Drug resistance emergence is a common problem that limits long term outcome benefits in the era of precision cancer therapy. Recently, we identified an early precision drug escape mechanism with adaptive tumor cellular reprogramming emerging within days after drug initiation. Here we present a mass spectrometry imaging (MSI) approach to interrogate the biomolecular changes occurring within residual tumor cells under precision treatment with an ALK-specific kinase inhibitor TAE684 in EML4-ALK fusion (ALK+) lung adenocarcinoma xenograft.

ALK+ H3122 lung adenocarcinoma murine xenograft model was established for in vivo treatment with TAE684, at a daily dose of 25mg/kg by orogastric gavage (n = 6). Diluent control was included as comparison (n = 6). Tumor measurement revealed expected remarkable tumor response with TAE684. Control tumors and drug-treated residual tumor tissues were harvested for MSI studies, at day 7 and day 14 during tumor response. MSI was carried out on formalin fixed, paraffin embedded tissues to compare peptide profiles between control tumors and 7- and 14-day ALK-TKI treated tumors using a histology guided mass spectrometry approach. Briefly, two sections were collected from each sample, one for mass spectrometry and one for histology. Mass spectrometry sections were deparaffinized, antigen retrieved, and subjected to on-tissue tryptic digestion. Tumoral areas of interest (100 μm diameter, ∼20 per sample) were annotated on digital microscopy images of the stained sections. The annotated images were merged with digital images of the unstained sections using Photoshop and this combined image was used to guide data acquisition from the areas of interest. Additionally, frozen control and day 14 TAE684 treated tumors were subjected to full section MSI to determine the ALK inhibitor drug distribution as well as the changing landscape of lipids and metabolites.

Statistical analysis of the peptide data resulted in determination of 580 significant peaks using Wilcoxon rank sum test with a Bonferroni correction. A genetic algorithm classification model consisting of 24 peptide peaks was generated using a leave-20%-out cross validation over 10 iterations that resulted in an overall classification accuracy across the 3 groups of over 98%.

Direct MS/MS fragmentation revealed that TAE684 was detected within the frozen dosed tumors, but was absent from the control tumors. Several lipids (notably, m/z 732.78, 744.67, and 770.72 increased, m/z 769.65 and 820.71 decreased) were found to undergo alterations in expression as a result of TAE684 treatment.

MSI allowed for the direct in situ determination of biomolecules that are changing in expression landscape in ALK+ lung cancer as a result of TAE684 treatment. These results provide a rationale to advance our MSI studies to deepen our insights in mechanisms of adaptive precision drug resistance to improve treatment outcomes.

Citation Format: Erin H. Seeley, Pamela S. Cantrell, Callee M. Walsh, Sijin Wen, Satoshi Komo, Xiaoliang Wu, Wei Zhang, Patrick C. Ma. Mass spectrometry imaging determines biomarkers of early adaptive precision drug resistance in lung cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3874.