Clinical development of therapies targeting TGFβ: current knowledge and future perspectives.

The mammary gland is a highly dynamic organ that undergoes profound changes within its epithelium during puberty and the reproductive cycle. These changes are fueled by dedicated stem and progenitor cells. Both short- and long-lived lineage-restricted progenitors have been identified in adult tissue as well as a small pool of multipotent mammary stem cells (MaSCs), reflecting intrinsic complexity within the epithelial hierarchy. While unipotent progenitor cells predominantly execute day-to-day homeostasis and postnatal morphogenesis during puberty and pregnancy, multipotent MaSCs have been implicated in coordinating alveologenesis and long-term ductal maintenance. Nonetheless, the multipotency of stem cells in the adult remains controversial. The advent of large-scale single-cell molecular profiling has revealed striking changes in the gene expression landscape through ontogeny and the presence of transient intermediate populations. An increasing number of lineage cell-fate determination factors and potential niche regulators have now been mapped along the hierarchy, with many implicated in breast carcinogenesis. The emerging diversity among stem and progenitor populations of the mammary epithelium is likely to underpin the heterogeneity that characterizes breast cancer.

https://journals.physiology.org/doi/pdf/10.1152/physrev.00040.2018

Stem Cells and the Differentiation Hierarchy in Mammary Gland Development

Cancer-related diseases represent the second overall cause of death worldwide. Human papilloma virus (HPV) is an infectious agent which is mainly sexually transmitted and may lead to HPV-associated cancers in both men and women. Almost all cervical cancers are HPV-associated, however, an increasing number of head and neck cancers (HNCs), especially oropharyngeal cancer, can be linked to HPV infection. Moreover, anogenital cancers, including vaginal, vulvar, penial, and anal cancers, represent a subset of HPV-related cancers. Whereas testing and prevention of cervical cancer have significantly improved over past decades, anogenital cancers remain more difficult to confirm. Current clinical trials including patients with HPV-related cancers focus on finding proper testing for all HPV-associated cancers as well as improve the currently applied treatments. The HPV viral oncoproteins, E6 and E7, lead to degradation of, respectively, p53 and pRb resulting in entering the S phase without G1 arrest. These high-risk HPV viral oncogenes alter numerous cellular processes, including DNA repair, angiogenesis, and/or apoptosis, which eventually result in carcinogenesis. Additionally, a comprehensive analysis of gene expression and alteration among a panel of DNA double strand breaks (DSB) repair genes in HPV-negative and HPV-positive HNC cancers reveals differences pointing to HPV-dependent modifications of DNA repair processes in these cancers. In this review, we discuss the current knowledge regarding HPV-related cancers, current screening, and treatment options as well as DNA damage response-related biological aspects of the HPV infection and clinical trials.

http://www.cancerbiomed.org/index.php/cocr/article/download/1747/1706

Biological and clinical aspects of HPV-related cancers

TGF-β in radiotherapy: Mechanisms of tumor resistance and normal tissues injury

Purpose: Following cytotoxic therapy, 70% of patients with human papillomavirus (HPV) positive oropharyngeal head and neck squamous cell carcinoma (HNSCC) are alive at 5 years compared to 30% of those with similar HPV-negative cancer, which is thought to be due to dysregulation of DNA repair. Loss of transforming growth factor β (TGFβ) signaling is a poorly studied consequence of HPV that could contribute to this phenotype. Experimental Design: Human HNSCC cell lines (n=9), patient-derived xenografts (n=9), tissue microarray (n=194), TCGA expression data and primary tumor specimens (n=10) were used to define the relationship between TGFβ competency, response to DNA damage, and type of DNA repair. Results: Analysis of HNSCC specimens in situ and in vitro showed that HPV associates with loss of TGFβ signaling that increases the response to radiation or cisplatin. TGFβ suppressed miR-182 that inhibited both BRCA1, necessary for homologous recombination repair, and FOXO3, which is required for ATM kinase activity. TGFβ signaling blockade by either HPV or inhibitors released this control, compromised HRR and increased response to PARP inhibition. Antagonizing miR-182 rescued the homologous recombination deficit in HPV+ cells. Loss of TGFβ signaling unexpectedly increased error-prone, alternative end-joining repair. Conclusions: HPV-positive HNSCC cells are unresponsive to TGFβ. Abrogated TGFβ signaling compromises homologous recombination and shifts reliance on alt-EJ repair that provides a mechanistic basis for sensitivity to PARP inhibitors. The effect of HPV in HNSCC provides critical validation of TGFβ9s role in DNA repair proficiency and further raises the translational potential of TGFβ inhibitors in cancer therapy.

/pdf/subjugation-of-tgfb-signaling-by-human-papilloma-virus-in-3qvoaeg62p.pdf

Subjugation of TGFβ Signaling by Human Papilloma Virus in Head and Neck Squamous Cell Carcinoma Shifts DNA Repair from Homologous Recombination to Alternative End Joining.

Maintenance of mammary functional capacity during cycles of proliferation and regression depends on appropriate cell fate decisions of mammary progenitor cells to populate an epithelium consisting of secretory luminal cells and contractile myoepithelial cells. It is well established that transforming growth factor-β (TGFβ) restricts mammary epithelial cell proliferation and that sensitivity to TGFβ is decreased in breast cancer. We show that TGFβ also exerts control of mammary progenitor self-renewal and lineage commitment decisions by stringent regulation of breast cancer associated 1 (BRCA1), which controls stem cell self-renewal and lineage commitment. Either genetic depletion of Tgfb1 or transient blockade of TGFβ increased self-renewal of mammary progenitor cells in mice, cultured primary mammary epithelial cells, and also skewed lineage commitment toward the myoepithelial fate. TGFβ stabilized the abundance of BRCA1 by reducing the abundance of microRNA-182 (miR-182). Ectopic expression of BRCA1 or antagonism of miR-182 in cultured TGFβ-deficient mammary epithelial cells restored luminal lineage commitment. These findings reveal that TGFβ modulation of BRCA1 directs mammary epithelial cell fate and, because stem or progenitor cells are thought to be the cell of origin for aggressive breast cancer subtypes, suggest that TGFβ dysregulation during tumorigenesis may promote distinct breast cancer subtypes.

https://escholarship.org/content/qt6h62b466/qt6h62b466.pdf?t=onkqy2

A TGFβ–miR-182–BRCA1 axis controls the mammary differentiation hierarchy

Purpose: Following cytotoxic therapy, 70% of patients with human papillomavirus (HPV) positive oropharyngeal head and neck squamous cell carcinoma (HNSCC) are alive at 5 years compared to 30% of those with similar HPV-negative cancer, which is thought to be due to dysregulation of DNA repair. Loss of transforming growth factor β (TGFβ) signaling is a poorly studied consequence of HPV that could contribute to this phenotype.
Experimental Design: Human HNSCC cell lines (n=9), patient-derived xenografts (n=9), tissue microarray (n=194), TCGA expression data and primary tumor specimens (n=10) were used to define the relationship between TGFβ competency, response to DNA damage, and type of DNA repair. 
Results: Analysis of HNSCC specimens in situ and in vitro showed that HPV associates with loss of TGFβ signaling that increases the response to radiation or cisplatin. TGFβ suppressed miR-182 that inhibited both BRCA1, necessary for homologous recombination repair, and FOXO3, which is required for ATM kinase activity. TGFβ signaling blockade by either HPV or inhibitors released this control, compromised HRR and increased response to PARP inhibition. Antagonizing miR-182 rescued the homologous recombination deficit in HPV+ cells. Loss of TGFβ signaling unexpectedly increased error-prone, alternative end-joining repair. 
Conclusions: HPV-positive HNSCC cells are unresponsive to TGFβ. Abrogated TGFβ signaling compromises homologous recombination and shifts reliance on alt-EJ repair that provides a mechanistic basis for sensitivity to PARP inhibitors. The effect of HPV in HNSCC provides critical validation of TGFβ9s role in DNA repair proficiency and further raises the translational potential of TGFβ inhibitors in cancer therapy.

https://www.biorxiv.org/content/biorxiv/early/2018/06/26/353441.full.pdf

Subjugation of TGFβ Signaling by Human Papilloma Virus in Head and Neck Squamous Cell Carcinoma Shifts DNA Repair from Homologous Recombination to Alternative End-Joining

Qi Liu

Papers

Subjugation of TGFβ Signaling by Human Papilloma Virus in Head and Neck Squamous Cell Carcinoma Shifts DNA Repair from Homologous Recombination to Alternative End Joining.

A TGFβ–miR-182–BRCA1 axis controls the mammary differentiation hierarchy

Subjugation of TGFβ Signaling by Human Papilloma Virus in Head and Neck Squamous Cell Carcinoma Shifts DNA Repair from Homologous Recombination to Alternative End-Joining