In tumor RT, the phenomenon where radiation causes oxidative stress and DNA damage in nearby unirradiated cells or tissues is known as the radiation-induced bystander effect (RIBE). Recent studies have shown that certain components of irradiated tumor cells, such as cell membranes, cell secretions, and microparticles (RT-MPs) released by these cells, possess significant antitumor capabilities and may play a crucial role in RIBE [
120,
121]. Wan et al
. discovered that RT-MPs have the ability to kill tumor cells and reprogram the immune microenvironment. When RT-MPs are injected externally, they effectively induce ferroptosis in tumor cells and trigger ICD, which in turn activates the host immune response. Additionally, when TAMs engulf RT-MPs, they undergo a polarization from M2 type to M1 type, thereby reactivating their antitumor function. An interesting observation is that TAMs treated with RT-MPs express higher levels of PD-L1, which enhances the sensitivity of tumors to immunotherapy and demonstrates the potential of combining RT and immunotherapy. The induction of a broad immune response by RT-MPs, along with their promotion of RIBE, holds great significance in combating drug-resistant tumors and inhibiting tumor metastasis and recurrence [
122,
123]. Analysis using electron microscopy has revealed the vesicle structure of RT-MPs at the nanoscale, further showcasing their potential as a form of nanomedicine and for use in nanodrug delivery systems. Deng et al
. utilized the potential of RT-MPs to induce ferroptosis and act as biocompatible carriers to develop a tumor nanodrug delivery system. To enhance the antitumor effect, they loaded the ferroptosis inducer RSL-3 into RT-MPs, which activated the cGAS–STING pathway and promoted the polarization of TAMs from M2 to M1. Additionally, they incorporated the mitochondria-targeting peptide CT20p into RT-MPs, leading to increased production of ROS and lipid hydrogen peroxide. This alteration changed the mitochondrial membrane potential, intensified ferroptosis, and synergistically exerted antitumor effects [
124]. To further enhance targeting and regulation of the TME, Lu et al
. genetically engineered RT-MPs and applied them to combat brain metastases (BRM) of lung cancer. They transfected tumor cells with lentiviral vector plasmids to enable RT-MPs to express a scavenging receptor B1 (SR-B1) targeting peptide. SR-B1 is expressed on the surface of blood–brain barrier endothelial cells, microglia, and Lewis lung cancer (LLC) cells. As a result, it effectively improves blood–brain barrier permeability and targets BRM cells and tumor-related M2 microglia. The nanomedicine also carries a ubiquitin-specific protease 7 (USP7) inhibitor, which activates the mitogen-activated protein kinase (MAPK) signaling pathway, effectively reprograms M2 microglia, improves ITM, and works in conjunction with RT-MPs to directly and indirectly inhibit BRM [
125,
126]. In addition to nanodrug delivery systems, irradiated tumor cell products are also used in the construction of tumor vaccines. Tuo et al
. utilized irradiated tumor cell membranes to wrap polylactic-glycolic acid (PLGA) NPs, thereby creating a tumor vaccine that enhances host immunity. This particular type of irradiated tumor cell membrane expresses a higher level of major histocompatibility complex I (MHC-I) and contains more damage-associated molecular patterns (DAMPs), resulting in stronger immunogenicity. The biomimetic NP is loaded with a TLR7 agonist (R837), which effectively accumulates in lymph nodes and activates DCs, thereby inducing antitumor immune responses [
127,
128]. In summary, the use of irradiated tumor cell components to prevent or treat tumors by simulating the occurrence of RIBE is a promising strategy for indirect RT. This approach demonstrates effective tumor eradication and immune activation capabilities.