OR2T6

OR2T6 is an olfactory-receptor-family gene that functions as a context-dependent regulator of tumor cell behavior, with opposing roles documented in breast and gastric cancer (PMID:31781505, PMID:41214150). In breast cancer cells, OR2T6 overexpression drives proliferation, invasion, migration, and epithelial-mesenchymal transition—upregulating Vimentin, N-cadherin, and β-catenin while reducing E-cadherin—and activates MAPK/ERK signaling (PMID:31781505). In gastric cancer, OR2T6 directly binds the calcineurin A subunit PPP3CA and stabilizes it via the ubiquitin-proteasome system, increasing PPP3CA protein levels and enzymatic activity (PMID:41214150); this stabilization is reinforced by OR2T6-driven calcium influx through a Gs/cAMP/PKA signaling axis (PMID:41214150). Through PPP3CA, OR2T6 suppresses AKT/mTOR signaling to inhibit proliferation and initiate autophagy (PMID:41214150), while concurrently promoting nuclear translocation of TFEB and transcriptional shutdown of lysosomal genes (LAMP1, MCOLN1, ATP6V1H, CTSB, CTSD), impairing lysosomal function and blocking autophagic flux (PMID:41214150). The structural basis of OR2T6 ligand recognition and how a single receptor produces opposite outcomes in different tissues have not been characterized in the available corpus.

1. 2019 Medium

   Established the first functional role for OR2T6 in cancer, showing it acts as a pro-tumorigenic driver of EMT in breast cancer rather than a silent olfactory receptor.

   Evidence Overexpression in MCF-7 and MDA-MB-231 with proliferation/invasion/migration assays and western blot for EMT markers

   PMID:31781505

   Open questions at the time

   • No mutagenesis or reconstitution to confirm receptor-intrinsic activity
   • No ligand or upstream activator identified
   • Mechanism linking OR2T6 to EMT markers not resolved beyond correlation
2. 2019 Medium

   Placed OR2T6's breast cancer activity within a defined signaling pathway by identifying MAPK/ERK activation as a downstream effector.

   Evidence Gene expression microarray plus western blot following OR2T6 manipulation in breast cancer cell lines

   PMID:31781505

   Open questions at the time

   • Direct coupling of the receptor to MAPK/ERK not demonstrated biochemically
   • Whether ERK activation is necessary for the EMT phenotype not tested
3. 2025 High

   Identified the first direct physical partner of OR2T6, the phosphatase PPP3CA, and a mechanism of action via ubiquitin-proteasome-dependent stabilization.

   Evidence Reciprocal Co-IP with mass spectrometry and ubiquitin-proteasome pathway and enzyme-activity assays in gastric cancer cells

   PMID:41214150

   Open questions at the time

   • Whether OR2T6 binds PPP3CA directly or through an adaptor not fully resolved
   • Identity of the ubiquitin ligase/deubiquitinase machinery involved unknown
   • Whether this interaction occurs in breast cancer not tested
4. 2025 Medium

   Connected canonical olfactory-receptor signaling output (Gs/cAMP/PKA) to PPP3CA regulation, linking receptor activity to calcium-dependent stabilization.

   Evidence Signaling pathway analysis with functional readouts in gastric cancer cells

   PMID:41214150

   Open questions at the time

   • Limited methodological detail for the Gs/cAMP/PKA axis
   • Calcium channel mediating influx not identified
   • Quantitative contribution of calcium versus proteasome to stabilization unclear
5. 2025 High

   Defined OR2T6 as a gastric cancer tumor suppressor acting through PPP3CA to dampen AKT/mTOR signaling and trigger autophagy, opposite to its breast cancer role.

   Evidence Loss- and gain-of-function studies in gastric cancer cell lines and in vivo, with AKT/mTOR western blots and autophagy assays

   PMID:41214150

   Open questions at the time

   • Molecular basis for the tissue-specific reversal of oncogenic/suppressive role unexplained
   • Whether PPP3CA phosphatase activity is required for AKT/mTOR suppression not isolated
6. 2025 Medium

   Resolved the apparent paradox of autophagy initiation without productive flux by showing OR2T6 drives TFEB nuclear translocation and lysosomal gene shutdown.

   Evidence TFEB localization, lysosomal target gene expression, and lysosomal function assays in gastric cancer cells

   PMID:41214150

   Open questions at the time

   • Mechanism by which TFEB nuclear translocation produces transcriptional inactivation rather than activation not explained
   • Link between PPP3CA/calcineurin activity and TFEB regulation not directly traced
   • Single lab without independent replication

• It remains unknown what ligand activates OR2T6 and what molecular switch determines whether it acts as an oncogene or tumor suppressor across tissues.
• No endogenous or synthetic OR2T6 ligand identified
• No structural model of the receptor or its PPP3CA interface
• Tissue-specific determinants of opposing phenotypes uncharacterized