Exploiting Cancer's Tactics to Make Cancer a Manageable Chronic Disease.

The history of modern oncology started around eighty years ago with the introduction of cytotoxic agents such as nitrogen mustard into the clinic, followed by multi-agent chemotherapy protocols. Early success in radiation therapy in Hodgkin lymphoma gave birth to the introduction of radiation therapy into different cancer treatment protocols. Along with better understanding of cancer biology, we developed drugs targeting cancer-related cellular and genetic aberrancies. Discovery of the crucial role of vasculature in maintenance, survival, and growth of a tumor opened the way to the development of anti-angiogenic agents. A better understanding of T-cell regulatory pathways advanced immunotherapy. Awareness of stem-like cancer cells and their role in cancer metastasis and local recurrence led to the development of drugs targeting them. At the same time, sequential and rapidly accelerating advances in imaging and surgical technology have markedly increased our ability to safely remove ≥90% of tumor cells. While we have advanced our ability to kill cells from multiple directions, we have still failed to stop most types of cancer from recurring. Here we analyze the tactics employed in cancer evolution; namely, chromosomal instability (CIN), intra-tumoral heterogeneity (ITH), and cancer-specific metabolism. These tactics govern the resistance to current cancer therapeutics. It is time to focus on maximally delaying the time to recurrence, with drugs that target these fundamental tactics of cancer evolution. Understanding the control of CIN and the optimal state of ITH as the most important tactics in cancer evolution could facilitate the development of improved cancer therapeutic strategies designed to transform cancer into a manageable chronic disease.

Dual antivascular function of human fibulin-3 variant, a potential new drug discovery strategy for glioblastoma.

The ECM protein EFEMP1 (fibulin-3) is associated with all types of solid tumor through its cell context-dependent dual function. A variant of fibulin-3 was engineered by truncation and mutation to alleviate its oncogenic function, specifically the proinvasive role in glioblastoma multiforme (GBM) cells at stem-like state. ZR30 is an in vitro synthesized 39-kDa protein of human fibulin-3 variant. It has a therapeutic effect in intracranial xenograft models of human GBM, through suppression of epidermal growth factor receptor/AKT and NOTCH1/AKT signaling in GBM cells and extracellular MMP2 activation. Glioblastoma multiforme is highly vascular, with leaky blood vessels formed by tumor cells expressing endothelial cell markers, including CD31. Here we studied GBM intracranial xenografts, 2 weeks after intratumoral injection of ZR30 or PBS, by CD31 immunohistochemistry. We found a 70% reduction of blood vessel density in ZR30-treated xenografts compared with that of PBS-treated ones. Matrigel plug assays showed the effect of ZR30 on suppressing angiogenesis. We further studied the effect of ZR30 on genes involved in endothelial transdifferentiation (ETD), in 7 primary cultures derived from 3 GBMs under different culture conditions. Two GBM cultures formed mesh structures with upregulation of ETD genes shortly after culture in Matrigel Matrix, and ZR30 suppressed both. ZR30 also downregulated ETD genes in two GBM cultures with high expression of these genes. In conclusion, multifaceted tumor suppression effects of human fibulin-3 variant include both suppression of angiogenesis and vasculogenic mimicry in GBM.

Human fibulin-3 protein variant expresses anti-cancer effects in the malignant glioma extracellular compartment in intracranial xenograft models.

BACKGROUND: Decades of cytotoxic and more recently immunotherapy treatments for malignant glioma have had limited success due to dynamic intra-tumoral heterogeneity. The dynamic interplay of cancer cell subpopulations has been found to be under the control of proteins in the cancer microenvironment. EGF-containing fibulin-like extracellular matrix protein (EFEMP1) (also fibulin-3) has the multiple functions of suppressing cancer growth and angiogenesis, while promoting cancer cell invasion. EFEMP1-derived tumor suppressor protein (ETSP) retains EFEMP1's anti-growth and anti-angiogenic functions while actually inhibiting cancer cell invasion. METHODS: In this study, we examined the therapeutic effect on glioblastoma multiforme (GBM) of an in vitro synthesized protein, ZR30, which is based on the sequence of ETSP, excluding the signaling peptide. RESULTS: ZR30 showed the same effects as ETSP in blocking EGFR/NOTCH/AKT signaling pathways, when applied to cultures of multiple GBM cell lines and primary cultures. ZR30's inhibition of MMP2 activation was shown not only for GBM cells, but also for other types of cancer cells having overexpression of MMP2. A significant improvement in survival of mice with orthotopic human GBM xenografts was observed after a single, intra-tumoral injection of ZR30. Using a model mimicking the intra-tumoral heterogeneity of GBM with cell subpopulations carrying different invasive and proliferative phenotypes, we demonstrated an equal and simultaneous tumor suppressive effect of ZR30 on both tumor cell subpopulations, with suppression of FOXM1 and activation of SEMA3B expressions in the xenografts. CONCLUSION: Overall, the data support a complementary pleiotrophic therapeutic effect of ZR30 acting in the extracellular compartment of GBM.

Chronic inflammation: is it the driver or is it paving the road for malignant transformation?

Chronic inflammation in well-defined mouse models such as Giα2 knock out mouse has been shown to trigger formation and expansion of hypoxic niches and also leads to up regulation of NFĸB, offering cells which have adapted their genetic machinery to hypoxia a unique survival advantage. These adapted cells have been shown to acquire stem cell-like capabilities as shown by up regulation of stem cell markers. Such long lived cells become permanent residents in sub mucosa and acquire a malignant phenotype from long-term exposure to noxious environmental agents due to a barrier defect secondary to down regulation of barrier proteins such as Zo1 and Occludin. Indeed mitotic spindle disorientation in such mice has been proposed as another contributory factor to malignant transformation. Sterilization of bowel lumen of these mice through different techniques has prevented malignant transformation in the presence of chronic inflammation. These facts stand strongly against chronic inflammation as a true driver of carcinogenesis but clearly support its role in facilitating the emergence of the neoplastic clone.

Disruption of Paneth and goblet cell homeostasis and increased endoplasmic reticulum stress in Agr2-/- mice.

Anterior Gradient 2 (AGR2) is a protein disulfide isomerase that plays important roles in diverse processes in multiple cell lineages as a developmental regulator, survival factor and susceptibility gene for inflammatory bowel disease. Here, we show using germline and inducible Agr2-/- mice that Agr2 plays important roles in intestinal homeostasis. Agr2-/- intestine has decreased goblet cell Mucin 2, dramatic expansion of the Paneth cell compartment, abnormal Paneth cell localization, elevated endoplasmic reticulum (ER) stress, severe terminal ileitis and colitis. Cell culture experiments show that Agr2 expression is induced by ER stress, and that siRNA knockdown of Agr2 increases ER stress response. These studies implicate Agr2 in intestinal homeostasis and ER stress and suggest a role in the etiology of inflammatory bowel disease.

Epigenetic repression of DNA mismatch repair by inflammation and hypoxia in inflammatory bowel disease-associated colorectal cancer.

Sporadic human mismatch repair (MMR)-deficient colorectal cancers account for approximately 12.5% of all cases of colorectal cancer. MMR-deficient colorectal cancers are classically characterized by right-sided location, multifocality, mucinous histology, and lymphocytic infiltration. However, tumors in germ-line MMR-deficient mouse models lack these histopathologic features. Mice lacking the heterotrimeric G protein alpha subunit Gialpha2 develop chronic colitis and multifocal, right-sided cancers with mucinous histopathology, similar to human MMR-deficient colorectal cancer. Young Gialpha2-/- colonic epithelium has normal MMR expression but selectively loses MLH1 and consequently PMS2 expression following inflammation. Gialpha2-/- cancers have microsatellite instability. Mlh1 is epigenetically silenced not by promoter hypermethylation but by decreased histone acetylation. Chronically inflamed Gialpha2-/- colonic mucosa contains patchy hypoxia, with increased crypt expression of the hypoxia markers DEC-1 and BNIP3. Chromatin immunoprecipitation identified increased binding of the transcriptional repressor DEC-1 to the proximal Mlh1 promoter in hypoxic YAMC cells and colitic Gialpha2-/- crypts. Treating Gialpha2-/- mice with the histone deacetylase inhibitor suberoylanilide hydroxamic acid significantly decreased colitis activity and rescued MLH1 expression in crypt epithelial cells, which was associated with increased acetyl histone H3 levels and decreased DEC-1 binding at the proximal Mlh1 promoter, consistent with a histone deacetylase-dependent mechanism. These data link chronic hypoxic inflammation, epigenetic MMR protein down-regulation, development of MMR-deficient colorectal cancer, and the firstmouse model of somatically acquired MMR-deficient colorectal cancer.

Familial colorectal cancer syndrome X.

In recent decades there have been significant advances in our understanding of the genes that underlie hereditary susceptibility to colorectal cancer (CRC). In 2007 it is well established that mutations in DNA repair genes (MLH1, MSH2, MSH6, MYH) and Wnt pathway signal transduction inhibitors (APC) underlie a significant percentage of hereditary CRC susceptibility. However, it also is clear that the known CRC susceptibility genes do not explain fully the inherited risk seen even in families meeting the revised Bethesda guidelines. Furthermore, the optimal medical management of these syndromes is still being defined. What underlies CRC susceptibility in these highly unusual families that do not have identifiable mutations in the known genes, often referred to as syndrome X? This review addresses this important question that is relevant to our current understanding of the management of individuals with hereditary predisposition to CRC.