Drosophila CRC Models to Study Tumor-Promoting Signaling Interactions

Date of Award

5-1-2025

Degree Name

M.S. in Biology

Department

Department of Biology

Advisor/Chair

Madhuri Kango-Singh

Abstract

Among the general hallmarks of cancer are dysregulated proliferative signaling and tumor heterogeneity, with diverse genetic alterations inducing the activity of various interconnected signaling pathways and ultimately posing a significant challenge to targeted pharmacological treatment. Colorectal cancer (CRC) stands as the third-most diagnosed malignancy, and invasive surgical intervention remains the predominant method of treatment. CRC is characterized by high co-occurrence of mutations in the tumor suppressor gene APC, the proto-oncogene KRAS, and the dual tumor suppressor and proto-oncogene TP53. These genetic lesions implicate the Wnt, Ras-MAPK, and DNA damage repair pathways in the initiation and progression of neoplastic growth in the intestinal epithelium, raising questions regarding how these pathways and others such as JNK and Hippo interact in the aberrant control of cellular proliferation, cell cycle progression, growth, and cell death. Using the Drosophila intestine as a model, this study sought to investigate the signaling interactions underlying initiation and progression of CRC in the context of dominant-negative p53, oncogenic RasG12V, and loss-of-function APC. The mosaic analysis with a repressible cell marker (MARCM) technique was used alongside escargot-GAL4 to drive the expression of these mutant transgenes specifically in intestinal stem cells in early larvae and adults. Through the generation of one-hit, two-hit, and three-hit models of CRC expressing p53DN, RasV12, and APC-/-, we tested for alterations in signaling activity that ultimately drive abnormal proliferation and cell cycle progression in CRC. Molecular phenotypes, including gene expression changes and alterations in growth-regulating pathways, were assessed via dissection of third instar larvae and mature adult flies and immunohistochemistry. Our results support that the expression of dominant-negative p53, oncogenic RasV12, and loss-of-function APC in the larval intestine is sufficient to induce hyperproliferation and alterations in intestinal stem cell (ISC) differentiation without any concurrent increase in cell death, underscored by hyperactivation of Wnt, JNK, and the oncoprotein Yki. Three-hit tumors showcased more marked alterations than those observed in two- or one-hit models, including dramatically increased proliferation, volume, and invasive behavior. Given the close genetic homology between flies and humans, the results of this study are expected to yield meaningful insights into the molecular mechanisms underlying human CRC and to identify signaling components that can be pharmaceutically targeted.

Keywords

Biology, Biomedical Research, Cellular Biology, Genetics, Molecular Biology, Oncology

Rights Statement

Copyright 2025, author.

Link to Full Text

Share

COinS