Browsing by Author "Kannan, Nagarajan"

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    Onset of Telomere Dysfunction and Fusions in Human Ovarian Carcinoma
    (MDPI, 2019-05-04) Huda, Nazmul; Xu, Yan; Bates, Alison M.; Rankin, Deborah A.; Kannan, Nagarajan; Gilley, David; Pathology and Laboratory Medicine, School of Medicine
    Telomere dysfunction has been strongly implicated in the initiation of genomic instability and is suspected to be an early event in the carcinogenesis of human solid tumors. Recent findings have established the presence of telomere fusions in human breast and prostate malignancies; however, the onset of this genomic instability mechanism during progression of other solid cancers is not well understood. Herein, we explored telomere dynamics in patient-derived epithelial ovarian cancers (OC), a malignancy characterized by multiple distinct subtypes, extensive molecular heterogeneity, and widespread genomic instability. We discovered a high frequency of telomere fusions in ovarian tumor tissues; however, limited telomere fusions were detected in normal adjacent tissues or benign ovarian samples. In addition, we found relatively high levels of both telomerase activity and hTERT expression, along with anaphase bridges in tumor tissues, which were notably absent in adjacent normal ovarian tissues and benign lesions. These results suggest that telomere dysfunction may occur early in ovarian carcinogenesis and, importantly, that it may play a critical role in the initiation and progression of the disease. Recognizing telomere dysfunction as a pervasive feature of this heterogeneous malignancy may facilitate the future development of novel diagnostic tools and improved methods of disease monitoring and treatment.
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    Targeting LRRC15 Inhibits Metastatic Dissemination of Ovarian Cancer
    (American Association for Cancer Research, 2022) Ray, Upasana; Jung, Deok-Beom; Jin, Ling; Xiao, Yinan; Dasari, Subramanyam; Bhattacharya, Sayantani Sarkar; Thirusangu, Prabhu; Staub, Julie K.; Roy, Debarshi; Roy, Bhaskar; Weroha, S. John; Hou, Xiaonan; Purcell, James W.; Bakkum-Gamez, Jamie N.; Kaufmann, Scott H.; Kannan, Nagarajan; Mitra, Anirban K.; Shridhar, Viji; Medical and Molecular Genetics, School of Medicine
    Dissemination of ovarian cancer cells can lead to inoperable metastatic lesions in the bowel and omentum that cause patient death. Here we show that LRRC15, a type-I 15-leucine-rich repeat-containing membrane protein, highly overexpressed in ovarian cancer bowel metastases compared with matched primary tumors and acts as a potent promoter of omental metastasis. Complementary models of ovarian cancer demonstrated that LRRC15 expression leads to inhibition of anoikis-induced cell death and promotes adhesion and invasion through matrices that mimic omentum. Mechanistically, LRRC15 interacted with β1-integrin to stimulate activation of focal adhesion kinase (FAK) signaling. As a therapeutic proof of concept, targeting LRRC15 with the specific antibody-drug conjugate ABBV-085 in both early and late metastatic ovarian cancer cell line xenograft models prevented metastatic dissemination, and these results were corroborated in metastatic patient-derived ovarian cancer xenograft models. Furthermore, treatment of 3D-spheroid cultures of LRRC15-positive patient-derived ascites with ABBV-085 reduced cell viability. Overall, these data uncover a role for LRRC15 in promoting ovarian cancer metastasis and suggest a novel and promising therapy to target ovarian cancer metastases. Significance: This study identifies that LRRC15 activates β1-integrin/FAK signaling to promote ovarian cancer metastasis and shows that the LRRC15-targeted antibody-drug conjugate ABBV-085 suppresses ovarian cancer metastasis in preclinical models.
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    The Luminal Progenitor Compartment of the Normal Human Mammary Gland Constitutes a Unique Site of Telomere Dysfunction
    (Elsevier, 2013-06-04) Kannan, Nagarajan; Huda, Nazmul; Tu, LiRen; Droumeva, Radina; Aubert, Geraldine; Chavez, Elizabeth; Brinkman, Ryan R.; Lansdorp, Peter; Emerman, Joanne; Abe, Satoshi; Eaves, Connie; Gilley, David; Medical and Molecular Genetics, School of Medicine
    Telomeres are essential for genomic integrity, but little is known about their regulation in the normal human mammary gland. We now demonstrate that a phenotypically defined cell population enriched in luminal progenitors (LPs) is characterized by unusually short telomeres independently of donor age. Furthermore, we find that multiple DNA damage response proteins colocalize with telomeres in >95% of LPs but in <5% of basal cells. Paradoxically, 25% of LPs are still capable of exhibiting robust clonogenic activity in vitro. This may be partially explained by the elevated telomerase activity that was also seen only in LPs. Interestingly, this potential telomere salvage mechanism declines with age. Our findings thus reveal marked differences in the telomere biology of different subsets of primitive normal human mammary cells. The chronically dysfunctional telomeres unique to LPs have potentially important implications for normal mammary tissue homeostasis as well as the development of certain breast cancers.