Analysis of lipids by Raman spectroscopy and mass spectrometry provides a detection tool and mechanistic insight into imatinib resistance in CML-BC

Abstract

Resistance to tyrosine kinase inhibitors (TKIs) is a major challenge in the treatment of chronic myeloid leukemia (CML). Established tests based on the known mechanisms of resistance in the initial chronic phase (CP) confirm resistance, reveal the underlying reason and thereby direct treatment modifications. In the terminal phase of blast crisis (BC), however, additional partially identified mechanisms of resistance exist which necessitates developing modalities to detect resistance regardless of the underlying mechanism and concurrent exploration of the resistance mechanism to assist in identification of appropriate drug targets. In this study both the clinical objectives were achieved by analysing lipids in BC cells, sensitive and resistant to TKIs, using the complementary strengths of distinct analytical technologies.

Raman spectroscopy, through the spectral signatures with lipids as a significant differentiating component could segregate resistant from sensitive cells in the Principal Component Analysis (PCA) and Principal Component based Linear Discriminant Analysis (PC-LDA). This provided a tool to rapidly detect resistance in CML-BC despite unclear mechanism of TKI resistance. The depth of coverage achievable by mass spectrometry allowed the generation of quantitative differential profile of individual lipids in resistant cells. The alterations were in diverse classes of lipids which are involved in cell signalling and inhibition studies could link these alterations to modulation of phospholipase A₂ (PLA₂) levels mediated by p38 mitogen activated protein kinase (p38MAPK), which is causally associated with TKI resistance in CML-BC. Together, lipid analysis using the two platforms, contributed to the detection and mechanistic understanding of imatinib resistance in CML-BC.