Nk cells as biomarkers of response to antiegfr therapy in metastatic colorectal cancer: clinical implications and therapeutic opportunities
- Autores: Carmen Luz Navarrete S
- Directores de la Tesis: Enrique Aranda Aguilar (dir. tes.), Antonio Rodríguez Ariza (dir. tes.)
- Lectura: En la Universidad de Córdoba (ESP) ( España ) en 2026
- Idioma: inglés
- Tribunal Calificador de la Tesis: María Teresa Roldan Arjona (presid.), Erika Martineli (secret.), Jesús García-Foncillas López (voc.)
- Programa de doctorado: Programa Oficial de Doctorado en Biomedicina
- Materias:
- Enlaces
- Tesis en acceso abierto en: Helvia
- Resumen
Colorectal cancer (CRC) is the third most commonly diagnosed cancer and the second leading cause of cancer-related death worldwide, with its incidence expected to exceed 3 million new cases by 2040. In metastatic colorectal cancer (mCRC), therapeutic advances have improved survival outcomes, and cetuximab, an anti-EGFR monoclonal antibody, remains a key treatment for RAS wild-type (RASwt) and EGFR-expressing tumours. However, up to 65% of RASwt mCRC patients derive limited or no benefit from cetuximab, highlighting the need to explore resistance mechanisms beyond classical molecular alterations, particularly those involving immune-mediated responses. Cetuximab can induce antibody-dependent cell-mediated cytotoxicity (ADCC) through the interaction of its Fc region with the CD16 receptor on natural killer (NK) cells, leading to tumour cell lysis. Therefore, the balance and functional status of NK cell subsets may critically determine cetuximab efficacy.
To investigate this hypothesis, blood samples from mCRC patients were collected both before first-line cetuximab therapy and at disease progression. Patients were classified as non-responders (NR, n=14) if progression occurred within nine months, or responders (R, n=17) if progression occurred after nine months or had not yet occurred. Although no major clinicopathological differences were observed between groups, survival analysis confirmed significantly poorer outcomes among NR patients.
Analysis of circulating immune mediators in baseline plasma samples revealed that NR patients displayed elevated pro-inflammatory cytokines, suggesting a dysfunctional immune environment that could impair effective ADCC. Conversely, R patients exhibited upregulation of immune mediators linked to coordinated antitumour responses. Proteomic profiling of isolated NK cells showed distinct expression patterns between NR and R groups, with alterations in critical pathways such as TGFβ and PPAR signalling. These pathways hinder the transition from CD56 Bright (regulatory) to CD56 Dim (cytotoxic) NK cells, thereby reducing their cytolytic potential.
Flow cytometric immunophenotyping confirmed that NR patients had a higher proportion of non-cytotoxic NK cells (Bright and Dim CD16⁻), along with increased expression of CD57 and TIGIT and reduced levels of activating markers. This indicates a senescent or exhausted NK phenotype, which may underlie the lack of response to cetuximab. Based on these data, a predictive immunophenotypic score was developed, integrating key NK cell markers (non-cytotoxic NK cell percentage, NKG2A, NKp46, and/or TIGIT). Patients with more than three positive parameters had significantly worse overall survival and time to progression, supporting the predictive value of this signature.
Comparing baseline and progression samples revealed further insights into resistance mechanisms. In NR patients, disease progression was associated with upregulation of TGFβ signalling and reduced NK cytotoxicity. In R patients, progression involved dysregulation of apical junction pathways, potentially impairing immunological synapse formation between NK and tumour cells, along with decreased CD16 expression, which could compromise ADCC and facilitate immune escape.
Two inhibitory receptors, NKG2A and TIGIT, emerged as potential therapeutic targets. Blocking NKG2A with monalizumab enhanced cetuximab-mediated ADCC in short-term assays; however, long-term experiments showed limited synergy, as cetuximab itself downregulated HLA-E, the ligand for NKG2A. In contrast, TIGIT blockade with tiragolumab significantly enhanced cetuximab-induced ADCC, particularly through Bright NK cells in 3D co-culture models. This suggests that NR patients with high TIGIT expression might achieve substantial clinical benefit from combined cetuximab and anti-TIGIT therapy.
In summary, this study demonstrates that NK cell dysfunction, characterised by imbalanced subset distribution, senescent phenotypes, and overexpression of inhibitory receptors, plays a key role in cetuximab resistance in mCRC. The identification of inhibitory receptors such as TIGIT and NKG2A on NK cells highlights promising immunotherapeutic opportunities. Notably, TIGIT blockade effectively restores NK cell cytotoxicity and enhances cetuximab efficacy. These findings underscore the importance of incorporating NK cell profiling into predictive models of cetuximab response and support the clinical evaluation of anti-TIGIT therapies to overcome resistance in metastatic colorectal.
