Abstract Body: Cancer therapies can impair vascular function by activating the renin-angiotensin system (RAS), leading to endothelial senescence and disrupted angiogenesis. Angiotensin II (Ang-II) is a key driver of this dysfunction, while RAS inhibitors and Angiotensin-(1–7) (Ang-1-7) are under investigation for their protective potential. In parallel, epigenetic mechanisms, particularly those involving long noncoding RNAs (lncRNAs), are critical in regulating endothelial responses. Our lab identified the Ang-II-dependent long non-coding RNA CASC15, which has over 300 isoforms. However, its role in endothelial biology and interaction with RAS remains unclear.
To understand the effects of RAS dysregulation on CASC15, we profiled isoform expression in human umbilical vein endothelial cells (HUVECs) and found isoforms CASC15-202 and CASC15-206 significantly downregulated by Ang-II; with Ang-1-7 co-treatment restoring their levels (n=5, p<0.05).
To assess the functional role of these isoforms, we performed knockdown (KD) experiments targeting CASC15-202, CASC15-206, and a pan-isoform KD approach in HUVECs. CASC15-202 KD increased senescence by 71% compared to CT (0.12 vs. 0.07; n=3, p=0.0366), while CASC15-206 showed a 51% increase under doxorubicin compared to CT (0.29 vs. 0.19; n=3, p<0.0001).
We further assessed DNA damage via γH2AX foci. CASC15 KD increased γH2AX under basal conditions over 200% compared to CT, including CASC15-202 (0.30 vs. 0.13; n=3, p=0.0311) and CASC15-206 (0.36 vs. 0.13; n=3, p=0.0034). Ang-II further amplified γH2AX in CASC15-202 by 44% (0.65 vs. 0.45; n=3, p=0.0093), where Ang-1-7 reduced damage across all KD, including CASC15-202, by 60% (0.12 vs. 0.30; n=3, p=0.0232).
To assess the role of CASC15 in angiogenesis, we evaluated tube formation capacity. CASC15-202 KD showed impairment in all angiogenic parameters, by reducing mesh area by 50% (0.004 vs. 0.008 µm²; n=3, p=0.0006), and number of branches by 85% (0.06 vs. 0.41 µm; n=3, p=0.0029) compared to CT.
Our study reveals that CASC15 isoforms, particularly 202, play a key role in endothelial stress responses and vascular homeostasis, with Ang-1-7 acting as a protective agent against stress-induced dysfunction. Future research should focus on the specific mechanisms by which CASC15 isoforms regulate endothelial function and explore the therapeutic potential of Ang-1-7 in mitigating cancer-treatment-related vascular toxicity.