By Ana Espino | Published on March 10, 2026 | 3 min readColorectal cancer (CRC) remains one
of the leading causes of cancer-related mortality worldwide, despite major
advances in surgery, chemotherapy, and targeted therapies. Improvements in
diagnostic strategies and the introduction of modern therapeutic combinations
have increased survival, particularly in metastatic disease. However, these
gains are undermined by the almost inevitable emergence of therapeutic
resistance, which leads to relapse and tumor progression.
Standard treatment protocols combine
cytotoxic agents such as 5-fluorouracil, oxaliplatin, and irinotecan with
targeted therapies directed against EGFR or VEGF. More recently, immunotherapy
has shown efficacy in subgroups of patients with high microsatellite
instability. Nevertheless, a significant proportion of patients exhibit primary
resistance, while others develop acquired resistance after an initial response.
This resistance does not arise from
a single mechanism but from a complex interaction between genetic alterations,
tumor plasticity, the immune microenvironment, and therapeutic pressure.
Understanding these mechanisms has become essential for optimizing treatment
personalization and extending survival.
This review, published in 2025 in
the International Journal of Molecular Sciences, provides an in-depth
analysis of the molecular and cellular mechanisms involved in therapeutic
resistance in CRC, as well as innovative strategies aimed at preventing or
overcoming it.
How does the tumor evade treatment?
This review summarizes the
mechanisms underlying resistance to chemotherapy, targeted therapies, and
immunotherapy.
At the molecular level, mutations in
KRAS, NRAS, or BRAF alter the response to EGFR inhibitors. Constitutive
activation of the MAPK and PI3K/AKT pathways promotes cellular
proliferation independent of therapeutic signals. Alterations in the TP53
gene reduce apoptosis induction following exposure to cytotoxic agents.
Resistance to oxaliplatin and
irinotecan involves enhanced DNA repair mechanisms, overexpression of
efflux transporters such as P-glycoprotein, and metabolic reprogramming.
Cancer stem cells also contribute to clonal persistence following
treatment.
The tumor microenvironment
plays a crucial role. Hypoxia, chronic inflammation, and interactions with
cancer-associated fibroblasts promote tumor cell survival. In addition,
resistance to immunotherapy is often linked to microsatellite stability
(MSS), which limits the effectiveness of immune checkpoint inhibitors.
The authors describe several
strategies to overcome these resistances. These include therapeutic
combinations targeting multiple signaling pathways simultaneously, BRAF
inhibitors combined with anti-EGFR agents, modulation of the tumor
microenvironment, and the development of predictive biomarkers to
personalize treatment.
Anticipating resistance to improve
treatment
Therapeutic resistance represents
one of the major barriers to durable survival improvement in colorectal cancer.
This review aimed to decipher the
underlying biological mechanisms and identify strategies to overcome them. The
data indicate that resistance results from complex interactions between genetic
alterations, tumor plasticity, and the tumor microenvironment, highlighting the
need for a multidimensional approach.
Current limitations include
significant inter- and intra-tumor heterogeneity, which makes it
difficult to accurately predict resistance mechanisms. Moreover, the clinical
validation of combination strategies requires robust prospective trials.
In the long term, integrating molecular
biomarkers, multi-omics analyses, and adaptive therapeutic strategies may
allow clinicians to anticipate and overcome resistance, paving the way for a
more personalized and dynamic approach to colorectal cancer treatment.
Read next: Colorectal cancer: a hidden intestinal virus may double the risk
About the author – Ana Espino
PhD in Immunology, specialized in Virology
As a scientific writer, Ana is passionate about bridging the gap between research and real-world impact. With expertise in immunology, virology, oncology, and clinical studies, she makes complex science clear and accessible. Her mission: to accelerate knowledge sharing and empower evidence-based decisions through impactful communication.
