In summary, we have discovered micropeptide hSPAR as an intrinsic metabolism regulator that integrates three critical pathways—cellular glutamine-level control, P27KIP1 protein stability, and noncanonical lysosomal-translocation of P27KIP1—to generate a robust inhibitory effect on mTOR signaling and cancer cell proliferation. The gene discussed is CDKN1B; the disease is cancer.