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Advanced Neurology TRPM7 signaling in glioblastoma

from our migration assay showed that CsA significantly the next steps should involve genetic manipulation of
decreased U251 cell migration, and naltriben alone had the calcineurin levels by employing techniques such as RNA
opposite effect (Figure 4A-D). However, CsA and naltriben interference. In summary, calcineurin is a downstream
co-treatment significantly reduced migration compared to player in the TRPM7-mediated signaling pathway that
the naltriben-only group, and not significantly different regulates GBM cell function.
compared to the CsA-only group. Similar trends were found
in the rate of cell invasion (Figure 4E), and phosphorylation 5. Conclusion
levels of AKT and ERK (Figure 5). Taken together, CsA The present findings provide evidence that the transient
treatment appears to occlude the potentiating effect of receptor potential melastatin 7 (TRPM7) channel interacts
naltriben on GBM cell function, thereby suggesting that with calcineurin A-subunit proteins, either directly or
calcineurin acts downstream of TRPM7. To strengthen indirectly. Aberrant TRPM7 activity can upregulate GBM
this finding, future studies can simultaneously investigate if cell function through various pathways, and calcineurin
pharmacological TRPM7 inhibition, such as with the use of is potentially one of its downstream targets (Figure 6). In
carvacrol or waixenicin A [15,16] , has similar effects on GBM this study, we employed one GBM cell line (i.e., U251) to
cell function as pharmacological inhibition of calcineurin.
In addition, 24-h CsA treatment increased TRPM7 elucidate the proposed mechanism. It is important to note
mRNA and protein levels in U251 cells (Figure 3B-D). that the present findings with the U251 cell line may not
One possible explanation is that reduction of calcineurin necessarily reflect the nature of TRPM7-mediated signaling
activity due to CsA-mediated inhibition may stimulate the in glioma stem cells. Moving forward, future studies should
cell to synthesize excess TRPM7 protein as compensation consider confirming the interaction between TRPM7 and
for the loss of downstream calcineurin-related signaling. calcineurin using other GBM cell lines as well as glioma
Overall, our results suggested that TRPM7 may function stem cells. By identifying potential drug targets within the
as an upstream regulator of calcineurin activity in GBM. TRPM7-mediated signaling pathway, the ultimate goal is
to advance the development of novel chemotherapeutic
Since the activation of the MEK/ERK pathway is involved agents for the treatment of GBM.
in GBM invasiveness, migration, and death resistance [35,36] ,
the decreasing trend in p-ERK level following CsA Acknowledgments
treatment was expected (Figure 5E). However, in contrast
[20]
with a previous report , higher p-ERK levels following We would like to thank Haorui Zhang, Neruja Loganathan,
naltriben treatment were not observed. This may be due and Andy Tran for their technical assistance.
to the lower dosage (i.e., 25 µM instead of 50 µM) used Funding
in the present experiments to preserve cell viability in the
naltriben and CsA co-treatment group. Furthermore, we This work was supported by the following grants: Canadian
employed a different GBM cell line from this previous Institutes of Health Research (CIHR PJT-153155) to ZPF;
study (i.e., U251 instead of U87), suggesting potential cell Natural Sciences and Engineering Research Council of
line-dependent effects . Nevertheless, the co-treatment Canada (NSERC) Discovery Grants (RGPIN-2016-04574)
[20]
group showed a decreasing trend in p-ERK levels, similar to HSS.
to the CsA-only group, and trended towards reduction
when compared to control or naltriben groups. These Conflict of interest
results were consistent with our migration and invasion The authors declare that they have no conflicts of interest
assay findings. Interestingly, p-AKT levels in U251 cells with the contents of this article.
were significantly elevated with CsA treatment, consistent
with previous reports in other cell types, where it has been Author contributions
rationalized that the loss of dephosphorylating activity
due to calcineurin inhibition would lead to higher p-AKT Conceptualization: Zhong-Ping Feng, Hong-Shuo Sun
levels [24,26] . However, the literature shows that the activation Formal analysis: All authors
of the PI3K/AKT pathway promotes GBM proliferation Investigation: Haifan Gong
and tumor invasion, and inhibiting TRPM7 decreases Writing – original draft: Haifan Gong, Raymond Wong,
the p-AKT level [16,37] . One possible explanation is that any Julia Bandura
potential GBM-enhancing effects due to CsA-mediated Writing – review & editing: All authors
upregulation of p-AKT are outweighed by the collective Ethics approval and consent to participate
inhibitory effects of CsA on other mechanisms involved
in GBM cell function. To build on our present findings, Not applicable.

Volume 2 Issue 3 (2023) 8 https://doi.org/10.36922/an.334