Chk2*1100delC Acts in synergy with the Ron receptor tyrosine kinase to accelerate mammary tumorigenesis in mice

Molecular portraits of cell cycle checkpoint kinases in cancer evolution, progression, and treatment responsiveness

Cell cycle dysregulation is prerequisite for cancer formation. However, it is unknown whether the mode of dysregulation affects disease characteristics. Here, we conduct comprehensive analyses of cell cycle checkpoint dysregulation using patient data and experimental investigations. We find that ATM mutation predisposes the diagnosis of primary estrogen receptor (ER)+/human epidermal growth factor (HER)2- cancer in older women. Conversely, CHK2 dysregulation induces formation of metastatic, premenopausal ER+/HER2- breast cancer (P = 0.001) that is treatment-resistant (HR = 6.15, P = 0.01). Lastly, while mutations in ATR alone are rare, ATR/TP53 co-mutation is 12-fold enriched over expected in ER+/HER2- disease (P = 0.002) and associates with metastatic progression (HR = 2.01, P = 0.006). Concordantly, ATR dysregulation induces metastatic phenotypes in TP53 mutant, not wild-type, cells. Overall, we identify mode of cell cycle dysregulation as a distinct event that determines subtype, metastatic potential, and treatment responsiveness, providing rationale for reconsidering diagnostic classification through the lens of the mode of cell cycle dysregulation..

USP39 regulates DNA damage response and chemo-radiation resistance by deubiquitinating and stabilizing CHK2

The serine/threonine kinase, CHK2 (checkpoint kinase 2), is a key mediator in DNA damage response and a tumor suppressor, which is implicated in promoting cell cycle arrest, apoptosis and DNA repair. Accumulating evidence suggests that these functions are primarily exerted through phosphorylation downstream factors such as p53 and BRCA1. Recent studies have shown that ubiquitination is an important mode of regulation of CHK2. However, it remains largely unclear whether deubiquitinases participate in regulation of CHK2. Here, we report that a deubiquitinase, USP39, is a new regulator of CHK2. Mechanistically, USP39 deubiquitinates and stabilizes CHK2, which in turn enhances CHK2 stability. Short hairpin RNA (shRNA) mediated knockdown of USP39 led to deregulate CHK2, which resulted in compromising the DNA damage-induced G2/M checkpoint, decreasing apoptosis, and conferring cancer cells resistance to chemotherapy drugs and radiation treatment. Collectively, we identify USP39 as a novel regulator of CHK2 in the DNA damage response.

Towards precision prevention: Technologies for identifying healthy individuals with high risk of disease

The rise of advanced technologies for characterizing human populations at the molecular level, from sequence to function, is shifting disease prevention paradigms toward personalized strategies. Because minimization of adverse outcomes is a key driver for treatment decisions for diseased populations, developing personalized therapy strategies represent an important dimension of both precision medicine and personalized prevention. In this commentary, we highlight recently developed enabling technologies in the field of DNA damage, DNA repair, and mutagenesis. We propose that omics approaches and functional assays can be integrated into population studies that fuse basic, translational and clinical research with commercial expertise in order to accelerate personalized prevention and treatment of cancer and other diseases linked to aberrant responses to DNA damage. This collaborative approach is generally applicable to efforts to develop data-driven, individualized prevention and treatment strategies for other diseases. We also recommend strategies for maximizing the use of biological samples for epidemiological studies, and for applying emerging technologies to clinical applications.

Hepatocyte growth factor-like protein is a positive regulator of early mammary gland ductal morphogenesis

The Ron receptor tyrosine kinase regulates multiple cellular processes and is important during mammary gland development and tumor progression. Hepatocyte growth factor-like protein [HGFL] is the only known ligand for the Ron receptor and recent studies have identified major roles for HGFL during breast cancer metastasis. Understanding the functional importance HGFL during mammary gland development will provide significant insights onto its contribution during tumor development and metastasis. In this study, we assessed the role of HGFL during postnatal mammary gland development using mice that were either proficient [HGFL +/+] or deficient [HGFL-/-] for HGFL. Postnatal ductal morphology and stromal cell associations were analyzed at multiple time points through puberty until adulthood. HGFL deficiency resulted in several mammary gland developmental defects including smaller terminal end buds [TEBs], significantly fewer TEBs, and delayed ductal outgrowth during early puberty. Additionally, HGFL deficient animals exhibited significantly altered TEB epithelial cell turnover with decreased proliferation and increased apoptosis coupled with decreased TEB diameter. Macrophage recruitment to the TEBs was also significantly decreased in the HGFL-/- mice compared to controls. Moreover, the levels of STAT3 mRNA as well as the phosphorylation status of this protein were lower in the HGFL-/- mammary glands compared to controls. Taken together, our data provide the first evidence for HGFL as a positive regulator of mammary gland ductal morphogenesis by controlling overall epithelial cell turnover, macrophage recruitment, and STAT3 activation in the developing mammary gland. With a function in early mammary gland development, HGFL represents a potential target for the development of novel breast cancer therapies.

Expression and mutational status of RON in neoplastic lesions of the breast: analysis of MSP/RON signaling in ductal carcinoma in situ and invasive ductal carcinoma

Recepteur d'origine nantais (RON) is a receptor tyrosine kinase closely related to MET and involved in tumorigenesis. We investigated the roles of aberrations in RON and its ligand, macrophage-stimulating protein (MSP), in invasive ductal carcinoma (IDC, n = 81), ductal carcinoma in situ (DCIS, n = 26), and in benign lesions (n = 20) of mammary gland. Expression of RON and MSP was evaluated by immunohistochemistry and the mutational status of a region containing the proteolytic cleavage site in exon 1 and each exon of the kinase domain (exon 14-20) of RON was screened by polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) analysis. The proportion of cases positive for RON expression was significantly different between malignant [86% (92/107)] and benign [40% (8/20)] lesions. RON expression was positive in both IDC and DCIS [90% (73/81) and 73% (19/26), respectively], whereas MSP expression was present in 54% (44/81) of IDC and absent in DCIS. RON expression correlated significantly with the histological grade of DCIS. No mutations were detected in the examined regions of RON in breast cancer samples as confirmed by PCR-SSCP. The findings suggest the involvement of RON expression in the development of breast cancer, and that an autocrine/paracrine loop of RON seems to affect tumor invasiveness.