression associates with tumour invasion. Initially, compared to normal skin, RU486-treated tri-genic ras/fos/PTENflx epidermis expressed elevated 14-3-3σ/stratifin in resultant hyperplasia, and 14-3-3σ/stratifin remained strongly expressed in both basal and suprabasal layers of p53+ve /p21+ve papillomas. However, 14-3-3σ/stratifin expression diminished following malignant conversion, concomitant with p53 loss but persistent p21 expression. New HK1.ras/fos/5PTEN data demonstrate that this 14-3-3σ reduction/loss in basal layer keratinocytes was also associated with the suprabasal-to-basal expression of activated p-MDM2166; consistent with a mechanism of reduced basal layer p53 expression driving the susceptibility of late-stage papillomas to malignant conversion. Further, in 3D living skin assays, reduction/loss in 14-3-3σ expression was associated with an increased invasive potential. Collectively these data suggest that, in this context, 14-3-3σ plays important tumour suppressive roles in papillomas which inhibit MDM2 function and help maintain p53. However, diminished 14-3-3σ expression may facilitate MDM2-mediated loss of p53 which aids malignant conversion

Measuring the Prong Velocity of Quartz Tuning Forks Used to Probe Quantum Fluids

Recently, quartz tuning forks have been used to probe the dynamics of quantum fluids. For many of these measurements it is important to know the velocity amplitude of the tips of the vibrating fork prongs. We have used different techniques to establish, with an accuracy of a few percent, the relationship between the electrical and mechanical properties of several commercial quartz tuning forks with fundamental resonant frequency similar to 32 kHz. The velocity is usually inferred from an electro-mechanical calibration that models a quartz prong as a clamped, rectangular cantilever beam. We have tested the accuracy of this calibration using three methods: measurement of the amplitude at which the fork prongs touch each other; direct optical measurement of the moving fork prongs using strobe microscopy; and a Michelson interferometry technique operating with a 670 nm laser. All three methods yield consistent results. The velocity so determined is found to be 10% lower than that of the standard electro-mechanical calibration