Both primary and secondary resistance to antineoplastic treatments remains a major challenge in colorectal cancer (CRC). This underscores the urgent need to develop tools that can predict and assess the response to antitumor therapies. Fascin, a protein involved in tumour invasion and metastasis, has recently been identified for its role in resistance to chemotherapy and immune checkpoint inhibitors, such as anti-PD1 in breast cancer. Given this, our group has extensive experience in characterizing fascin in CRC and discovering new drugs with anti-fascin activity. The main aim of this work is to evaluate the effectiveness of anti-fascin compounds in reversing oxaliplatin chemoresistance in in vitro CRC models.

Eight colorectal cancer cell lines were used, four sensitive to oxaliplatin (HT29, LoVo, DLD1 and LS513) and four resistant derivatives of the former (HTOXAR, LoVOXAR, DLDOXAR and LSOXAR). These were cultured according to ATCC recommendations, under standard incubation conditions at 37°C with 5% CO₂. The cells were treated with oxaliplatin and fascin inhibitors (Imipramine and NP-G2-044), in monotherapy and in combination. Cell viability was assessed using the colorimetric XTT assay. Fascin levels in these lines were obtained from microarray data available in the GEO database, specifically from the GSE30011 study, and immunohistochemistry (IHC).

In resistant cell lines, a higher IC50 for oxaliplatin was confirmed comparatively to the sensitive lines, indicating a resistance to the drug. The anti-fascin compounds NP-G2-044 and imipramine, in monotherapy, reduced cell viability in all lines, with NP-G2-044 being the most effective. The combination of NP-G2-044 or imipramine with oxaliplatin significantly decreased viability in HTOXAR and DLDOXAR (up to 40% and 30%, respectively). In LoVOXAR, only the combination with NP-G2-044 was effective, reducing viability by 30%, suggesting a synergistic effect capable of reversing oxaliplatin resistance. However, in LSOXAR, the tested combinations did not improve the response to oxaliplatin. FSCN1 expression increased with oxaliplatin resistance in all the lines, except for LSOXAR, being notable in HTOXAR and DLDOXAR, which could explain the high efficacy of the combination treatments in the latter cell lines. IHC analysis further validated these results, confirming fascin’s differential levels related to oxaliplatin resistance.

Our findings highlight the key role of fascin in oxaliplatin resistance in CRC. Although the anti-fascin compounds NP-G2-044 and imipramine in monotherapy could be viable therapeutic options, higher concentrations would be required to achieve inhibitory effects comparable to oxaliplatin in resistant cells. However, the combination of fascin inhibitors with oxaliplatin exhibited a great ability to reverse drug resistance, showing promising therapeutic potential to overcome chemoresistance.