Novel candidate factors predicting the effect of S-1 adjuvant chemotherapy of pancreatic cancer

Abstract

The collagen gel droplet-embedded drug sensitivity test (CD-DST) was revealed to be useful for predicting the effect of S-1 adjuvant chemotherapy for pancreatic ductal adenocarcinoma (PDAC). However, collection of an adequate number of PDAC cells is difficult due to the surrounding fibroblasts. Thus, the aim of this study was to discover novel biomarkers to predict chemosensitivity based on the CD-DST results. Proteomics analysis was performed using liquid chromatography tandem mass spectrometry (LC-MS/MS). Candidate proteins were validated in patients with 5-FU CD-DST results via immunohistochemistry (IHC). The relationships between the candidate proteins and the effect of the adjuvant S-1 were investigated via IHC. Among the 2696 proteins extracted by LC-MS/MS, C1TC and SAHH could accurately predict the CD-DST results. Recurrence-free survival (RFS) was significantly improved in the IHC-positive group compared with the IHC-negative group in both factors. The negative group did not show a significant difference from the group that did not receive S-1. The double-positive group was associated with significantly prolonged RFS compared to the no adjuvant chemotherapy group. C1TC and SAHH have been shown to be useful biomarkers for predicting 5-FU sensitivity as a substitute for the CD-DST in adjuvant chemotherapy for PDAC.

Figure 1

Volcano plot of detection protein created by Perseus. The difference in the intensity of each protein between the HS group and the LS group was calculated by Perseus, and significant difference was evaluated by Student's t-test to prepare a Volcano plot. The analysis was performed with fold change > 0.1 and FDR = 0.05. HS high sensitivity, LS low sensitivity.

Figure 2

Recurrence free survival of patients with expressing each candidate factors and no adjuvant chemotherapy. In both C1TC and SAHH, a significant improvement of RFS was observed in the positive group compared to the negative group. Furthermore, positive group showed significant improvement of RFS compared with no adjuvant chemotherapy group. On the other hands, no significant difference was fond between negative group and no adjuvant group in both C1TC and SAHH.

Figure 3

Recurrence free survival after combining C1TC and SAHH. There were 23 cases of both C1TC and SAHH showed positive expression, 8 cases showed both negative expressions, 8 cases showed only SAHH positive and 8 cases of C1TC positive respectively. Double positive group showed a significant improvement of RFS compared to No adjuvant group. On the other hands, when C1TC and/or SAHH was negative, there was no significant difference compared with no adjuvant group. When C1TC and/or SAHH negative cases was combined into one group and compared with double positive or No adjuvant group, RFS was dramatically worse compared with double positive group and almost similar with No adjuvant group.

Figure 4

Study design. The cohort of Step1 was targeting the patients evident the results of CD-DST. The cohort of Step2 is targeting the PDAC patients with S-1 adjuvant chemotherapy. We set no adjuvant patients group as control cohort of this study. CD-DST collagen gel droplet embedded drug sensitivity test, PDAC pancreatic ductal adenocarcinoma.

Figure 5

Immunoreactive score (IRS). The Immunoreactivity scoring system (IRS), which is a combination of the intensity (1 to 4 points) and proportion of positive cells, was used. 8 points and more were judged to be IRS positive. Scale bar: 100 μm.