The clinical manifestations and molecular pathogenesis of radiation fibrosis

Advances in radiation techniques have enabled the precise delivery of higher doses of radiotherapy to tumours, while sparing surrounding healthy tissues. Consequently, the incidence of radiation toxicities has declined, and will likely continue to improve as radiotherapy further evolves. Nonetheless, ionizing radiation elicits tissue-specific toxicities that gradually develop into radiation-induced fibrosis, a common long-term side-effect of radiotherapy. Radiation fibrosis is characterized by an aberrant wound repair process, which promotes the deposition of extensive scar tissue, clinically manifesting as a loss of elasticity, tissue thickening, and organ-specific functional consequences. In addition to improving the existing technologies and guidelines directing the administration of radiotherapy, understanding the pathogenesis underlying radiation fibrosis is essential for the success of cancer treatments. This review integrates the principles for radiotherapy dosimetry to minimize off-target effects, the tissue-specific clinical manifestations, the key cellular and molecular drivers of radiation fibrosis, and emerging therapeutic opportunities for both prevention and treatment.

CD8+ Tumor-Infiltrating Lymphocyte Abundance Is a Positive Prognostic Indicator in Nasopharyngeal Cancer

PURPOSE

Tumor-infiltrating lymphocytes (TIL) are immune cell populations found within tumors, critical in the antigen-specific host immune response. In this study, we aimed to elucidate the prognostic significance of CD3+, CD4+, and CD8+ TILs in nasopharyngeal cancer (NPC).

EXPERIMENTAL DESIGN

Immune cell infiltration was quantified in NPC samples (n = 50) using RNA-sequencing (RNA-seq) data based on rearranged T-cell receptor (TCR) reads and the Estimation of Stromal and Immune cells in malignant tumors using expression data (ESTIMATE) immune score tool. The differential abundances of TIL subset populations were also characterized through IHC staining of formalin-fixed, paraffin-embedded samples from a training cohort (n = 35), which was a subset of the RNA-seq cohort (n = 50).

RESULTS

In the RNA-seq cohort, patients with higher rearranged TCR reads experienced superior 5- and 10-year overall survival (OS; P < 0.001), and disease-free survival (DFS; P < 0.001). Similarly, patients with higher ESTIMATE immune scores experienced superior 5- and 10-year OS (P = 0.024) and DFS (P = 0.007). In the training cohort, high abundances of CD8+ TILs were significantly associated with improved 5- and 10-year OS (P = 0.003) and DFS (P = 0.005). These findings were corroborated in an independent validation cohort (n = 84), and combined analysis of the training and validation cohorts [n = 119 (35+84)], which further demonstrated improved 5- and 10-year survival in terms of locoregional control (P < 0.001) and distant metastasis (P = 0.03).

CONCLUSIONS

Taken together, our study highlights the prognostic value of CD8+ TILs in NPC, and the potential of future investigations into cellular-based immunotherapies employing CD8+ lymphocytes.

MiR-34c downregulation leads to SOX4 overexpression and cisplatin resistance in nasopharyngeal carcinoma

Background

A major cause of disease-related death in nasopharyngeal carcinoma (NPC) is the development of distant metastasis (DM) despite combination chemoradiotherapy treatment. We previously identified and validated a four microRNA (miRNA) signature that is prognostic for DM. In this study, characterization of a key component of this signature, miR-34c, revealed its role in chemotherapy resistance.

Methods

Two hundred forty-six NPC patient biopsy samples were subject to comprehensive miRNA profiling and immunohistochemistry (IHC). Two human normal nasopharyngeal cell lines (immortalized; NP69 and NP460), as well as the NPC cell line C666–1, were used for miR-34c gain-of-function and loss-of-function experiments. Signaling pathways were assessed using quantitative real-time PCR (qRT-PCR) and Western blot. Cell viability was measured using the ATPlite assay.

Results

MiR-34c was downregulated in NPC patient samples, and confirmed in vitro to directly target SOX4, a master regulator of epithelial-to-mesenchymal transition (EMT). MiR-34c downregulation triggered EMT-representative changes in NP69 and NP460 whereby Snail, ZEB1, CDH2, and SOX2 were upregulated, while Claudin-1 and CDH1 were downregulated. Phenotypically, inhibition of miR-34c led to cisplatin resistance, whereas miR-34c over-expression sensitized NPC cells to cisplatin. TGFβ1 decreased miR-34c and increased SOX4 expression in vitro. The TGFβ receptor 1 inhibitor SB431542 reduced SOX4 expression and increased cisplatin sensitivity. Finally, IHC revealed that lower SOX4 expression was associated with improved overall survival in chemotherapy-treated NPC patients.

Conclusion

miR-34c is downregulated in NPC. Repression of miR-34c was shown to increase SOX4 expression, which leads to cisplatin resistance, while TGFβ1 was found to repress miR-34c expression. Taken together, our study demonstrates that inhibition of the TGFβ1 pathway could be a strategy to restore cisplatin sensitivity in NPC.

Blocking SHH/Patched Interaction Triggers Tumor Growth Inhibition through Patched-Induced Apoptosis

The Sonic Hedgehog (SHH) pathway plays a key role in cancer. Alterations of SHH canonical signaling, causally linked to tumor progression, have become rational targets for cancer therapy. However, Smoothened (SMO) inhibitors have failed to show clinical benefit in patients with cancers displaying SHH autocrine/paracrine expression. We reported earlier that the SHH receptor Patched (PTCH) is a dependence receptor that triggers apoptosis in the absence of SHH through a pathway that differs from the canonical one, thus generating a state of dependence on SHH for survival. Here, we propose a dual function for SHH: its binding to PTCH not only activates the SHH canonical pathway but also blocks PTCH-induced apoptosis. Eighty percent, 64%, and 8% of human colon, pancreatic, and lung cancer cells, respectively, overexpressed SHH at transcriptional and protein levels. In addition, SHH-overexpressing cells expressed all the effectors of the PTCH-induced apoptotic pathway. Although the canonical pathway remained unchanged, autocrine SHH interference in colon, pancreatic, and lung cell lines triggered cell death through PTCH proapoptotic signaling. In vivo, SHH interference in colon cancer cell lines decreased primary tumor growth and metastasis. Therefore, the antitumor effect associated to SHH deprivation, usually thought to be a consequence of the inactivation of the canonical SHH pathway, is, at least in part, because of the engagement of PTCH proapoptotic activity. Together, these data strongly suggest that therapeutic strategies based on the disruption of SHH/PTCH interaction in SHH-overexpressing cancers should be explored. SIGNIFICANCE: Sonic Hedgehog-overexpressing tumors express PTCH-induced cell death effectors, suggesting that this death signaling could be activated as an antitumor strategy.

Dysregulation of the MiR-449b target TGFBI alters the TGFβ pathway to induce cisplatin resistance in nasopharyngeal carcinoma

Despite the improvement in locoregional control of nasopharyngeal carcinoma (NPC), distant metastasis (DM), and chemoresistance persist as major causes of mortality. This study identified a novel role for miR-449b, an overexpressed gene in a validated four-miRNA signature for NPC DM, leading to chemoresistance via the direct targeting of transforming growth factor beta-induced (TGFBI). In vitro shRNA-mediated downregulation of TGFBI induced phosphorylation of PTEN and AKT, increasing cisplatin resistance. Conversely, the overexpression of TGFBI sensitized the NPC cells to cisplatin. In NPC patients treated with concurrent chemoradiotherapy (CRT), the overall survival (OS) was significantly inversely correlated with miR-449b, and directly correlated with both TGFBI mRNA and protein expression, as assessed by RNA sequencing and immunohistochemistry (IHC). Mechanistically, co-immunoprecipitation demonstrated that TGFBI competes with pro-TGFβ1 for integrin receptor binding. Decreased TGFBI led to increased pro-TGFβ1 activation and TGFβ1 canonical/noncanonical pathway-induced cisplatin resistance. Thus, overexpression of miR-449b decreases TGFBI, thereby altering the balance between TGFBI and pro-TGFβ1, revealing a novel mechanism of chemoresistance in NPC.

MiR-449a promotes breast cancer progression by targeting CRIP2

The identification of prognostic biomarkers and their underlying mechanisms of action remain of great interest in breast cancer biology. Using global miRNA profiling of 71 lymph node-negative invasive ductal breast cancers and 5 normal mammary epithelial tissues, we identified miR-449a to be highly overexpressed in the malignant breast tissue. Its expression was significantly associated with increased incidence of patient relapse, decreased overall survival, and decreased disease-free survival. In vitro, miR-449a promoted breast cancer cell proliferation, clonogenic survival, migration, and invasion. By utilizing a tri-modal in silico approach for target identification, Cysteine-Rich Protein 2 (CRIP2; a transcription factor) was identified as a direct target of miR-449a, corroborated using qRT-PCR, Western blot, and luciferase reporter assays. MDA-MB-231 cells stably transfected with CRIP2 demonstrated a significant reduction in cell viability, migration, and invasion, as well as decreased tumor growth and angiogenesis in mouse xenograft models. Our data revealed that overexpression of miR-449a suppresses CRIP2, which then affects the tumor vasculature, likely via NF-κB/p65 complex-mediated transcription of VEGF. These finding define an oncogenic function of miR-449a in human breast cancer, and highlight the importance of this pathway in driving aggressive behaviour.

Abstract 5038: The repression of the extracellular matrix protein TGFBI induces chemoresistance in nasopharyngeal carcinoma

Introduction: Nasopharyngeal carcinoma (NPC) is a malignancy that is strongly associated with Epstein-Barr virus (EBV). The five-year overall survival (OS) rate of locally-advanced NPC patients is ∼65%. Therapeutic options for such patients are limited; ionizing radiation is the primary mode of therapy for early-stage NPC, while chemoradiotherapy is used for more advanced stages. The use of chemotherapy (combined with radiation) provides a modest benefit in OS, but causes significant toxicities. The major cause of death in NPC is distant metastasis (DM), which remains a clinical challenge. In order to identify novel mechanisms underlying this process, our laboratory has recently completed global RNA sequencing of NPC samples which were fully clinically annotated. The extracellular matrix protein TGFBI (Transforming Growth Factor, Beta-Induced) was identified as a potential marker for chemoresistance. The objective of this study was to elucidate the role of TGFBI, and acquire greater insight into the biological pathways leading to chemoresistance and contributing to DM in NPC.

Methods: Nasopharyngeal cell lines including NP69 (normal nasopharyngeal, SV-40 immortalized), and C666-1 (NPC, EBV positive) were used to assess the differential expression of TGFBI between normal and malignant cells. TGFBI under-expressing NP69 cells were engineered using shRNA vectors, and the impact of the loss of TGFBI expression was assessed by cell death, clonogenic, and migration assays. Downstream target gene expression was evaluated by quantitative real-time PCR (qRT-PCR) and Western blot. C666-1 cells, which had no expression of TGFBI (RNA or protein), were used as controls.

Results: RNA-seq data identified poorer distant relapse-free survival in chemoradiotherapy-treated patients with low TGFBI expression vs. those with high TGFBI expression. In concordance with this observation, in vitro down-regulation of TGFBI induced cisplatin resistance via the phosphorylation of Akt and PTEN. TGFBI downregulation also increased cellular migration in spheroid cultures. Furthermore, TGFBI was identified to be a target of miR-449b, one of the 4 microRNAs in a DM prognostic signature that was previously identified by our group (Oncotarget 6:4537, 2015). In turn, over-expression of miR-449b in nasopharyngeal cells increased phospho-Akt expression, phenocopying the results observed in the TGFBI experiments.

Conclusion: Together, these data suggest that the miR-449∼TGFBI-Akt axis plays a significant role in both treatment resistance and metastasis in NPC. Further studies will allow us to elucidate additional components of this pathway, and identify novel therapeutic targets which can benefit future patients with NPC.

Citation Format: Pierre-Antoine Bissey, Jeff W. Bruce, Jacqueline Law, Kenneth W. Yip, Fei-Fei Liu. The repression of the extracellular matrix protein TGFBI induces chemoresistance in nasopharyngeal carcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5038.