Abstract:Leiomyosarcomas are rare and aggressive tumors characterized by a complex karyotype. Surgical resection with or without radiotherapy and chemotherapy is the standard curative treatment. Unfortunately, a high percentage of leiomyosarcomas recurs and metastasizes. In these cases, doxorubicin and ifosfamide represent the standard treatment but with low response rates. Here, we evaluated the induction of proteotoxic stress as a possible strategy to kill leiomyosarcoma cells in a therapeutic perspective. We show th… Show more
“…SAHA is the reference for a pan-HDAC inhibitor and zinc chelator. The results were comparable in the three cell lines, with SK-LMS-1 cells showing some resistance to cell death, as observed previously ( 14 ). Compounds MC2983 and MC2991, which are structurally related to NKL54 but should not act as zinc chelators, were significantly much less effective in inducing cell death (Figure 1C – E ).…”
In leiomyosarcoma class IIa HDACs (histone deacetylases) bind MEF2 and convert these transcription factors into repressors to sustain proliferation. Disruption of this complex with small molecules should antagonize cancer growth. NKL54, a PAOA (pimeloylanilide o-aminoanilide) derivative, binds a hydrophobic groove of MEF2, which is used as a docking site by class IIa HDACs. However, NKL54 could also act as HDAC inhibitor (HDACI). Therefore, it is unclear which activity is predominant. Here, we show that NKL54 and similar derivatives are unable to release MEF2 from binding to class IIa HDACs. Comparative transcriptomic analysis classifies these molecules as HDACIs strongly related to SAHA/vorinostat. Low expressed genes are upregulated by HDACIs, while abundant genes are repressed. This transcriptional resetting correlates with a reorganization of H3K27 acetylation around the transcription start site (TSS). Among the upregulated genes there are several BH3-only family members, thus explaining the induction of apoptosis. Moreover, NKL54 triggers the upregulation of MEF2 and the downregulation of class IIa HDACs. NKL54 also increases the binding of MEF2D to promoters of genes that are upregulated after treatment. In summary, although NKL54 cannot outcompete MEF2 from binding to class IIa HDACs, it supports MEF2-dependent transcription through several actions, including potentiation of chromatin binding.
“…SAHA is the reference for a pan-HDAC inhibitor and zinc chelator. The results were comparable in the three cell lines, with SK-LMS-1 cells showing some resistance to cell death, as observed previously ( 14 ). Compounds MC2983 and MC2991, which are structurally related to NKL54 but should not act as zinc chelators, were significantly much less effective in inducing cell death (Figure 1C – E ).…”
In leiomyosarcoma class IIa HDACs (histone deacetylases) bind MEF2 and convert these transcription factors into repressors to sustain proliferation. Disruption of this complex with small molecules should antagonize cancer growth. NKL54, a PAOA (pimeloylanilide o-aminoanilide) derivative, binds a hydrophobic groove of MEF2, which is used as a docking site by class IIa HDACs. However, NKL54 could also act as HDAC inhibitor (HDACI). Therefore, it is unclear which activity is predominant. Here, we show that NKL54 and similar derivatives are unable to release MEF2 from binding to class IIa HDACs. Comparative transcriptomic analysis classifies these molecules as HDACIs strongly related to SAHA/vorinostat. Low expressed genes are upregulated by HDACIs, while abundant genes are repressed. This transcriptional resetting correlates with a reorganization of H3K27 acetylation around the transcription start site (TSS). Among the upregulated genes there are several BH3-only family members, thus explaining the induction of apoptosis. Moreover, NKL54 triggers the upregulation of MEF2 and the downregulation of class IIa HDACs. NKL54 also increases the binding of MEF2D to promoters of genes that are upregulated after treatment. In summary, although NKL54 cannot outcompete MEF2 from binding to class IIa HDACs, it supports MEF2-dependent transcription through several actions, including potentiation of chromatin binding.
“…Unfortunately, patients often relapse and available cytotoxic therapies show only modest clinical activity [ 13 , 14 ]. We have recently shown that uterine LMS cells are sensitive to proteotoxic stress-induced apoptosis, whereas normal human uterine smooth muscle cells (HUtSMC) are more resistant [ 5 ]. To understand the molecular basis of this resistance, we monitored transcriptional adaptations to proteotoxic stress in cancer and normal cells.…”
Section: Resultsmentioning
confidence: 99%
“…Compared to LMS cells (SK-UT-1), immortalized HUtSMC-hTERT are partially resistant to cell death induced by 2c (Fig. 1A ), like primary HUtSMC [ 5 ]. Fig.…”
Section: Resultsmentioning
confidence: 99%
“…The induction of proteotoxic stress is a relatively new therapeutic strategy that has attracted considerable interest [ 5 , 7 , 8 , 30 – 32 ]. In this manuscript, we addressed two important issues: (i) understanding the reasons for the differential susceptibility of normal cells to proteotoxic stress compared to cancer cells and (ii) the possibility of enhancing the cell death response triggered by proteotoxic stress.…”
Section: Discussionmentioning
confidence: 99%
“…All cellular efforts are aimed at overcoming proteotoxic stress. If it is not overcome, cell death by apoptosis is a possible option [ 4 , 5 ].…”
Leiomyosarcoma (LMS) is aggressive cancer with few therapeutic options. LMS cells are more sensitive to proteotoxic stress compared to normal smooth muscle cells. We used small compound 2c to induce proteotoxic stress and compare the transcriptomic adaptations of immortalized human uterine smooth muscle cells (HUtSMC) and LMS cells SK-UT-1. We found that the expression of the heat shock proteins (HSPs) gene family is upregulated with higher efficiency in normal cells. In contrast, the upregulation of BH3-only proteins is higher in LMS cells. HSF1, the master regulator of HSP transcription, is sequestered into transcriptionally incompetent nuclear foci only in LMS cells, which explains the lower HSP upregulation. We also found that several compounds can enhance the cell death response to proteotoxic stress. Specifically, when low doses were used, an inhibitor of salt-inducible kinases (SIKs) and the inhibitor of IRE1α, a key element of the unfolded protein response (UPR), support proteotoxic-induced cell death with strength in LMS cells and without effects on the survival of normal cells. Overall, our data provide an explanation for the higher susceptibility of LMS cells to proteotoxic stress and suggest a potential option for co-treatment strategies.
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