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Detection of a Circulating MicroRNA Custom Panel in Patients with Metastatic Colorectal Cancer
Published on: March 14, 2019
Detecting microsatellite instability in cancer via multiplexed orthogonal gap-enhanced Raman tags
Guowei Fu1,2, Jin Li2, Qian Zhang3
1Guangdong Provincial Key Laboratory of Large Animal Models for Biomedicine, School of Pharmacy and Food Engineering, Wuyi University 529020 Jiangmen China wyuchemwrh@126.com.
Abstract:
Microsatellite instability (MSI) is a hallmark of colorectal cancer in immunotherapy, whose phenotypes mainly involve four mismatch repair (MMR) proteins (MlH1, MSH2, MSH6 and PMS2). Since these MMR proteins are highly interdependent, simultaneous detection of these proteins rather than separate detection in cancer is vital to accurately distinguish the MSI phenotypes. In this study, we fabricated four orthogonal gap-enhanced Raman tag (O-GERT) flavors with high sensitivity, superb photostability, and completely separated interference-free signal readouts. With antibody functionalization, these multicolored O-GERTs allowed one-shot detection of these four MMR proteins in cancer tissues with high specificity and spectral resolution. Based on quantitative Raman imaging, these cancer tissues were classified into microsatellite stable (MSS) or high-frequency MSI (MSI-H) subtypes. The detected MSI-H ratios for colorectal, breast and gastric cancers were 13.3%, 6.7% and 3.3%, respectively. Moreover, the correlation between the expression levels of these MMR proteins in colorectal cancer and related clinicopathologic parameters in these subtypes was established for the first time. We further demonstrated that MSI in cancer can serve as a tool for screening Lynch syndrome (a genetic disorder) and predicting potential candidates for immunotherapy by PD1/PD-L1 blockade. To the best of our knowledge, this is the first example of quantitative multiplexed Raman imaging for fast detection of MSI in cancer.
Insights
This study introduces a novel method for detecting four key mismatch repair (MMR) proteins simultaneously in cancer tissues, crucial for identifying microsatellite instability (MSI) phenotypes and guiding immunotherapy.
Area of Science:
- Biomedical Engineering
- Molecular Oncology
- Spectroscopy
Background:
- Microsatellite instability (MSI) is a critical biomarker in cancer, particularly colorectal cancer, influencing immunotherapy response.
- Accurate MSI phenotyping relies on the interdependent expression of four mismatch repair (MMR) proteins: MLH1, MSH2, MSH6, and PMS2.
- Current detection methods often lack the ability for simultaneous, high-resolution analysis of these interdependent proteins.
Purpose of the Study:
- To develop a sensitive and specific method for simultaneous detection of four MMR proteins in cancer tissues.
- To classify cancer subtypes based on microsatellite stable (MSS) or high-frequency MSI (MSI-H) status using quantitative Raman imaging.
- To establish correlations between MMR protein expression and clinicopathologic parameters, and explore MSI's role in Lynch syndrome screening and immunotherapy prediction.
Main Methods:
- Fabrication of four orthogonal gap-enhanced Raman tag (O-GERT) flavors with distinct, interference-free spectral readouts.
- Antibody functionalization of O-GERTs for specific, one-shot detection of MLH1, MSH2, MSH6, and PMS2 proteins.
- Quantitative Raman imaging for classifying cancer tissues into MSS or MSI-H subtypes and analyzing MMR protein expression.
Main Results:
- Achieved high sensitivity, photostability, and specificity in detecting the four MMR proteins.
- Successfully classified colorectal, breast, and gastric cancer tissues into MSS or MSI-H subtypes with detected MSI-H ratios of 13.3%, 6.7%, and 3.3%, respectively.
- Established novel correlations between MMR protein expression and clinicopathologic parameters in colorectal cancer subtypes.
Conclusions:
- Quantitative multiplexed Raman imaging offers a fast and accurate approach for MSI detection in various cancers.
- This technique facilitates MSI phenotyping, aiding in Lynch syndrome screening and identifying candidates for PD1/PD-L1 blockade immunotherapy.
- The simultaneous detection of interdependent MMR proteins provides a more comprehensive understanding of MSI status in cancer.
