School of Medicine and Health Sciences Poster Presentations

Title

Enhancing the effect of immunotherapy by inhibiting tumor promoting effect of HDAC6

Document Type

Poster

Abstract Category

Cancer/Oncology

Keywords

Triple negative breast cancer, metastasis, epithelial mesenchymal transition, gene signature

Publication Date

Spring 5-1-2019

Abstract

Histone deacetylases (HDAC) perform diverse functions beyond remodeling of chromatin landscape. It ranges from regulating the cellular-health to immune-diseases like cancer, positioning the HDAC inhibitors (HDACi) at a crucial junction of immunotherapy. The toxicity among pan-HDACi has led to the development of selective inhibitors, which helped to understand the roles of specific HDACs in immune responses. For example, HDAC6 promotes the pro-tumorigenic STAT3 pathway. By using specific HDAC6i, the downstream immune-modulatory pathways of STAT3, such as PDL1, could be targeted. HDAC6 has been associated with numerous structural functions, including cellular motility, shape, and intracellular transport through the acetylation of tubulin and cortactin. This function suggests that HDAC6 could also be a regulator of metastasis. We found that the selective HDAC6i NextA was able to reduce the primary tumor growth and the appearance of spontaneously metastatic nodules in the murine Triple Negative Breast Cancer (TNBC) tumor model 4T1. Additionally, the in vitro use of NextA in multiple murine and human breast cancer cell lines was found to reduce invasion and modulate multiple EMT-specific genes without exhibiting excessive cytotoxicity. PDL1 expression was also reduced, as described previously in melanoma models. In vivo, NextA reduced both the primary and secondary tumor progression. Given that 4T1 is a TIL-infiltrated tumor, we tested the efficacy of ÔÅ°PD-1 immune checkpoint inhibitors (ICI) and found a lower dose of ÔÅ°PD-1 to be more effective than the higher doses to reduce primary and secondary tumor growth. However, the expression of IFNÔÅß & PD-L1 were enhanced with the monotherapy. In an in vitro setting, we were able to nullify the upregulation of PD-L1 by ÔÅ°PD-1 with either NextA or IFNÔÅß neutralization. To apply this insight in vivo, we tested the combination of NextA and ÔÅ°PD-1 to find a significant reduction in tumor growth, both in primary & secondary nodules. Analysis of the effector molecules revealed a reduction in intra-tumoral PD-L1 and IDO1 as well as a reduction in several key EMT signature genes, including cMYC, MMP9, vimentin, and twist. We identified E-cadherin, a negative regulator metastasis, upregulated in vivo with NextA. This was corroborated by in vitro observations in several murine and human breast cancer cell lines, irrespective of hormonal receptor status. In conclusion, we propose that combining HDAC6i along with ICI such as ÔÅ°PD-1 may offer a novel avenue to enhance the efficacy of immunotherapy, and alter tumor-intricate physiology, without incurring unnecessary toxicity.

Open Access

1

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Presented at Research Days 2019.

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Enhancing the effect of immunotherapy by inhibiting tumor promoting effect of HDAC6

Histone deacetylases (HDAC) perform diverse functions beyond remodeling of chromatin landscape. It ranges from regulating the cellular-health to immune-diseases like cancer, positioning the HDAC inhibitors (HDACi) at a crucial junction of immunotherapy. The toxicity among pan-HDACi has led to the development of selective inhibitors, which helped to understand the roles of specific HDACs in immune responses. For example, HDAC6 promotes the pro-tumorigenic STAT3 pathway. By using specific HDAC6i, the downstream immune-modulatory pathways of STAT3, such as PDL1, could be targeted. HDAC6 has been associated with numerous structural functions, including cellular motility, shape, and intracellular transport through the acetylation of tubulin and cortactin. This function suggests that HDAC6 could also be a regulator of metastasis. We found that the selective HDAC6i NextA was able to reduce the primary tumor growth and the appearance of spontaneously metastatic nodules in the murine Triple Negative Breast Cancer (TNBC) tumor model 4T1. Additionally, the in vitro use of NextA in multiple murine and human breast cancer cell lines was found to reduce invasion and modulate multiple EMT-specific genes without exhibiting excessive cytotoxicity. PDL1 expression was also reduced, as described previously in melanoma models. In vivo, NextA reduced both the primary and secondary tumor progression. Given that 4T1 is a TIL-infiltrated tumor, we tested the efficacy of ÔÅ°PD-1 immune checkpoint inhibitors (ICI) and found a lower dose of ÔÅ°PD-1 to be more effective than the higher doses to reduce primary and secondary tumor growth. However, the expression of IFNÔÅß & PD-L1 were enhanced with the monotherapy. In an in vitro setting, we were able to nullify the upregulation of PD-L1 by ÔÅ°PD-1 with either NextA or IFNÔÅß neutralization. To apply this insight in vivo, we tested the combination of NextA and ÔÅ°PD-1 to find a significant reduction in tumor growth, both in primary & secondary nodules. Analysis of the effector molecules revealed a reduction in intra-tumoral PD-L1 and IDO1 as well as a reduction in several key EMT signature genes, including cMYC, MMP9, vimentin, and twist. We identified E-cadherin, a negative regulator metastasis, upregulated in vivo with NextA. This was corroborated by in vitro observations in several murine and human breast cancer cell lines, irrespective of hormonal receptor status. In conclusion, we propose that combining HDAC6i along with ICI such as ÔÅ°PD-1 may offer a novel avenue to enhance the efficacy of immunotherapy, and alter tumor-intricate physiology, without incurring unnecessary toxicity.