Margin assessment during breast conserving surgery using diffuse reflectance spectroscopy.

Significance: During breast-conserving surgeries, it is essential to evaluate the resection margins (edges of breast specimen) to determine whether the tumor has been removed completely. In current surgical practice, there are no methods available to aid in accurate real-time margin evaluation. Aim: In this study, we investigated the diagnostic accuracy of diffuse reflectance spectroscopy (DRS) combined with tissue classification models in discriminating tumorous tissue from healthy tissue up to 2 mm in depth on the actual resection margin of in vivo breast tissue. Approach: We collected an extensive dataset of DRS measurements on ex vivo breast tissue and in vivo breast tissue, which we used to develop different classification models for tissue classification. Next, these models were used in vivo to evaluate the performance of DRS for tissue discrimination during breast conserving surgery. We investigated which training strategy yielded optimum results for the classification model with the highest performance. Results: We achieved a Matthews correlation coefficient of 0.76, a sensitivity of 96.7% (95% CI 95.6% to 98.2%), a specificity of 90.6% (95% CI 86.3% to 97.9%) and an area under the curve of 0.98 by training the optimum model on a combination of ex vivo and in vivo DRS data. Conclusions: DRS allows real-time margin assessment with a high sensitivity and specificity during breast-conserving surgeries.

The Elongin BC Complex Negatively Regulates AXL and Marks a Differentiated Phenotype in Melanoma.

High expression of the receptor tyrosine kinase AXL is implicated in epithelial-to-mesenchymal transition, cancer progression, and therapy resistance. For example, AXL is abundant in BRAF mutant melanomas progressing on targeted BRAF/MEK inhibition. Therefore, AXL is thought to represent an attractive therapeutic target. This notwithstanding, little is known about the mechanisms governing expression of AXL. Here, we describe a FACS-based whole-genome-wide CRISPR-Cas9 screen to uncover regulators of AXL expression. We identified several genes, inactivation of which led to increased AXL expression. Most remarkable was the identification of five components that associate with the Elongin BC heterodimer. Elongin B/C engage in multiple protein-protein interactions, including the transcription factor complex subunit Elongin A, the von Hippel-Lindau (VHL) tumor suppressor protein, and members of the SOCS-box protein family. The screen identified ELOB, ELOC, SOCS5, UBE2F, and RNF7, each of which we demonstrate to serve as an inhibitor of AXL expression. Although the AXL promoter contains hypoxia response elements and Elongin B/C are found in the VHL complex, Elongin B/C unexpectedly regulate AXL independently of hypoxia. Instead, we demonstrate that the Elongin BC complex interacts with AXL through ELOB, and contributes to proteasomal AXL turnover. RNA-sequencing and IHC analyses of melanoma patient-derived xenografts and clinical samples revealed a negative association between Elongin B/C and dedifferentiation. Together, the Elongin BC complex regulates AXL and marks a differentiated melanoma phenotype. IMPLICATIONS: This study identifies the Elongin BC complex as a key regulator of AXL expression and marker of melanoma differentiation.