M. C. Hernandez1, L. Yang2, J. Leiting1, J. R. Bergquist1, M. J. Truty1 1Mayo Clinic,Department Of Surgery,Rochester, MN, USA 2Mayo Clinic,Center For Individualized Medicine,Rochester, MN, USA
Introduction:
Anal squamous cell carcinoma (ASCC) is an uncommon malignancy without substantial treatment advances. Current primary recommendations for non-metastatic ASCC include concurrent chemotherapy (5-FU) and radiation therapy. Metastatic disease is commonly treated with cisplatin-based chemotherapy with minimal evidence for other effective therapies given relative rarity of metastatic ASCC. Preclinical models to advance the treatment of anal cancers are limited to transgenic mice and cell lines. Patient derived xenografts models (PDX) allow for cancer tissue amplification that accurately recapitulates patient phenotype and these have been shown to correlate with clinical outcomes. We aimed to generate a preclinical PDX model of metastatic human ASCC and determine therapeutic sensitivities to correlate with in-vivo testing.
Methods:
PDX were generated from surgical resection of patient tumor tissue in NOD SCID mice. All patient and derived PDX tumors were histologically (H&E and IHC) confirmed. Time to tumor formation (TTF) and harvest (TTH) were recorded. Cell cultures were performed using a hanging drop and two dimensional methods and screened using cytotoxic therapies. Chemosensitivity was quantified using fluorescence intensity and direct cell counts. Secondarily, we performed live tissue sensitivity assays (LTSA), utilizing 200 um thick slices of PDX derived tumor tissue and screened using cytotoxic therapies. To corroborate ex-vivo sensitivities, in-vivo treatment studies using tumor bearing PDX models were performed. Unpaired Student’s t test was used to compare tumor volume response and p<0.05 was considered significant.
Results:
PDX was generated from an ASCC liver metastasis obtained at surgical resection with 100% engraftment rate in five mice. TTF and TTH were 13 and 55 days respectively. Three-dimensional (3D) cellular culture demonstrated marked sensitivity to combinatorial 5FU/oxaliplatin and 5FU/irinotecan. LTSA tumor tissue sensitivity correlated these findings as well. Formal in-vivo treatment using ASCC tumor bearing mice demonstrated significant tumor volume reduction and a cytotoxic response in those treated with combinatorial 5FU/oxaliplatin and 5FU/irinotecan compared to vehicle and 5FU alone.
Conclusion:
We have generated the first preclinical PDX model of metastatic ASCC that recapitulates the original patient tumor metastasis. Chemotherapy screening using 3D spheroids and LTSA demonstrated strong sensitivity to combinatorial therapies with 5FU. These screening data correlated well in tumor bearing PDX models. Different combinatorial chemotherapeutic regimens other than standard of care may provide meaningful response for patients with metastatic ASCC and may form the basis for future trials.
