Abstract A15: Humanized anti-hepatocyte growth factor (HGF) antibody, suppresses innate irinotecan resistance induced by fibroblast-derived HGF in colon cancer cells
Authors: Woo Jong Kyu , Kang Ju-Hee , Shin Keumju , Song Seong-Won , Kim Jung Ju , Lee Sang-Jin , Oh Seung Hyun 
Published: October 2015

Background and Purpose: Preclinical and clinical findings indicate that multiple tumor micro-environmental factors, including growth factors, protect solid tumors from therapeutic interventions. Experimental evidence has clarified some of the resistance mechanisms, which have led to the development of innovative approaches to treat cancer. Irinotecan is a semi-synthetic derivative of camptothecin, originally isolated from the Chinese/Tibetan ornamental tree Camptothecaacuminata. It is a key component of the first- and second-line treatment regimens for metastatic colorectal cancer (CRC). Study of irinotecan has demonstrated that its efficacy to treat cancer is superior to that of the best supportive care. However, de novo or acquired clinical resistance to camptothecins still exists expecting new target. The hepatocyte growth factor (HGF)/c-Met signaling system is known to be implicated in the development and progression of CRC, but the relationship between the expressions of HGF or c-MET and clinicopathologic feature remains controversial. We hypothesized that HGF from cancer-associated fibroblast (CAF) is related to innate irinotecan resistance. Therefore, HGF deprivation using neutralizing antibody is promising strategy to overcome irinotecan resistance induced by HGF in CRC.

Results: We postulated that innate drug resistance might be caused at least in part by factors secreted by the tumor stromal cells. We measured the levels of mRNA and secreted protein of HGF by real-time PCR and ELISA in fibroblast and CRC cell lines. The mRNA level of HGF was significantly higher in fibroblast than CRC cell lines. Also, secreted HGF was not detected in conditioned media (CM) from CRC cell, but was detected in CM from fibroblast. Fibroblast-conditioned media rescued CRC from irinotecan, indicating that the rescue was due to a factor secreted by the fibroblasts. We determined whether fibroblast derived HGF increases irinotecan resistance through MET-dependent pathway. Fibroblast-derived conditioned media led to activation of MET receptors in CRC. The siHGF transfection abrogated such MET activation. To test whether HGF directly contributes to the effect on enhancing irinotecan resistance in CRC, anti-HGF antibodies were added to the CM to neutralize the HGF activity. We found that anti-HGF antibodies suppressed irinotecan resistance. Taken together, our findings suggest that the fibroblast derived HGF may play a general role in cancer cell survival and targeting HGF may represent a novel strategy for the treatment of CRC. To examine the possible induction of irinotecan resistance by fibroblast derived HGF and the efficacy of combined treatment with humanized anti-HGF antibody and irinotecan in vivo, we generated xenograft in NOD/SCID mice inoculating HCT-116 human colon cancer cells subcutaneously with or without fibroblast. We found that the combination of irinotecan and humanized anti-HGF antibody induced marked suppression of tumor development. These results suggest that HGF produced by fibroblast induces irinotecan resistance, and that humanized anti-HGF antibody abrogates such resistance in vivo.

Conclusion: We identified HGF as an important determinant of resistance against irinotecan in CRC. Humanized anti-HGF antibody overcomes irinotecan resistance. These results demonstrate new options toward the early diagnosis of chemoresistance and suggest novel chemotherapy combining with anti-HGF antibody to prevent or significantly delay the onset of therapy resistance. These observations open new avenues toward the diagnosis of chemoresistance tumors and therapies targeting HGF over-expressing cancers.

Citation Format: Jong Kyu Woo, Ju-Hee Kang, Keumju Shin, Seong-Won Song, Jung Ju Kim, Sang-Jin Lee, Seung Hyun Oh. Humanized anti-hepatocyte growth factor (HGF) antibody, suppresses innate irinotecan resistance induced by fibroblast-derived HGF in colon cancer cells. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr A15.