Increased placenta growth factor mRNA level is significantly associated with progression, recurrence and poor prognosis of oral squamous cell carcinoma

Background/Purpose: Expression of placenta growth factor (PlGF) mRNA is shown to correlate with the progression and prognosis of several human cancers. In this study, we assessed whether the PlGF mRNA level in oral squamous cell carcinoma (OSCC) tissue could be used to predict the progression and prognosis of OSCCs in Taiwan. Methods: This study used quantitative real-time reverse transcription-polymerase chain reaction (quantitative RT-PCR) to detect the PlGF mRNA levels in 63 paired OSCC and adjacent normal-looking oral mucosa (non-OSCC) tissues. Threshold cycle (C_T) was defined as the PCR cycle number needed to generate a pre-determined amount of DNA (threshold). For a chosen threshold, a smaller starting copy number of mRNA results in a higher C_T value. In this study, the relative expression level of tissue PlGF mRNA in each OSCC patients was expressed as -ΔC_T = -(OSCC C_T - non-OSCC C_T). Thus, the higher the -ΔC_T, the greater the copy number of PlGF mRNA in tissues. Results: We found that the higher mean PlGF mRNA -ΔC_T value was significantly associated with OSCCs with larger tumor size (p = 0.03), positive lymph node metastasis (p = 0.003), more advanced clinical stages (p = 0.013) or the presence of loco-regional recurrence (p = 0.039). Positive lymph node metastasis (p = 0.019) and PlGF mRNA -ΔC_T value >2 (p = 0.016) were identified as two independent unfavorable prognosis factors by multivariate analyses with Cox regression model. Moreover, Kaplan-Meier curve showed that OSCC patients with a PlGF mRNA -ΔC_T value >2 had a significantly poorer recurrence-free survival than those with a PlGF mRNA -ΔC_T value ≤2 (log-rank test, p = 0.017). Conclusion: The OSCC tissue PlGF mRNA level can be used to predict the progression and prognosis of OSCCs in Taiwan.