NF-κB Inhibition Mitigates Colorectal Cancer Lung Metastasis

Abstract ID 131069 Poster Board 256 Globally, colorectal cancer (CRC) stands as the third-leading cause of cancer-related mortality, impacting over 1.85 million individuals and resulting in more than 850,000 deaths annually. Alarmingly, at the time of diagnosis, 20% of patients present with metastatic cancer, while 25% of those initially diagnosed with localized disease eventually develop metastases. Lung metastases afflict 15% of metastatic CRC (mCRC) patients, with the lung emerging as the second most common site of metastasis occurrence, following the liver. The constitutive activation of canonical NF-κB has been observed in at least 40% of CRC tissues, promoting tumor cell proliferation and chemo-resistance. Here, we hypothesized that NF-κB inhibition could mitigate CRC lung metastases. CT26-Luc cells, mouse colorectal tumor cells with KRASG12D mutation and stably transfected with Luciferase, were intravenously injected into 5-week-old BALB/cJ mice at a dose of 1x10⁵ cells per mouse. Seven days after tumor cell injection, the mice were randomly divided into two treatment groups: control and p5RHH-p65 siRNA nanoparticles at dose of p65 siRNA of 0.5 mg/kg (Rx). The treatments were administrated three times a week for two weeks. On each treatment day, mice were injected with D-Luciferin, potassium salt at a dose of 150 mg/kg for IVIS imaging. The quantification of IVIS imaging results (Fig. A) suggested that the treatment significantly reduced the burden of lung metastasis as confirmed by H&E staining (Fig. B-C). The mice were euthanized 72 hours after the last treatment dose. Blood was collected via cardiac puncture, and safety of the treatment was validated by normal blood chemistries. Moreover, the treatment did not suppress innate and adaptive immune responses, as evidenced by the number and composition of splenocytes, as well as the T-cell responses to stimulations. Since tumoral CD8+ infiltration is correlated with favorable CRC prognosis, we evaluated CD8+ T cell infiltration by immunofluorescence staining. The results showed that canonical NF-κB inhibition promoted CD8+ T cell infiltration (Fig. D (Ctrl)-E (Rx)). Moreover, cell proliferation, as indicated by Ki67 staining showed that the treatment inhibited tumoral proliferation (Fig. F(Ctrl)-G(Rx)). In conclusion, NF-κB inhibition by p65 selective siRNA nanoparticles could be further investigated for mitigating lung metastases in mCRC patients. The work is supported by NIH, R21HL154009.