Small cell lung cancer stem cells display mesenchymal properties and exploit immune checkpoint pathways in activated cytotoxic T lymphocytes

Abstract

Small cell lung cancer (SCLC) is an aggressive tumor type with early dissemination and distant metastasis capacity. Even though optimal chemotherapy responses are observed initially in many patients, therapy resistance is almost inevitable. Accordingly, SCLC has been regarded as an archetype for cancer stem cell (CSC) dynamics. To determine the immune-modulatory influence of CSC in SCLC, this study focused on the characterization of CD44+CD90+ CSC-like subpopulations in SCLC. These cells displayed mesenchymal properties, differentiated into different lineages and further contributed to CD8+ cytotoxic T lymphocytes (CTL) responses. The interaction between CD44+CD90+ CSC-like cells and T cells led to the upregulation of checkpoint molecules PD-1, CTLA-4, TIM-3, and LAG3. In the patient-derived lymph nodes, CD44+ SCLC metastases were also observed with T cells expressing PD-1, TIM-3, or LAG3. Proliferation and IFN-γ expression capacity of TIM-3 and LAG3 co-expressing CTLs are adversely affected over long-time co-culture with CD44+CD90+ CSC-like cells. Moreover, especially through IFN-γ secreted by the T cells, the CSC-like SCLC cells highly expressed PD-L1 and PD-L2. Upon a second encounter with immune-experienced, IFN-γ-stimulated CSC-like SCLC cells, both cytotoxic and proliferation capacities of T cells were hampered. In conclusion, our data provide evidence for the superior potential of the SCLC cells with stem-like and mesenchymal properties to gain immune regulatory capacities and cope with cytotoxic T cell responses. With their high metastatic and immune-modulatory assets, the CSC subpopulation in SCLC may serve as a preferential target for checkpoint blockade immunotherapy .

Spatially resolved proteomic profiling identifies tumor cell CD44 as a biomarker associated with sensitivity to PD-1 axis blockade in advanced non-small-cell lung cancer

“…On the other hand, CD44 is a necessary protein for EMT, 5–9 and EMT has been associated with a broad inflammatory microenvironment characterized by coexistent upregulation of co-stimulatory and co-inhibitory checkpoint molecules in human lung cancer. 24 29–31 We also observed that intratumoral regions with elevated tumor cell CD44 had prominent upregulation of co-inhibitory (TIM-3, B7-H3, PD-L1) and co-stimulatory (ICOS, CD40, CD27) molecules in two independent NSCLC cohorts. Of note, although EMT has been generally associated with poorer outcomes and treatment resistance in several cancers, 6 7 some tumor types with more mesenchymal features such as sarcomatoid malignant pleural mesotheliomas 32 or certain subtypes of small cell lung cancers (SCLC), 33 also display an inflammatory microenvironment and show higher sensitivity to checkpoint blockade therapies.…”

“…It is a surface marker commonly overexpressed by tumor cells with cancer initiating properties, 6 7 20 and has therefore been repeatedly associated with cancer stem cells particularly in breast cancer. [20][21][22][23][24] To our knowledge, the association between tumor cell CD44 overexpression and improved clinical outcomes to PD-1 axis blockade has not been previously reported. In the present study, we have performed rigorous validation of this novel finding, including orthogonal biomarker assessment with a second QIF-based technology (with prior validation of an anti-CD44 antibody following recommended guidelines 16 ), and external validation utilizing whole tissue sections by independent investigators.…”

Pulmonary Neuroendocrine Neoplasms Overexpressing Epithelial-Mesenchymal Transition Mechanical Barriers Genes Lack Immune-Suppressive Response and Present an Increased Risk of Metastasis

“…Second, small cell lung carcinomas are associated with the lack of PD-L1 immunosuppressive barrier allowing the immune cell infiltration, but with high expression of desmosomes disassembly barrier, both facilitators of distant metastasis and shorter overall patient survival, otherwise be targeted effectively with immunotherapy PD-L1 expression. Third, the high levels of EMT transcriptions factors expressed by SCLC cells can confer mesenchymal properties, on the one hand justifying its histologic fusiform pattern, and on the other hand the acquisition of immune regulatory capacities for checkpoint blockade immunotherapy, as recently demonstrated in an elegant work made by Kursunel and colleagues (14).…”

“…For instance, normal lung contains a population of neuroendocrine cells (NE), referred as Kulchitsky cell, within the bronchial tree and neuroendocrine bodies in the periphery, which also might give rise to carcinoids, a specific group of tumors based on their secretory products, distinct staining characteristics, and ability to uptake and decarboxylate amine precursors (11). In contrast, SCLC do not arise from Kulchitzky cells, but from multipotent or undifferentiated neuroendocrine NE cells in the central bronchial tree (12)(13)(14) as previously demonstrated in experimental models genetically modified (15). Given these unusual characteristics of PNENs, not only is it still often difficult to oncologist predicts which tumors will invade, metastasize, and abbreviate the patient's life, nevertheless, effective adjuvant treatments still depend on identifying these tumors shortly after biopsy or surgery as well.…”

Tumor metastasis: Mechanistic insights and therapeutic interventions

“… 57 Compared with epithelial cancer cells, mesenchymal cancer cells are less responsive to anti‐cytotoxic lymphocyte‐associated protein 4 (CTLA4) immunotherapy. 59 In addition, the expressions of programmed death ligand‐1 (PD‐L1), PD‐L2, and B7 homolog 3 (B7‐H3) are up‐regulated in tumor cells that have undergone EMT, which can facilitate the immune escape of cancer cells. 58 , 60 …”