The Correlation Between The Biomarkers Of PI3K/AKT/mTOR Signaling Pathway And Effects Of The Second Line Anti-HER2 Therapy In Metastatic Breast Cancer

ObjectiveThe activation of PI3K/AKT/m TOR pathway is one of the possible mechanisms leading to the Trastuzumab resistance in HER2-positive metastatic breast cancer. Both domestic and international guidelines recommend lapatinib plus capecitabine as an effective treatment to patients of HER2-positive metastatic breast cancer with failure in anthracyclins, taxane and resistance to Trastuzumab. This study focused on those patients mentioned above. Firstly, we observed the clinical efficacy of subsequent lapatinib-based therapy. Then we further explored the indexes related to the efficacy of lapatinib after failure in Trastuzumab in HER2-positive MBC, including the biomarkers of PI3K/AKT/m TOR pathway, the activation or not of the whole signaling pathway and the patients’ clinical and pathological characteristics. That is to distinguish the lapatinib-sensitive from lapatinib-resisted patients in HER2-positive metastatic breast cancer with resistance to Trastuzumab and to optimize the individual treatment of HER2-positive breast cancer. Methods60 matched patients were enrolled from the breast department of the Affiliated Hospital of Academic of Military Medical Science. All of the patients are HER2-positive MBC with failure in anthracyclins, taxane and resistance to Trastuzumab. Their clinical benefit rate(CBR), objective response rate(ORR) and progression free survival(PFS) were adopted as indexes of clinical efficacy. We collected the clinical and pathological characteristics of patients. Response Evaluation Criteria in Solid Tumors(RECIST1.1) was used to evaluate the efficacy, Common Terminology Criteria for Adverse Events version(CTCAE)3.0 was used to evaluate the adverse reactions, treatment after the Trastuzumab-resistance was given according to c NCCN( Lapatinib(1250 mg/d, oral) plus capecitabine(2000 mg/m2/d; oral; on days 1–14) in a 21-d cycle.). Immunohistochemical(IHC) test of tissue specimens of metastatic lesions were applied to determine the status of biomarkers of PI3K/AKT/m TOR singaling pathway(PTEN、PIK3CA、p-Akt、p-4EBP1).Two experienced pathologists were advised to interpret the results. Chi square test, univariate and multivariate logistic regression analysis were used to investigate the correlation ofthe biomarkers of PI3K/AKT/m TOR pathway, the activation or not of the single pathway, and patients’ clinical and pathological characteristics with the clinical efficacy. Analyses were using SPSS19.0 statistical software. Results1. The median age was 45(28-67) year-old. All of the enrolled patients were HER2 positive, 57% patients were hormone receptor negative(ER and PR are both negative), the median number of metastatic sites was 3; the median number of rescued therapy was 3 line. The efficacy of lapatinib-based treatment of all patients was also evaluated: The median progression-free survival(PFS) was 4.6 months(95% CI 3.8-5.4 months); clinical benefit rate(CBR) was 50.0%; Objective response rate(ORR) was 36.7%.2. Tissue specimens of metastatic lesions before the regimen of lapatinib from 60 cases were made IHC test to determine the status of PTEN(n=60), PIK3CA(n=60), pAKT(n=34) and p-4EBP1(n=50). The percentage of positive cells was counted in tumor cells. The results show that the positive expression ratio of PTEN, PIK3 CA, pAKT, p-4EBP1 was 50.0%, 30.0%, 41.2%, 26.0%, respectively. The ratio of PI3 K pathway activation(defined as PIK3 CA positive and/or PTEN Loss according to the previously reported) was 63.3%(38/60) and the ratio of PI3K/AKT pathway activation(defined as PI3 K pathway activation plus p-AKT positive) was 17.6%(6/34).3. The correlation of the biomarker of PI3K/AKT/m TOR pathway, the activation or not of signaling pathway, and the patients’ clinical and pathological characteristics with the efficacy of lapatinib was analyzed. Univariate analysis revealed that: compared with PTEN expression group, PTEN loss patients had significant shorter median PFS(4.2 VS 6.3 months, p=0.015) and lower CBR(33.3% VS 70.0%, p=0.004); compared with p-AKT negative group, p-AKT positive had significant shorter median PFS(2.0 VS 4.6 months, p=0.03) and lower ORR(14.3% VS 50.0%, p=0.03); compared with PI3 K pathway non-activated group, patients with PI3 K pathway activated had significant shorter median PFS(4.3 VS 6.5 months, p=0.015) and lower CBR(36.8% VS 77.3%, p=0.003); compared with PI3K/AKT pathway non-activated group, patients with PI3K/AKT pathway activated had more shorter median PFS(2.0 VS 4.4 months, p=0.013). Additionally, all of the 6 patients whose PI3K/AKT pathway were activated didn’t produce clinical benefit; compared with the clinical characteristic of non-liver metastases, patients with liver metastases had significant shorter median PFS(3.2 VS 5.4 months, p=0.02); patients with PIK3 CA positive(p=0.051) and p-4EBP1 positive(p=0.19) showed shorter median PFS, but without significant difference. Multivariate analysis revealed that the risk of disease progression for patients with PTEN loss was more than the risk for patients with PTEN expression(HR=0.45, 95% CI, 0.26–0.78, P = 0.005); the risk of disease progression for patients with p-AKT positive was more than the risk for patients with p-AKT negative(HR=2.87, 95% CI, 1.32–6.25, P = 0.008); the risk of disease progression for patients with PI3 K pathway activation was higher than the risk for patients with PI3 K pathway non-activated(HR=2.28, 95% CI, 1.28–4.07, P = 0.005); the risk of disease progression for patients with PI3K/AKT pathway activation was higher than the risk for patients with PI3K/AKT pathway non-activated(HR=3.26, 95% CI, 1.20–8.87, P = 0.021); the risk of disease progression for patients with liver metastasis was higher than the risk for patients with non-liver metastasis(HR=2.19, 95% CI, 1.26–3.82, P = 0.006). As a consequence, those results mean that PTEN loss, p-AKT positive, PI3 K pathway activation, PI3K/AKT pathway activation and liver metastasis were five independent prognostic factors of subsequent lapatinib therapy. Conclusion1.HER2-positive MBC patients with trastuzumab-resistance in the first line antiHER2 therapy could benefit from the second line lapatinib-based regimen.2. The status of HER2 alone cannot predict efficacy of anti-HER2 targeted regimen, indicating thatnot all of the HER2 positive patients with trastuzumab-resistance could benefit from the targeted replacement therapy. Tissue specimens of metastatic lesions before lapatinib-based therapy with PTEN Loss, p-AKT positive, PI3 K pathway activation, PI3K/AKT pathway activation and patients with liver metastasis were potential indication of prognosis of subsequent lapatinib therapy.3. Combined detection of PTEN, PI3 K and AKT can provide guidance on how to determine and overcome drug-targetting resistance. Which biomarker(s) of PI3K/AKT/m TOR pathway have direct correlation with the efficacy of lapatinib regimen was still unclear. Considering that there are many alternative signaling pathways and complex feedback regulation mechanism, further study is needed to optimize individual treatment of HER2-positive breast cancer.