Study of a custom panel of CXC chemokines in the serum from metastatic CRC patients as predictive and/or prognostic biomarkers

Abstract

[eng] Worldwide, CRC is the third most common cancer considering both sexes and represents the second most common cause of cancer-related death. CRC patients’ survival is related to the tumor stage at the time of diagnosis. While treatment options rapidly increase for other types of cancer, only a few advances have been made in the treatment of CRC in the last decades. In the advanced disease, first-line treatment is based on the combination of chemotherapy (a fluoropyrimidine with oxaliplatin or irinotecan) plus an anti-EGFR antibody (cetuximab or panitumumab only in RAS WT patients) or an antiangiogenic drug (Beva). In this setting, 5-year survival rates are less than 10%, being chemotherapy resistance the main reason for disease progression. Therefore, finding useful and reliable predictive and prognostic biomarkers, along with druggable targets is necessary, to optimize the efficacy of current and upcoming treatments. It has been proposed that serum levels of certain chemokines may be used as predictive markers of response to chemotherapy. CXC chemokines are a family of small cytokines (8 to 10 kDa), that signal through G-protein-coupled receptors, CXCRs. Secreted by tumor cells, leukocytes, fibroblasts, endothelial and epithelial cells, they chemoattract several cell types such as neutrophils and lymphocytes, fibroblasts, and eosinophils. All these cell populations have diverse effects on tumor progression, depending on which are being attracted to the tumor microenvironment by the CXC chemokines. Additionally, in CRC we reported that CRC cell lines with acquired resistance to oxaliplatin overexpressed and secreted high amounts of some CXC chemokines including CXCL1, CXCL2, and CXCL8, because of an acquired hyperactivation of the NF-κB pathway. Hence, considering these results, together with the fact that CXC chemokines are secreted, and therefore can be easily detected in the blood of patients, we studied a panel of 11 CXC chemokines in metastatic CRC patients’ serum treated with OXA-based schedules as first-line treatment. To test our hypothesis we collected serial blood samples: at baseline, at response to treatment evaluation (after 3 months of treatment) and at time of progression/end of the study. We analyzed the samples by a Luminex-based analysis, which has proven to be a feasible and suitable technique. In the case of one of the chemokines, CXCL13, we found a strong correlation between values obtained by Luminex and ELISA. In general terms, all studied chemokines followed a pattern of increase-decrease along the treatment, with increasing values at the time of response evaluation, especially in the case of angiogenic chemokines. Additionally, with some exceptions, at baseline time-point, angiogenic chemokines are more abundant in mCRC patients’ serum than the angiostatic ones. Interestingly, most of these angiogenic chemokines are significantly associated with clinicopathological characteristics related to the number of metastasis and the metastatic site. Among all chemokines studied, only CXCL2 is associated with response to treatment. Specifically, increased levels of CXCL2 at baseline predicted a worse response to OXA-based first-line chemotherapy. Nevertheless, the predictive value of CXCL2 should be further validated. Moreover, CXCL13 appears to be an independent factor of prognosis in mCRC patients treated with first-line OXA-based schedules as follows: ‒ On one hand, low pre-treatment CXCL13 serum levels predict better OS and PFS, which may be related with the fact that levels of CXCL13 are higher in patients than in healthy controls. ‒ On the other hand, an increase of CXCL13 at the time of response evaluation predicts better OS and PFS; those patients with low basal CXCL13 and an increase in its levels at the time of response evaluation are indeed the ones with the best prognostic. Our results were confirmed in part in a similar independent cohort of CRC patients. According to the results of the in silico analysis in liver metastasis samples from CRC patients, increased levels of CXCL13 after treatment with OXA-containing schedules may be indicative of a long-term induced immune response, as CXCL13 expression correlates with a more immunogenic TME as well as with the presence of TLSs. Both CXCL13 expression and TLSs-associated signatures are associated with better prognosis in the studied cohort. In summary, we have demonstrated that the serum levels of most of the CXC here studied are altered along the OXA-based first-line treatment in mCRC patients and that specifically, CXCL2 and CXCL13 may be useful predictive and prognostic biomarkers in this setting. Nevertheless, these results may be further validated in larger cohorts of patients.