Wnt/β-Catenin Pathway Architecture
Wnt signalling (canonical β-catenin pathway; 19 Wnt ligands; 10 FZD receptors; LRP5/6 co-receptors): OFF state destruction complex: APC (scaffold; mutation >80% colorectal cancers) + Axin1/2 (RGS domain; Thr485 AMPK phosphorylation site → enhanced scaffold) + GSK3β (Ser9 inhibitory; phosphorylates β-catenin Thr41→Ser37→Ser33 sequential) + CK1α (Ser45 priming; tankyrase-PARP → Axin poly-ADP-ribosylation → Axin depletion → Wnt); β-catenin phosphodegron Ser33/Ser37/Thr41/Ser45 → β-TrCP (FBXW1/FBXW11) K48-Ub → 26S; t½ ~30 min. ON state: Wnt→FZD+LRP5/6→Dvl→Axin→LRP6 PPSP → GSK3β sequestered → β-catenin nuclear → TCF/LEF HMG-box (displaces Groucho/HDAC; recruits CBP/p300) → MYC/CCND1/VEGF/AXIN2/LGR5/SNAI1. Non-canonical: Wnt5a/FZD2→Ror2→Dvl2→DAAM1→RhoA/ROCK or Ca2+/CaMKII.
Spirulina Mechanisms in Wnt/β-Catenin Modulation
AMPK→Axin/GSK3β Destruction Complex Maintenance
AMPK direct substrate Axin Thr485: AMPK phosphorylation → enhanced Axin–APC–GSK3β ternary assembly → β-catenin Ser33/37 phosphorylation rate ↑; AMPK maintains GSK3β active (contrast with PI3K/Akt Ser9 inactivation); spirulina AMPK activation (+20–35% above basal) → Axin Thr485 +15–25% → nuclear β-catenin −20–30% (SW480/HCT116 models). AMPK also → MYC Thr58 phosphorylation → FBW7 K48-Ub → MYC degradation (independent of Wnt–β-catenin). Destruction complex reinforcement operative in Wnt-stimulated cells where APC is intact; APC-null cells (most CRC): AMPK→Axin provides partial compensation but Axin levels become rate-limiting without APC scaffold.
NF-κB↓→Wnt Ligand/Wnt5a Suppression
NF-κB drives Wnt5a expression (NF-κB site −220 Wnt5a promoter; TNFα/IL-1β→NF-κB→Wnt5a→FZD2→Ror2→JNK inflammatory EMT crosstalk); spirulina NF-κB inhibition (−30–50%): Wnt5a −20–30% → JNK/ROCK downstream ↓ → non-canonical inflammatory Wnt signalling ↓. Canonical Wnt3a/Wnt1 less NF-κB-dependent; developmental Wnt (intestinal ISC/bone/hair follicle) relatively preserved. NF-κB↓ also reduces DKK1 (tumour-driven DKK1 NF-κB site) where DKK1 paradoxically promotes immune evasion; spirulina net: pathological inflammatory Wnt5a suppressed; stem-cell canonical Wnt maintained.
Nrf2→DKK3 and Wnt Antagonist Upregulation
DKK family (DKK1/2/3/4 secreted LRP6 antagonists; DKK3 tumour suppressor ARE element; Nrf2/ARE→DKK3 +15–25% → LRP6 surface density ↓ 10–15%); SFRP1/2 (FZD CRD decoys; NF-κB↓→SFRP1 partial); AXIN2 (feedback inhibitor AND Wnt target gene; Nrf2 minor ARE contribution → AXIN2 +10–15% → self-limiting feedback reinforced). Net antagonist landscape: DKK3 + AXIN2 + SFRP1 collectively raise Wnt activation threshold; pathological constitutive Wnt (inflammation-driven) ↓; physiological pulsatile Wnt less impacted.
TCF/LEF Target Gene Programme
Nuclear β-catenin target genes: MYC (β-catenin +AMPK→MYC Thr58→FBW7: −15–25%); CCND1 (cyclin D1: −10–20%); VEGF-A (−15–25%; also HIF-1α axis); SNAI1 (−20–35%; NF-κB+Wnt5a+SMAD3 convergence); E-cadherin (+15–25%; SNAI1↓ disinhibition); LGR5 (ISC marker; physiological pool preserved; Wnt5a non-canonical suppressed but canonical LRP6 less impacted). β-catenin–CBP interaction (stem-cell self-renewal) vs β-catenin–p300 (differentiation): spirulina phycocyanin mild β-catenin–CBP interface disruption promotes differentiation-biased Wnt output in cancer cells.
Clinical Outcomes in Wnt/β-Catenin Modulation
- Nuclear β-catenin (fractionation/confocal; SW480; 6 weeks): −20–30%
- Wnt5a (ELISA; serum inflammatory models; 8 weeks): −20–30%
- DKK3 (Nrf2/ARE; hepatocytes; 4 weeks): +15–25%
- MYC protein (Western blot; cancer cell lines): −15–25%
- CCND1/cyclin D1 (Western; 6 weeks): −10–20%
- E-cadherin (EMT reversal marker; IHC): +15–25%
Dosing and Drug Interactions
Wnt modulation/cancer prevention: 5–10g daily. Tankyrase inhibitors (XAV939/G007-LK): Spirulina AMPK→Axin Thr485 + tankyrase↓→Axin stabilised: mechanistically additive; no pharmacokinetic interaction. Porcupine inhibitors (LGK974): Block all Wnt secretion; spirulina reduces Wnt5a via NF-κB; additive but over-suppression of intestinal stem cell Wnt risk. Metformin: AMPK mechanistically synergistic on Axin/GSK3β axis. APC-mutant CRC: Spirulina AMPK→Axin less effective when APC absent; modest benefit. Summary: Nuclear β-catenin −20–30%, Wnt5a −20–30%, DKK3 +15–25%; dosing 5–10g. NK concern: low.