Concomitant activation of GLI1 and Notch1 contributes to racial disparity of human triple negative breast cancer progression

Mortality from triple negative breast cancer (TNBC) is significantly higher in African American (AA) women compared to White American (WA) women emphasizing ethnicity as a major risk factor; however, the molecular determinants that drive aggressive progression of AA-TNBC remain elusive. Here, we demonstrate for the first time that AA-TNBC cells are inherently aggressive, exhibiting elevated growth, migration, and cancer stem-like phenotype compared to WA-TNBC cells. Meta-analysis of RNA-sequencing data of multiple AA- and WA-TNBC cell lines shows enrichment of GLI1 and Notch1 pathways in AA-TNBC cells. Enrichment of GLI1 and Notch1 pathway genes was observed in AA-TNBC. In line with this observation, analysis of TCGA dataset reveals a positive correlation between GLI1 and Notch1 in AA-TNBC and a negative correlation in WA-TNBC. Increased nuclear localization and interaction between GLI1 and Notch1 is observed in AA-TNBC cells. Of importance, inhibition of GLI1 and Notch1 synergistically improves the efficacy of chemotherapy in AA-TNBC cells. Combined treatment of AA-TNBC-derived tumors with GANT61, DAPT, and doxorubicin/carboplatin results in significant tumor regression, and tumor-dissociated cells show mitigated migration, invasion, mammosphere formation, and CD44⁺/CD24^- population. Indeed, secondary tumors derived from triple-therapy-treated AA-TNBC tumors show diminished stem-like phenotype. Finally, we show that TNBC tumors from AA women express significantly higher level of GLI1 and Notch1 expression in comparison to TNBC tumors from WA women. This work sheds light on the racial disparity in TNBC, implicates the GLI1 and Notch1 axis as its functional mediators, and proposes a triple-combination therapy that can prove beneficial for AA-TNBC.

Abstract C23: High Kaiso expression correlates with increased TGFβ signaling and aggressive TNBC in women of African Ancestry (WAA)

Despite increased awareness, early detection and improved therapies in the past 20 years, breast cancer (BC) remains the most frequent female cancer and a leading cause of female deaths worldwide. One of the most clinically challenging BC is the Triple Negative Breast Cancer (TNBC) subtype that is estrogen receptor (ER), progesterone receptor (PR) & human epidermal growth factor receptor-2 (HER2) negative. TNBC tumors are aggressive and metastatic, and have a poor prognosis since they cannot be treated with standard therapies (Tamoxifen or Herceptin). Intriguingly TNBC is most prevalent in young women of African Ancestry (WAA) who, despite having lower BC incidence rates than Caucasian women, have higher mortality rates. The propensity of TNBC to metastasize suggests a deregulation of the epithelial-to-mesenchymal transition (EMT) pathway that endows cells with increased motility, and is implicated in tumor progression. Our lab and others recently found a significant correlation between high expression of the POZ-ZF transcription factor Kaiso, EMT, estrogen receptor (ER) negativity in WAA, and shorter metastasis-free survival. Notably when Kaiso is depleted in TNBC cell lines, the cells exhibited decreased TGFβ signaling (a known promoter of EMT), become less motile and invasive in vitro, and did not metastasize to lungs or liver in mouse xenograft models. These findings led us to hypothesize that Kaiso plays a role in the spread of aggressive BC possibly via up-regulation of TGFβ signaling.

To gain insight into Kaiso's role in aggressive breast cancers and the racial disparity associated with BC outcomes, we generated a tissue microarray (TMA) comprised of TNBC tissues from Barbadian and Nigerian WAA, and performed expression profiling of Kaiso and various TGFβ signaling proteins (TGFβR1, TGFβR2 and p-Smad2) on the WAA-TMA. We found that high Kaiso expression correlated positively with increased TGFβ signalling in WAA TNBC tissues, thus supporting our hypothesis that Kaiso plays a role in TGFβ signaling and TNBC aggressiveness. Notably, we also observed that Kaiso depletion resulted in delayed onset of mouse xenograft tumors derived from MDA-231 TNBC cells. Mechanistic in vitro studies further revealed that Kaiso depletion reduced cell proliferation and increased apoptosis of TNBC cells, especially in response to the DNA-damaging drug Etoposide.

Our findings linking high Kaiso expression to TNBC cell survival and active TGFβ signalling in aggressive TNBCs from WAA, raises the exciting possibility that Kaiso may be developed as a diagnostic and prognostic marker for TNBC patients regardless of race. Ongoing experiments are focused on elucidating Kaiso's exact role in aggressive breast tumors and the racial disparities in breast cancer outcomes.

Citation Format: Blessing I. Bassey-Archibong, Lyndsay GA Rayner, Shawn Hercules, Sinthu Pathmanapan, Juliet M. Daniel. High Kaiso expression correlates with increased TGFβ signaling and aggressive TNBC in women of African Ancestry (WAA). [abstract]. In: Proceedings of the Ninth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2016 Sep 25-28; Fort Lauderdale, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2017;26(2 Suppl):Abstract nr C23.

Thoracic intradural extramedullary capillary haemangioma

The authors report a rare case of thoracic intradural extramedullary capillary haemangioma, the clinical presentation of which was similar to any other intraspinal mass. Magnetic resonance imaging does not always distinguish this entity from others, but the presence of enlarged vasculature is often a useful clue. Complete resection is the treatment of choice of this hamartomatous lesion.