Stromal-epithelial dynamics in response to fractionated radiotherapy

Qayyum, Muqeem

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https://hdl.handle.net/2142/42152 Copy

Description

Title

Stromal-epithelial dynamics in response to fractionated radiotherapy

Author(s)

Qayyum, Muqeem

Issue Date

2013-02-03T19:17:37Z

Director of Research (if dissertation) or Advisor (if thesis)

Insana, Michael F.

Doctoral Committee Chair(s)

Insana, Michael F.

Committee Member(s)

• O'Brien, William D.
• Nardulli, Ann M.
• Wang, Peter
• Garada, Masab

Department of Study

Bioengineering

Discipline

Bioengineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• stroma
• fibroblast
• cancer cells
• fractionation and radiation therapy

Abstract

Radiotherapy is central to the management of a number of human cancers, either as an adjuvant or primary treatment modality. The principal objective in irradiating tumors is to permanently inhibit their proliferative ability. More than half of all malignancies are primarily treated with radiation, but the heterotypic nature of tumor cells greatly complicates their response to radiotherapy. The need for reliable parameters to predict tumor and normal tissue response to radiation is therefore a prime concern of clinical oncology. Post-operative radiotherapy has commonly been used for early stage breast cancer to treat residual disease. There is continued debate as to what might be the proper dose per fraction as well as the total dose of radiation that needs to be prescribed to prevent disease recurrence. Countries outside the US have adopted increased dose fractionation (i.e., hypofractionation) schemes for early stage breast cancer as a standard of practice; however there is a lack of confidence in these approaches in the United States. The tumor microenvironment plays a significant role in regulating the progression of carcinomas, although the mechanisms are not entirely clear. The primary objective of this work was to characterize, through mechanobiological and radiobiological modeling, a test bed for radiotherapy fractionation techniques assessment. Our goal is to understand how the tumor microenvironment responds to dose fractionation schemes for Breast Conserving Therapy (BCT). Although carcinomas are the major concern for oncology, in this project, the goal is to understand how the stromal microenvironment influences behavior of the cancer cell populations. By classifying 3-D cellular co-cultures as having a reactive or quiescent stroma using the mechanobiology profile (culture stiffness,cellular activation, differentiation, and proliferation) we aim to differentiate the effectiveness of various fractionation schemes. The benefits of understanding heterotypic signaling in post-surgical breast cancer recurrence would be to assist radiation oncologists in designing an improved therapeutic strategy. To relate the parameters of cellular function to therapeutic prescriptions which offer an enhanced clinical outcome would address the lack of knowledge regarding recurrence of disease, tumor control and whether the tumor microenvironment requires more aggressive treatments. In our work to date, we have developed a three-dimensional co-culture model to determine how alternative dose fractionations affect the post-surgical microenvironment. This work suggests that 3-D co-cultures provide the microenvironmental cues needed to reexamine the radiobiological basis underlying radiation therapy. The findings suggest dose escalation to the tumor region may deactivate the reactive stroma, thus minimizing the cancer promoting environment. Large-fraction irradiation may be used to sterilize residual tumor cells and inhibit activation of intracellular transduction pathways that are promoted during the post-surgical wound-healing period. Wound-healing mechanisms are characterized by angiogenesis, fibroplasia, collagen production and granulation tissue formation all of which impact patient prognosis. In fact, tumor dose escalation trials have been proven to reduce local recurrence rates and thus new approaches to partial breast irradiation and tumor bed boosting using external-beam electrons and intensity-modulated radiotherapy (IMRT) techniques are currently under use. These techniques minimize absorbed dose to healthy breast tissues. Treating the residual cancer cells and the reactive stroma that has been stimulated by wound healing requires that we look at the interplay between cell types as well as the mechanical and biochemical factors driving disease. We have discovered that the reason hypofractionation schemes (larger irradiation fractions per day with less total dose) offer therapeutic advantages to some patients could be that it is more effective at treating the reactive stroma. We can kill the cancer cells at the standard rate (180 cGy/fraction), but we have found the larger fractions specifically inhibit wound healing mechanisms by inactivating stromal fibroblasts. The long term goal would be to reduce recurrence rates for early stage breast cancer by treating postsurgical regions most likely to harbor residual tumor cells. Ionizing radiation stress and its effect on ECM mediated cellular functions continues to be an evolving area of research. This study is an initial step in my career plans to study stromal modulation of epithelial tumors. It is also my career goal to integrate basic science experiments and engineering tools into clinical practice.

Graduation Semester

2012-12

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http://hdl.handle.net/2142/42152

Copyright and License Information

Copyright 2012 Muqeem Qayyum. Appropriate permission from Elsevier as published in (Kass et al. 2007) and from Informa Healthcare (Qayyum & Insana, 2012). As well as reprinted with appropriate permission obtained from (Xu 2010)

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