A research article in the March 2015 issue of the JCI identifies a crosstalk mechanism by which lung tumor cells become more metastatic via alteration of the chemical nature of the collagen crosslinks in the tumor stroma. Using a combination of human tumors and mouse models, including models of non-metastatic lung adenocarcinomas and of metastatic lung tumors, the authors show that tumor cells expressing lysyl hydroxylase 2 (LH2) make hydroxylysine aldehyde–derived collagen crosslinks that are more stable, creating a firmer stroma. In addition, they show that LH2 expression, which is a marker of poor prognosis, is regulated via STAT3-HIF-1α heterodimers induced by other secreted factors from cancer-associated fibroblasts. We interviewed Yulong Chen and his collaborator Masahiko Terajima about this work.
Can you tell us about your backgrounds and what made you interested in cancer research?
Yulong Chen: My background is in clinical medicine; however, during my medical school training in China, we were exposed to laboratory research. Through these hands-on lab experiments, I realized the excitement of research — doing experiments that nobody has ever done before and being the first to know the result is incredibly exciting. I felt that while being a doctor would allow me to treat patients individually, I would have greater impact on many patients by performing research. So after I graduated from Fudan University, I worked for three years at Ruijin Hospital, which is part of the Shanghai Institute for Hematology, where I studied leukemias and developed my bench research skills. At this point, I realized I would need an advanced degree in biomedical sciences, so I applied to the Ph.D. program in Cancer Biology at the University of Texas MD Anderson Cancer Center, where I worked in lung cancer. I remained interested in lung cancer biology, so after graduating, I joined Dr Kurie’s lab, where I began this research and was able to meet Masahiko. My wife is also a postdoctoral fellow in genetic epidemiology, so Houston was an ideal place for us both to advance our careers.
Masahiko Terajima: Similar to Yulong, I came from a clinical background as well; however, my clinical degree was in dentistry. After I obtained my D.D.S., I began my research and dental practice in the Orthodontic Department at the University of Japan. My research interests were in orthodontic treatment of patients who have congenital diseases that impact their mouth — for example, cleft lip or palate, or bone diseases. I treated these patients as an orthodontist and conducted clinical research using computed tomography and magnetic resonance imaging to investigate the 3D maxillofacial morphologies in these patients who had jaw deformities. During this time I became intensely interested in bone biology. I was fortunate to find a great mentor, Dr. Yamauchi, when I came to North Carolina 6 years ago to start my research in collagen biochemistry and developed methods for quantifying the types of collagen crosslinks and other post-translational modifications. My contribution to this work was to use these methods to describe the collagen structures and stability in mouse models under various conditions.
Dr. Chen, it is very interesting that you decided to stay at the same institution for both your graduate training and your postdoc. Some discourage this, saying that it limits your training. Do you have any advice regarding this choice?
Chen: I decided to stay because MD Anderson is a great place to train. In my graduate work in Dr. Reuben Lotan’s lab, I studied the role of the GPRC5A tumor suppressor and its regulation of STAT3 in mouse models of lung cancer. During the last year of my PhD, my mentor introduced me to Dr. Kurie. After talking to him, I became interested in his research, and he had some ongoing projects with substantial overlap with my background. I also realized these models had several advantages in terms of clinical relevance. Unfortunately, the models I worked on in graduate school were non-metastatic; however, the majority of lung cancer patients develop metastases, which cause most of the mortality. Dr. Kurie’s models develop metastatic tumors, and we felt that I would be able to apply the skills I learned in my graduate work to characterize these models mechanistically and derive novel insights into lung cancer pathogenesis. I am lucky that my transition was straightforward, and I have been happy in my postdoctoral lab since 2010. If you have a passion for a research area and find a great mentor in your own institution or even within the same department, I do not think it is a negative factor for your training if you are learning new things and being productive.
How have you both collaborated on this project, and what have you learned about productive collaborations?
Chen: We began the collaboration partway through the project. We had identified the gene that codes for LH2, which is known to modify collagen, and observed that when we inhibited it in lung tumor models, we decreased metastasis. Conversely, when we overexpressed it, we increased the metastatic capability of tumor cells. Our lab has experience with tumor models and cell biology experiments, but we lacked the biochemical tools to study collagen biology. We were very lucky to find Dr. Yamauchi and Masahiko to help with this aspect.
Terajima: Yes, from the first time Dr. Yamauchi mentioned this collaboration, I was very excited about this project, as it had direct impact on human health, especially cancer metastasis. Until then, my research was focused on collagen post-translational modifications in bone/osteoblast biology. It was an eye-opening experience to know that these modifications are involved in cancer metastasis. I was also very happy to be able to collaborate with a great cancer research group at MD Anderson. Our collaboration with Dr. Kurie and Yulong has been very smooth and fruitful due to the good communication within the team and sharing of knowledge throughout the project.
Chen: You will also note from the author list we had many other collaborators, a total of 27 coauthors, including surgeons from Methodist Hospital here in the Texas Medical Center who provided us with the lung tissue samples and paired normal tissues. This contribution was important, too, in demonstrating the human relevance of our mouse model discoveries. We had statistical help from Dr. Chad Creighton of Baylor College of Medicine to analyze the microarray data, and assistance from lung pathologists Dr. Ignacio Wistuba and Dr. Jaime Rodriguez, who stained the tissues. Truly, all of our coauthors on the paper made valuable contributions that I appreciate very much. Some of these collaborations, especially with Masahiko, are ongoing based on continued interest in the new directions of our research.
I have to credit the leadership of my mentor, Dr. Kurie, for the overall success of this collaborative project. I admire the fact that even though he is a busy medical oncologist, he remains very accessible to facilitate moving projects forward. In addition, being at MD Anderson gives us access to many core facilities, such as molecular biology and state-of-the-art microscopy resources.
How do you see this research being applied in the future?
Terajima: Our work strongly suggests that collagen crosslinking is important in lung cancer metastasis and LH2 is an important structural regulator of collagen. It is possible that local delivery of specific LH2 inhibitors could be developed as therapeutic options to inhibit metastasis.
Chen: Our laboratory is interested in a screen for LH2 inhibitors. There are no known commercially available inhibitors. We have recently started a new collaboration with a laboratory at University of Texas at Austin. First, we will need to develop a high-throughput assay to measure LH2 activity so that compound libraries can be screened for functionality. This work is still at the very earliest stage, but we are very excited about potentially finding some hits and evaluating them in our preclinical models.
What other research directions has this work uncovered that you are excited about?
Chen: I think one of the important directions that we will take is getting an understanding of other enzymes that might regulate collagen in the tumor microenvironment. It is known that collagen is heavily prone to post-translational modifications such as hydroxylation and glycosylation, but the players in this pathway are not all well understood.
Are there any limitations to applying this approach to inhibiting metastasis in other tumor types?
Chen: Yes certainly, it would be prudent not to rush to conclusions that this will be a universal antimetastatic approach. Different tumor types that derive from different tissues may have different phenotypes upon LH2 inhibition. It will be necessary to test this approach in each tumor type that expresses LH2 to know whether to pursue this further beyond lung cancer. There are other examples of genes that are tumor suppressors in some models and oncogenes in others. Lots of work ahead of us!
About the First and Second Authors
Yulong Chen, M.D./Ph.D, is currently a postdoctoral fellow in Dr. Jonathan Kurie’s laboratory at the University of Texas MD Anderson Cancer Center. He trained as a medical doctor at Fudan University in China, prior to attending graduate school at the University of Texas Health Science Center at Houston (UTHSC)/MD Anderson Cancer Center, where he obtained his Ph.D. in cancer biology. His research has been focused on lung cancer biology and metastatic mechanisms, and his plan is to continue working toward an academic research professorship.
Masahiko Terajima, D.D.S./Ph.D., is currently a postdoctoral fellow in Dr. Mitsuo Yamauchi’s laboratory at the University of North Carolina at Chapel Hill. Prior to coming to the United States from Japan, he obtained his dental degree and a certificate in orthodontics. He worked as an orthodontist while doing clinical research in Japan. His research interests now focus on the biological significance of collagen post-translational modifications, including lysine hydroxylation, glycosylation, and cross-linking in connective tissue.
About the interviewers
Freddy T. Nguyen is an M.D./Ph.D. candidate at the University of Illinois at Urbana-Champaign. He is the founder of the American Physician Scientists Association and served on the Associate Member Council of the American Association for Cancer Research. His research interests currently lie at the intersection of biomedical optics and cancer research. He received his B.S. in chemistry and B.A. in mathematics from Rice University.
Angela Alexander, Ph.D., is a TRIUMPH (Translational Research in Multi-Disciplinary Program) postdoctoral fellow at the University of Texas MD Anderson Cancer Center, where she works in molecular therapeutics. Her translational research interests include cell cycle/mitotic targets in aggressive cancers, including triple-negative and inflammatory breast cancers, and biomarker development for clinical trials based on her work. She obtained her Ph.D. in molecular carcinogenesis from UTHSC/MD Anderson Cancer Center and her B.S. in finance from the University of Delaware. Previously, she served on the Associate Member Council of the American Association for Cancer Research, and she now volunteers for the IBC Network Foundation in an educational/advocacy capacity.
Epithelial tumor metastasis is preceded by an accumulation of collagen cross-links that heighten stromal stiffness and stimulate the invasive properties of tumor cells. However, the biochemical nature of collagen cross-links in cancer is still unclear. Here, we postulated that epithelial tumorigenesis is accompanied by changes in the biochemical type of collagen cross-links. Utilizing resected human lung cancer tissues and a p21CIP1/WAF1-deficient, K-rasG12D-expressing murine metastatic lung cancer model, we showed that, relative to normal lung tissues, tumor stroma contains higher levels of hydroxylysine aldehyde–derived collagen cross-links (HLCCs) and lower levels of lysine aldehyde–derived cross-links (LCCs), which are the predominant types of collagen cross-links in skeletal tissues and soft tissues, respectively. Gain- and loss-of-function studies in tumor cells showed that lysyl hydroxylase 2 (LH2), which hydroxylates telopeptidyl lysine residues on collagen, shifted the tumor stroma toward a high-HLCC, low-LCC state, increased tumor stiffness, and enhanced tumor cell invasion and metastasis. Together, our data indicate that LH2 enhances the metastatic properties of tumor cells and functions as a regulatory switch that controls the relative abundance of biochemically distinct types of collagen cross-links in the tumor stroma.
Yulong Chen, Masahiko Terajima, Yanan Yang, Li Sun, Young-Ho Ahn, Daniela Pankova, Daniel S. Puperi, Takeshi Watanabe, Min P. Kim, Shanda H. Blackmon, Jaime Rodriguez, Hui Liu, Carmen Behrens, Ignacio I. Wistuba, Rosalba Minelli, Kenneth L. Scott, Johannah Sanchez-Adams, Farshid Guilak, Debananda Pati, Nishan Thilaganathan, Alan R. Burns, Chad J. Creighton, Elisabeth D. Martinez, Tomasz Zal, K. Jane Grande-Allen, Mitsuo Yamauchi, Jonathan M. Kurie