Biology subjects

Velasquez, B.

Publications and source records attributed to Velasquez, B..

4 recordsLinked to original sources

bioRxiv2025

FLASH Radiotherapy Mitigates Radiation-Induced Lymphopenia and Prevents Immunosuppression via Chk1-STAT3 Axis Modulation in a Preclinical Thoracic Irradiation Model

Background and AimsRadiation-induced lymphopenia (RIL) is a frequent side effect of conventional radiation therapy (CONV RT), due to the high radiosensitivity of circulating lymphocytes. Ultra-high dose rate "FLASH" RT may preferentially spare normal tissue while maintaining tumor control. This study evaluates the impact of single-fraction and multi-fraction thoracic FLASH RT on lymphocyte preservation, apoptosis, and immunosuppressive signaling in mice. MethodsWe compared the immunological impact of thoracic FLASH RT and CONV RT in C57BL/6 mice using single-fraction (17 Gy) and multi-fraction (2 Gy x 5) regimens using the Mobetron (IntraOp). Longitudinal blood sampling was performed at multiple time-points post-irradiation through facial vein bleed with flow cytometry analysis for CD4+, CD8+, CD19+, and NK cells to assess lymphocyte counts, apoptotic lymphocytes through Annexin V staining, and immune suppression by examining regulatory T cells (Tregs) and PD-1/PD-L1 expression. Mechanistic studies included immunofluorescence and Western blot analyses of splenic tissues to evaluate Chk1 and STAT3 signaling pathways. ResultsIn single-fraction RT, FLASH significantly reduced lung and heart fibrosis (p < 0.0001) at 28 weeks post-RT. The FLASH effect was also seen acutely on circulating immune cells, with significantly reduced lymphocyte apoptosis and accelerated recovery of CD4, CD8, CD3, NK, and B cell populations compared to CONV RT in both single-fraction and multi-fraction regimens. Conversely, CONV RT induced long-lasting increases in Tregs and sustained PD-1 and PD-L1 expression on T- and B-cells at 2- and 5-months post-irradiation in both fractionation regimens. Within the spleen, we also found CONV RT induced sustained activation of the Chk1-STAT3 pathway in CD45+ immune cells, which correlates with increased PD-1/PD-L1 expression. ConclusionFLASH RT mitigates RIL, reduces lymphocyte apoptosis, and prevents long-term immunosuppression by reduced activation of the Chk1-STAT3 pathway. These findings suggest FLASH RT may confer immunological advantages over CONV RT to enhance therapeutic efficacy.

cancer biology↗

bioRxiv2025

Harnessing drought tolerance in a reference set of Andean amaranths

Climate change and low-input farming systems increasingly expose crops to drought stress. Andean amaranths (Amaranthus spp.), as neglected and underutilized species, offer potential for climate-resilient agriculture due to their inherent drought tolerance and adaptability. In Northwest Argentina (NWA), a region with high environmental heterogeneity, exploiting this genetic diversity may improve food security. This study evaluated drought tolerance and yield stability among Andean amaranth genotypes to: assess the effects of genotype and GxE interaction, determine the potential for selecting specifically adapted genotypes, and identify high-yielding, stable genotypes for drought-prone conditions. Eleven genotypes (cultivars, breeding lines, and landraces of A. caudatus and A. mantegazzianus) were tested across four agroecological zones in NWA under irrigated and drought-stressed conditions. Grain yield data were analyzed using linear mixed models and AMMI analysis. Genotypes differed significantly in grain yield across environments and irrigation regimes. Strong GxE interactions led to genotype re-ranking across sites. Several A. caudatus breeding lines (G1, G2, G3, G6) combined high yield and stability. The A. mantegazzianus landrace (G11) was highly stable but low yielding. Amaranth genotypes showed distinct responses to drought, with some lines exhibiting broad adaptation and others, specific adaptation to stress-prone environments.

plant biology↗

bioRxiv2025

FLASH radiotherapy spares lymphocytes in tumor-draining lymph nodes and increases infiltration of immune cells in tumors

Radiotherapy (RT) delivered at conventional dose rates (CONV) can both stimulate antitumor immune responses and inhibit these immune responses by depleting circulating lymphocytes. Given the observed normal tissue sparing associated with ultra-high dose rate (FLASH) RT, we hypothesized that FLASH RT may protect lymphocytes while increasing the immunogenicity of cancer cells. We irradiated cancer cell lines in vitro with FLASH RT or CONV RT and assessed immunogenic mRNA and protein expression. Both HPV-positive cell lines MEER and TC-1 showed upregulation of Calr, Hmgb1, and cGAS-STING family members after FLASH RT but not after CONV RT in vitro. To assess changes in lymphocyte populations, we irradiated murine mEER tumors in syngeneic C57BL/6 mice with 27 Gy in 3 fractions of FLASH RT or CONV RT. In mice bearing FLASH irradiated tumors, tumor-draining lymph nodes contained greater numbers of CD8+ T cells (FLASH 1.7x104 vs 0.8x104 CONV; P<0.001) and CD4+ T cells (FLASH 2.3x104 vs CONV 1.2x104; P<0.001) after irradiation. FLASH RT was associated with increased numbers of activated CD44+CD62LloCD8+ and CD4+ lymphocytes. In irradiated tumors, FLASH RT was associated with increased CD8+ tumor-infiltrating lymphocytes, increased PD1 expression on these lymphocytes and increased PDL1 expression on macrophages. Compared with CONV RT, FLASH RT spared activated T cells in tumor-draining lymph nodes and in tumors but increased checkpoint inhibitor expression in tumors. These results suggest that FLASH RT may enhance antitumor immune responses by maintaining the immunogenic effects of RT while preserving lymphocyte numbers, which may be augmented with immune checkpoint blockade. SignificanceRadiation-induced lymphopenia is associated with poorer survival outcomes. New treatment approaches, like FLASH radiation therapy (FLASH RT), which reduce lymphopenia and enhance the antitumor response, could potentially lead to better outcomes for cancer patients.

cancer biology↗

bioRxiv2025

Mitochondrial Responses to Conventional and Ultra-high Dose Rate (FLASH) Radiation

PurposeUltra-high dose rate (>40 Gy/s, FLASH) radiation therapy (RT) provides equivalent tumor control while reducing normal tissue toxicity relative to conventional dose rate (CONV) RT. However, the mechanisms underlying the observed FLASH effect are unknown. We hypothesized that the preservation of mitochondrial integrity in nontumorigenic cells by FLASH RT could be a key factor in reducing normal tissue toxicity and improving overall treatment outcomes. MethodsWe examined mitochondrial health and function after CONV and FLASH in vitro, ex vivo, and in vivo through assays of metabolic flux, mitochondrial membrane potential, mitochondrial reactive oxygen species (ROS), mitochondrial DNA damage and copy number, mitochondrial morphology, and tumor growth and survival. ResultsIn in vitro assays, murine pancreatic cancer (PDAC) cells showed evidence of equal mitochondrial damage in response to CONV and FLASH, but nontumorigenic pancreatic cells were spared by FLASH. These results were recapitulated ex vivo, and mice treated with FLASH showed higher response rates and longer survival time than mice treated with CONV in an in vivo tumor model. ConclusionsCollectively, these results suggest that FLASH spares mitochondrial function in nontumorigenic cells, but not in PDAC cells, relative to CONV. The preservation of mitochondrial integrity in nontumorigenic cells may be a key mechanism underlying the reduced normal tissue toxicity observed with FLASH RT.

cancer biology↗