Lung cancer is the leading cause of cancer-related death worldwide. The two main forms of lung cancer are non-small cell lung cancer (NSCLC) (accounting for approximately 85% of all lung cancers) and small cell lung cancer (approximately 15%). Although progress has been made in early detection and standard treatment, non-small cell lung cancer is often diagnosed at an advanced stage and has a poor prognosis. The treatment and prevention of lung cancer are major unmet needs, and a low-risk, efficient, and targeted treatment method is urgently needed [
71]. Engineered MSC-exos can serve as effective biological carriers that exert regulatory effects on the malignant behaviours of lung cancer cells, including proliferation, migration, invasion, and metastasis. Studies have shown that in NSCLC cell models and animal models, engineered MSC-derived exo-mediated miR-631 delivery could control NSCLC malignant behaviours by regulating the transcription factor 2/phosphatidylinositol 3-kinase/Akt signalling pathway [
72]. Engineered MSC-exos transport and deliver miR-204 to act on NSCLC cells, and the overexpression of miR-204 inhibits KLF7 expression and AKT/HIF-1α pathway activity, thereby inhibiting NSCLC migration and invasion [
73]. Bone marrow-derived MSCs (BMSCs) can produce miR-126-3p to target and inhibit CCR1 expression, thereby inhibiting neural cadherin (N-cadherin, N-cad) and vimentin expression, promoting epithelial cadherin (E-cadherin, E-cad) expression, and ultimately inhibiting the proliferation, migration, and invasion of A549 lung cancer cells [
74]. Engineered MSC-exos can also transport and deliver negative regulatory factors, intensifying the malignancy of tumours. Studies have shown that human bone marrow-derived MSC-exos (BMSC-exos) can deliver miR-425 into lung cancer cells, inhibit CPEB1 expression, and promote lung cancer cell proliferation, invasion, and metastasis [
75]. Furthermore, studies have shown that human BMSC-exos can mediate E2F2 expression by delivering miR-631 to NSCLC cells to regulate NSCLC malignant behaviours [
76]. Considering the relationship between malignant lung cancer behaviours and their internal death outcomes, engineered MSCs may be a treatment that promotes programmed death in tumour cells, but their safety and effectiveness still need to be considered. Engineered MSC-exos can also exert various effects depending on their preculture conditions. Studies have shown that unstimulated human bone marrow-derived MSC-exos carrying miR-21-5p act on A549 and H23 lung cancer cells, downregulating PTEN, PDCD4, and RECK gene expression and promoting proliferation, survival, invasion, EMT, and macrophage M2 polarization. Notably, after hypoxic pretreatment, the effects of engineered MSC-exos were more significant [
77].