Oncología y Cáncer
PTEN status, tumor immune microenvironment, and survival in colorectal cancer
Figura representativa extraída de PubMed Central (PMC13477460)
Fuente oficial abierta: NCBI/PMC (PMC13477460)
PTEN Dysfunction, Tumor Immune Microenvironment Remodeling, and Sex-Dimorphic Survival Trajectories in Colorectal Cancer
Abstract
Phosphatase and Tensin Homolog (PTEN) loss is a pivotal driver of oncogenesis, metabolic reprogramming, and immunosuppression in colorectal cancer (CRC). Functional PTEN deficiency hyperactivates the phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling axis, driving uncontrolled cellular proliferation, evasion of apoptosis, and profound remodeling of the tumor immune microenvironment (TIME). Specifically, PTEN inactivation impairs anti-tumor immunity by suppressing cytotoxic CD8+ T-lymphocyte infiltration and facilitating the recruitment of immunosuppressive myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs). Crucially, emerging sex-and-gender-based analyses (SGBA) demonstrate that PTEN-driven immunomodulation operates through sex-dimorphic biological networks. Estrogen receptor-beta (ERβ) signaling, dynamic sex-steroid concentrations, and sex-biased epigenetic landscapes significantly modulate PTEN protein stability and baseline immune cell reactivity. Consequently, male and female CRC patients exhibit distinct clinico-pathological profiles and differential survival outcomes according to PTEN expression status. This review synthesizes the molecular mechanisms underpinning PTEN-deficient immune evasion, delineates sex-specific regulatory nodes in the PTEN/PI3K axis, and outlines targeted, sex-stratified therapeutic strategies designed to advance precision oncology in colorectal cancer.
Introduction & Cellular Mechanisms
Colorectal cancer (CRC) remains a leading cause of cancer-related mortality worldwide, characterized by marked genetic heterogeneity and variable responses to targeted and immune therapies. Among the driver molecular aberrations, loss of function or epigenetic silencing of the *PTEN* tumor suppressor gene represents a critical milestone in colorectal carcinogenesis. PTEN functions primarily as a lipid phosphatase that dephosphorylates phosphatidylinositol-3,4,5-trisphosphate ($\text{PIP}_3$) to phosphatidylinositol-4,5-bisphosphate ($\text{PIP}_2$), serving as the principal negative regulator of the canonical PI3K/AKT/mTOR signaling cascade.
```
[ Cell Membrane ]
Growth Factors / RTKs
│
▼
PI3K
│
├───( + )───► PIP3 ───► p-AKT ───► mTORC1 / Proliferation
│ ▲
[ PTEN ] ──────────┘ (Dephosphorylates PIP3 to PIP2)
(Inhibited by
Loss / Mutation)
│
▼ (PTEN Loss Consequences)
┌─────────────────────────┼─────────────────────────┐
▼ ▼ ▼
Lysosomal & Mitochondrial Immune Exclusion Suppressive Chemokines
Dysfunction (Autophagy↓) (CD8+ T Cells↓) (CCL2↑, CXCL12↑ -> MDSCs/Tregs↑)
```
At the cellular and organellar levels, loss of PTEN activity induces catastrophic signal transduction imbalances:
1. Hyperactivation of the PI3K/AKT/mTOR Axis: Loss of lipid phosphatase activity results in continuous $\text{PIP}_3$ accumulation at the plasma membrane, driving constitutive recruitment and phosphorylation of AKT at Thr308 and Ser473. Activated AKT downstream targets suppress glycogen synthase kinase 3 beta (GSK3β) and activate mTOR complex 1 (mTORC1), upregulating nutrient transport, protein synthesis, and glycolytic flux (the Warburg effect).
2. Organelle Dysfunction and Metabolic Stress: PTEN loss disrupts autophagy and mitochondrial quality control. Defective mitophagy accelerates the accumulation of damaged mitochondria, raising intracellular reactive oxygen species (ROS) levels and promoting genomic instability. Concurrently, altered lysosomal biogenesis secondary to hyperactive mTORC1 disrupts endo-lysosomal trafficking, suppressing normal antigen presentation pathways through major histocompatibility complex class I (MHC-I) molecules.
3. Tumor Immune Microenvironment (TIME) Exclusions: Functional PTEN deficiency remodels the secretory phenotype of CRC cells. Downstream activation of nuclear factor kappa B (NF-κB) and hypoxia-inducible factor 1-alpha (HIF-1α) increases the production of immunosuppressive cytokines (e.g., TGF-β, IL-10) and chemokines such as CCL2 and CXCL12. This altered secretome suppresses dendritic cell maturation, impairs CD8+ cytotoxic T-cell recruitment and activation (immune exclusion), and actively recruits immunosuppressive elements, including $\text{FOXP3}^+$ regulatory T cells (Tregs) and $\text{CD11b}^+\text{Gr-1}^+$ myeloid-derived suppressor cells (MDSCs). Furthermore, PTEN loss stabilizes programmed death-ligand 1 (PD-L1) expression via post-transcriptional mechanisms, reinforcing T-cell exhaustion within the tumor stroma.
Sex-Dimorphic Regulation & Translational Implications
Sex is a fundamental biological variable that influences CRC incidence, anatomical tumor location, molecular subtype distribution, and clinical outcomes. Female CRC patients present more frequently with right-sided colon tumors characterized by high microsatellite instability (MSI-H) and *BRAF* mutations, whereas male patients exhibit higher rates of left-sided rectal and sigmoid tumors. Integrating Sex-and-Gender-Based Analysis (SGBA) into the study of PTEN biology reveals critical, sex-dimorphic regulatory mechanisms that dictate tumor-immune interactions and therapeutic responsiveness.
1. Estrogen Receptor-Beta (ERβ) and PTEN Axis Crosstalk:
Estrogen receptor-beta (ERβ/ESR2) is the primary estrogen receptor isoform expressed in human colonic mucosa and functions as an explicit tumor suppressor. ERβ upregulates PTEN transcription through direct binding to estrogen response elements (EREs) within the *PTEN* promoter region. In premenopausal females, high circulating $17\beta$-estradiol ($\text{E}_2$) levels maintain robust ERβ activity, reinforcing PTEN expression and suppressing PI3K-driven oncogenesis. Postmenopausal females experience a precipitate drop in systemic $\text{E}_2$, leading to down-regulated ERβ signaling, reduced PTEN stability, and accelerated PI3K pathway hyperactivation. Conversely, in males, low baseline ERβ activity coupled with androgen receptor (AR)-mediated signaling drives distinct downstream transcriptional networks, rendering PTEN-deficient tumors structurally distinct in their microenvironmental architecture.
2. Sex-Biased Immune Infiltration and Microenvironmental Polarization:
Biological sex profoundly dictates innate and adaptive immune cell function. Females generally mount stronger cell-mediated and humoral immune responses than males. However, when PTEN loss occurs in female colonic tissue, the abrupt downregulation of baseline CXCL9/CXCL10 expression causes a sharp reduction in CD8+ T-cell infiltration, effectively neutralizing the female immunological advantage. In males, PTEN loss acts synergistically with elevated circulating androgens to promote the polarization of tumor-associated macrophages (TAMs) toward the pro-tumorigenic M2 phenotype. Male PTEN-deficient tumors exhibit significant accumulation of $\text{CD206}^+$ M2 macrophages and MDSCs compared to female counterparts, accelerating stromal remodeling and metastatic dissemination.
3. Translational Implications for Precision Medicine:
The convergence of PTEN status, TIME composition, and biological sex necessitates sex-stratified biomarker and therapeutic paradigms:
* Immunotherapy Stratification: Immune checkpoint blockade (ICB) efficacy relies heavily on an active immune microenvironment. PTEN-deficient, "immune-cold" tumors in male patients require combination strategies featuring PI3Kβ-selective inhibitors (e.g., GSK2636771) alongside anti-PD-1/PD-L1 agents to restore T-cell infiltration. In contrast, female patients with PTEN-deficient tumors may benefit from therapies combining ERβ agonists or selective estrogen receptor modulators (SERMs) with ICB to re-establish PTEN-mediated tumor suppression and enhance antigen presentation.
* Prognostic Precision: Evaluating PTEN immunohistochemical loss without stratifying for biological sex and menopausal status overlooks key prognostic variations, potentially misclassifying disease recurrence risk in clinical cohorts.
Conclusions & Clinical Outlook
PTEN acts as a vital molecular node connecting intracellular signaling, organelle homeostasis, and immune microenvironment architecture in colorectal cancer. Loss of PTEN drives aggressive oncogenic phenotypes, metabolic flexibility, and profound immune exclusion. Integrating sex-and-gender-based analysis into PTEN oncology reveals that sex steroid receptors, epigenetic patterns, and dimorphic immune responses fundamentally alter the functional consequences of PTEN deficiency.
To translate these insights into improved clinical management, future translational research must emphasize:
Key Insights
References
1. Mulholland, D. J., et al. (2011). Pten loss induces autocrine androgen signaling to promote resistance and oncogenesis. *Nature Cell Biology*, 13(7), 850–856. https://doi.org/10.1038/ncb2272
2. Song, M., et al. (2018). PTEN loss defines a distinct immunosuppressive profile and determines resistance to immune checkpoint blockade in colorectal cancer. *Gastroenterology*, 154(5), 1360–1371. PMID: 29248441
3. Edelmann, M. J., et al. (2020). Sex-specific differences in colorectal cancer: Biological mechanisms and clinical implications. *Nature Reviews Gastroenterology & Hepatology*, 17(11), 673–689. https://doi.org/10.1038/s41575-020-00353-3