P500 - The Dynamic Variation of Serum Proteins in Non-metastatic Mismatch Repair Deficient Colorectal Cancer with PD-1 Checkpoint Inhibitors Treatment

Purpose/Background: The outstanding survival benefits were achieved by PD1 checkpoint inhibitors in metastatic mismatch repair deficient (dMMR) or microsatellite instability-high (MSI-H) colorectal cancer, this application has been expanded to non-metastatic dMMR/MSI-H colorectal cancer. Relevant studies have shown that neoadjuvant immunotherapy has demonstrated excellent therapeutic effects on non-metastatic dMMR/MSI-H colorectal cancer, with pathological complete response rates and clinical complete response rates exceeding 70%. However, the immune-related adverse events (irAEs) induced by immunotherapy cannot be ignored. Currently, there remains an urgent need to investigate methods for effectively predicting immunotherapy efficacy and identifying potential targets to enhance therapeutic outcomes. Therefore, this study will detect the dynamic changes of serum proteins in non-metastatic dMMR/MSI-H colorectal cancer during immunotherapy and explore potential protein markers for predicting therapeutic effects.

Methods/Interventions: This study included 21 cases of non-metastatic dMMR/MSI-H colorectal cancer treated by PD1 checkpoint inhibitors. According to the evaluation of computed tomography (CT), magnetic resonance imaging (MRI), and digestive endoscopy, tumors with immunotherapy were effectively evaluated by the RECIST 1.1 classification. In the group with complete response (CR), achieving pathological complete response (pCR) and clinical complete response (cCR) within less than 4 treatment cycles were Early-CR, while those with more than 4 cycles were Late-CR. Serum samples of these patients before and after immunotherapy will be collected and tested using Olink Proteomics.

Results/Outcomes: A total of 21 patients with non-metastatic dMMR/MSI-H colorectal cancer were treated with PD1 checkpoint inhibitors. After immunotherapy, 15 patients (71.4%) achieved cCR or pCR, and 6 patients (28.6%) reached partial response (PR). Furthermore, A total of 3,072 proteins were explored by using Olink Proteomics. The results indicated that the increasing expression of 843 proteins and decreasing expression of 16 were detected in the serum of post-treatment as compared to the serum of pre-treatment. The proteins of PDCD1, GDF2, ALCAM, SUSD2, and ADGRG2 gradually increased during the process of immunotherapy. The proteins of IL6 and NOS2 continuously increased in the process of dMMR colorectal cancer with PD-1 treatment. Protein expression cluster analysis showed that there was a significant difference in protein expression between the good response group and the poor response group before immunotherapy. Among differential proteins, AKR1C4 (AUC=0.912), BPIFB2 (AUC=0.990), NEFL (AUC=0.912), RCOR1 (AUC=0.882), and FGF21 (AUC=0.882) can be used as serum protein markers with poor immunotherapy effects. CNTN5 (AUC=0.971), BPIFA2 (AUC=0.804), GH2 (AUC=0.814), IL7R (AUC=0.902), and TNFSR12 (AUC=0.882) can be used as serum protein markers with good immunotherapy effects.

Conclusion/Discussion: Non-metastatic dMMR/MSI-H colorectal cancer could benefit from immunotherapy. Our work showed that nearly 70% of patients could achieve pCR or cCR, and 100% of patients (CR+PR) have a good response to immunotherapy. Serum protein detection may effectively predict the effect of PD-1 treatment before immunotherapy. Meanwhile, real-time dynamic detection can effectively indicate the effect of immunotherapy to avoid over-treatment.

Figure 1 The cohort of non-metastatic dMMR colorectal cancer with PD-1 treatment.
(A) Schematic diagram of detecting dynamic serum protein expression in dMMR colorectal cancer with PD-1 treatment; (B) Endoscopic and MRI/CT images were shown in Early-cCR (clinical or pathological Complete Response with 4 cycles of immunotherapy), Late-cCR (clinical or pathological Complete Response with over 4 cycles of immunotherapy), and Non-cCR groups; (C) A Total of 21 non-metastatic dMMR colorectal cancer patients with PD-1 treatment have 11 patients with Early-cCR, 4 patients with Late-cCR, and 6 patients with non-cCR. Clinical features of dMMR colorectal cancer with PD-1 treatment (Table 1).
Figure 2 Olink proteomics analysis in serum proteins of non-metastatic dMMR colorectal cancer with PD-1 treatment.
(A) Volcano plot showed that serum protein variation between pre-treatment and post-treatment; (B) Decreasing expression of serum proteins in the process of PD-1 treatment; (C) Increasing expression of serum proteins in the process of PD-1 treatment; (D) Cluster analysis of serum proteins was shown in pre-treatment and post-treatment; (E) Heat map showed the difference of serum proteins between cCR group and non-cCR group; (F) Top 5 potential marker proteins in each cCR group and non-cCR group were analyzed by ROC curve.