The Perturbation of Tumour Microenvironment in Pancreatic Ductal Adenocarcinoma in Response to the Chemoradiotherapy: Insights from single-cell RNA sequencing Analysis with Focus on Lymphoid Lineage

Pancreatic ductal adenocarcinoma (PDAC) accounts for more than ۹۰ percent of pancreatic tumors. The GLOBOCAN survey in ۲۰۲۲ announced PDAC as the sixth cause of cancer death globally. This cancer is usually diagnosed in advanced stages with a wide spectrum of symptoms such as epigastric abdominal pain, weight loss, appetite alterations, etc. The best possible combination therapy for PDAC is surgical resection besides adjuvant chemotherapy with FOLFIRINOX (folinic acid [leucovorin], fluorouracil [۵-FU], irinotecan and oxaliplatin), with or without radiation; but unfortunately, the ۵-year overall survival (OS) after undergoing such treatments is still ۳۰ to ۵۰%. Methods: To begin, a raw single-cell single-cell RNA sequencing dataset consisting of ۴۳ primary PDAC tumor samples that either were treatment-naïve or received neoadjuvant therapy with different therapeutic regimens was obtained from the NCBI database using the code GSE۲۰۲۰۵۱. On Python, the Scanpy toolkit was leveraged for data analysis. Initially, data from the quality control phase were removed to remove dead cells, dividing cells, and stressed cells. Then, the normalization performed through scanpy, and batch effect on the samples was then removed with the harmony package.Finally using the Squidpy algorithm, we discovered the specific ligand-receptor interactions between different cells. The Bonferroni formula was used to calculate the Adjusted P-value. Results: We categorized approximately ۲۲۵,۰۰۰ cells into different groups based on the treatment regimens and their response (poor, minimal, and moderate). Our analysis showed the rise in the fraction of lymphoid cells, cancer-associated fibroblasts (CAFs) and pericytes in the treated samples. The compression between moderate response and untreated cells increased the fraction of CD۴+ and functional CD۸+ T lymphocytes, while the population of dysfunctional CD۸+ T cells and natural killers decreased. In the untreated group, the most frequent interactions among lymphoid cells were between CD۸+ T cells, natural killer cells, and regulatory T cells. In the treated cells that had a moderate response to the therapy, the most interactions were between Natural Killer cells and CD۴+ T cells. We also looked at the expression of the inhibitory immune checkpoint (IIC) panel. The untreated group had high levels of ENTPD۱, HAVCER۲, LY۹, and TIGIT, while the poor, minimal, and moderate response groups had low levels of each. Interestingly, the expression of PRF۱, a cytotoxic gene, had increased in the treatment group. Finally, all of the treatment groups' response statuses showed enhanced Estrogen signaling. Conclusion: Considering the significant roles of lymphoid cells in the tumor microenvironment, we decided to investigate their behavior in PDAC TME, both with and without treatment. As expected, the treatment increased the fraction of this lineage. When lymphoid cells in PDAC TME interacted with each other, we saw a change between not being treated and having a moderate response to treatment, which led to the activation of anti-tumor functions in a good way. We also observed an increase in the expression of pathways that can improve anti-tumor immunity, e.g., cytolysis by NK cells. These findings shed light on the cellular and molecular mechanisms in PDAC TME and after treatment, suggesting novel targets for therapeutic strategies.

کلیدواژه ها:

Chemoradiotherapy ، Lymphoid cells ، Pancreatic ductal adenocarcinoma