Loss of tumor suppressor NF1 activates HSF1 to promote carcinogenesis

Area of Science:

• Oncology
• Molecular Biology
• Cellular Stress Response

Background:

• Tumor cells utilize intrinsic stress response pathways for adaptation and survival.
• The role of heat shock factor 1 (HSF1) in carcinogenesis, particularly in the context of tumor suppressor gene loss, is not well understood.

Purpose of the Study:

• To investigate the role of heat shock factor 1 (HSF1) in neurofibromatosis type 1 (NF1) deficiency-associated carcinogenesis.
• To elucidate the relationship between NF1 loss, MAPK signaling, and HSF1 activation in tumor development.

Main Methods:

• Utilized mouse embryonic fibroblasts (MEFs) with Nf1 gene deletion.
• Analyzed HSF1 activation, proteotoxic stress tolerance, and MAPK signaling pathways.
• Assessed the impact of Hsf1 deficiency on NF1-associated carcinogenesis in mouse models.
• Examined HSF1 expression and activation in human malignant peripheral nerve sheath tumor (MPNST) cell lines and patient samples.

Main Results:

• Loss of NF1 in MEFs led to increased HSF1 levels and activation, conferring tolerance to proteotoxic stress.
• HSF1 activation was dependent on and supported dysregulated MAPK signaling.
• Hsf1 deficiency suppressed NF1-associated carcinogenesis by attenuating RAS/MAPK signaling.
• HSF1 was overexpressed, activated, and essential for the viability of human MPNST cells and patient tumors.

Conclusions:

• NF1 deficiency unexpectedly activates HSF1, creating an addiction to this heat shock response regulator.
• This HSF1 activation is a conserved survival mechanism that facilitates carcinogenesis in NF1-deficient cancers.
• Targeting HSF1 may represent a therapeutic strategy for NF1-associated malignancies like MPNSTs.