55 research outputs found
Valproic Acid Synergizes With Cisplatin and Cetuximab in vitro and in vivo in Head and Neck Cancer by Targeting the Mechanisms of Resistance
Recurrent/metastatic head and neck squamous cell carcinoma (R/M HNSCC) is a
devastating malignancy with a poor prognosis. The combination of cisplatin (CDDP) plus
cetuximab (CX) is one of the standard first-line treatments in this disease. However, this
therapeutic regimen is often associated with high toxicity and resistance, suggesting that
new combinatorial strategies are needed to improve its therapeutic index. In our study,
we evaluated the antitumor effects of valproic acid (VPA), a well-known antiepileptic
agent with histone deacetylase inhibitory activity, in combination with CDDP/CX doublet
in head and neck squamous cell carcinoma (HNSCC) models. We demonstrated, in
HNSCC cell lines, but not in normal human fibroblasts, that simultaneous exposure to
equitoxic doses of VPA plus CDDP/CX resulted in a clear synergistic antiproliferative and
pro-apoptotic effects. The synergistic antitumor effect was confirmed in four different
3D-self-assembled spheroid models, suggesting the ability of the combined approach
to affect also the cancer stem cells compartment. Mechanistically, VPA enhanced
DNA damage in combination treatment by reducing the mRNA expression of ERCC
Excision Repair 1, a critical player in DNA repair, and by increasing CDDP intracellular
concentration via upregulation at transcriptional level of CDDP influx channel copper
transporter 1 and downregulation of the ATPAse ATP7B involved in CDDP-export.
Valproic acid also induced a dose-dependent downregulation of epidermal growth factor
receptor (EGFR) expression and of MAPK and AKT downstream signaling pathways
and prevent CDDP- and/or CX-induced EGFR nuclear translocation, a well-known
mechanism of resistance to chemotherapy. Indeed, VPA impaired the transcription
of genes induced by non-canonical activity of nuclear EGFR, such as cyclin D1 and thymidylate synthase. Finally, we confirmed the synergistic antitumor effect also
in vivo in both heterotopic and orthotopic models, demonstrating that the combined
treatment completely blocked HNSCC xenograft tumors growth in nude mice. Overall,
the introduction of a safe and generic drug such as VPA into the conventional treatment
for R/M HNSCC represents an innovative and feasible antitumor strategy that warrants
further clinical evaluation. A phase II clinical trial exploring the combination of VPA and
CDDP/CX in R/M HNSCC patients is currently ongoing in our institute
Crystal structure of the collagen triple helix model [(Pro-Pro-Gly)10]3
The first report of the full-length structure of the collagen-like polypeptide [(Pro-Pro-Gly)10]3 is given. This structure was obtained from crystals grown in a microgravity environment, which diffracted up to 1.3 â„«, using synchrotron radiation. The final model, which was refined to an Rfactor of 0.18, is the highest-resolution description of a collagen triple helix reported to date. This structure provides clues regarding a series of aspects related to collagen triple helix structure and assembly. The strict dependence of proline puckering on the position inside the Pro-Pro-Gly triplets and the correlation between backbone and side chain dihedral angles support the propensity-based mechanism of triple helix stabilization/destabilization induced by hydroxyproline. Furthermore, the analysis of [(Pro-Pro-Gly)10]3 packing, which is governed by electrostatic interactions, suggests that charges may act as locking features in the axial organization of triple helices in the collagen fibrils
Structural and functional analysis of aldolase B mutants related to hereditary fructose intolerance.
AlphaFold-Predicted Structures of KCTD Proteins Unravel Previously Undetected Relationships among the Members of the Family
One of the most striking features of KCTD proteins is their involvement in apparently unrelated yet fundamental physio-pathological processes. Unfortunately, comprehensive structure–function relationships for this protein family have been hampered by the scarcity of the structural data available. This scenario is rapidly changing due to the release of the protein three-dimensional models predicted by AlphaFold (AF). Here, we exploited the structural information contained in the AF database to gain insights into the relationships among the members of the KCTD family with the aim of facilitating the definition of the structural and molecular basis of key roles that these proteins play in many biological processes. The most important finding that emerged from this investigation is the discovery that, in addition to the BTB domain, the vast majority of these proteins also share a structurally similar domain in the C-terminal region despite the absence of general sequence similarities detectable in this region. Using this domain as reference, we generated a novel and comprehensive structure-based pseudo-phylogenetic tree that unraveled previously undetected similarities among the protein family. In particular, we generated a new clustering of the KCTD proteins that will represent a solid ground for interpreting their many functions
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