The role of nuclear mechano-transduction in regulating gene expression and shaping the spatial landscape in glioblastoma

Glioblastoma (GBM) is the most common malignant primary brain tumor, with a median survival of 12-15
months. Despite surgical resection and adjuvant therapy, the tumor inevitably recurs. GBM transcriptional
states, which are diverse and driven by distinct gene expression programs, are critical determinants of the
response to therapy and prognosis. To find new treatments to block GBM progression, we need a better
understanding of gene expression regulation which underlies the diverse transcriptional states in GBM. In the
proposed work, we will investigate how physical force regulates GBM transcriptional states, which is an
understudied area of gene expression regulation in GBM. Physical force in the form of tissue stiffness is
transmitted from the cytoplasm to the nucleus and leads to changes in gene expression, among other biological
effects, in a process called nuclear mechano-transduction (NMT). We found that the level of Lamin A/C, a key
structural component of the nuclear lamina, controls the threshold for NMT. Our overarching hypothesis is that
changing NMT will alter GBM transcriptional states and GBM progression. Several facts support our hypothesis:
1- GBM cells exhibit significant nuclear membrane irregularities, which is a sign of abnormal force transmission
on the nucleus. 2- Specific GBM transcriptional states are differentially spatially localized across anatomic
locations with varying degrees of tissue stiffness – and thereby force transmitted onto GBM nuclei. And 3- The
Astrocyte-like/mesenchymal GBM transcriptional state, which is associated with treatment resistance, can be
induced by signaling via hippo (YAP1) signaling, which can be activated by NMT. The goal of the study is to
dissect the roles of NMT in GBM gene expression and prognosis. In aim #1, we will leverage the diverse landscape
of tissue stiffness in the infiltrated human brain, including the GBM core and periphery, to define the correlation
between NMT and GBM transcriptional states. We will further use mouse xenograft models of de-identified
patient-derived GBM cell lines to quantify the effects of tissue anatomy – and thereby stiffness – on GBM
transcriptional states. In aim #2, we will control NMT levels in human GBM cell lines by increasing or decreasing
Lamin A/C and measure the changes in GBM transcriptional states across the landscape of the infiltrated brain
in mouse xenografts GBM models. Using LMNA mutants that do not increase NMT, we will control for the NMT-
independent effects of Lamin A/C on gene expression. A dominant-negative KASH construct that abolishes NMT
will serve as a negative control. We will monitor the activity of NMT using a YAP1 reporter and measure the
changes in animal survival, and multiple transcriptional and histopathologic readouts of tumor progression. This
study will open a new avenue of investigation into the gene expression regulation in GBM and identify novel
mechanisms that can guide the development of therapeutic strategies against GBM.

Grant Number: 1R21NS136647-01A1
NIH Institute/Center: NIH
Principal Investigator: Osama Al Dalahmah