Joseph E. De Larco

The Potential Role of Neutrophils in Promoting the Metastatic Phenotype of Tumors Releasing Interleukin-8

In the last decade, several groups have shown a direct correlation between the inappropriate or ectopic release of interleukin (IL)-8 by tumor cells in vitro and their growth and metastatic potential using in vivo models of tumor growth. IL-8 is a potent neutrophil chemoattractant. Neutrophils, as “early responders” to wounds and infections, release enzymes to remodel the extracellular matrix of the tissues through which they migrate to reach the site of the wound or infection. It is proposed that the host’s cellular response to IL-8 released by tumor cells enhances angiogenesis and contributes to tumor growth and progression. The activities released by the responding neutrophils could serve as enablers of tumor cell migration through the extracellular matrix, helping them enter the vasculature and journey to new, metastatic sites. The reactive oxygen species produced by neutrophilic oxidases to kill invading organisms have the potential to interact with tumor cells to attenuate their apoptotic cascade and increase their mutational rate. It is proposed that the increase in metastatic potential of tumors ectopically releasing IL-8 is, in part, attributable to their ability to attract neutrophils. Discussed here are possible mechanisms by which the neutrophils responding to ectopic IL-8 contribute to the in vivo growth, progression, and metastatic potential of tumor cells. Possible targets are also presented for the development of therapies to attenuate the effects of the ectopic IL-8 release by tumor cells.

A potential role for interleukin-8 in the metastatic phenotype of breast carcinoma cells.

This study shows a strong correlation between the metastatic potentials of breast carcinoma cell lines and their ectopic expression of interleukin-8 (IL-8). Correlations exist for both constitutive and induced levels of IL-8 released. A correlation was also observed between cell morphology, metastatic potential, and IL-8 profile. Metastatic lines are fusiform in appearance, whereas, nonmetastatic lines are epithelioid. The metastatic potential of two breast carcinoma lines was examined using an orthotopic model of spontaneous metastasis. Metastatic cells formed rapidly growing, poorly differentiated primary tumors that metastasized. Nonmetastatic cells formed rapidly growing differentiated primary tumors that did not produce detectable metastases. Comparison of IL-8 expression by the parental cells and cell cultures developed from primary and metastatic tumors, demonstrates that IL-8 released by cultured cells from the primary tumor is higher than that of the parental cells, and IL-8 released by cultured cells derived from the metastatic lung tumors is greater than that released by cultured cells derived from the primary tumor. These data demonstrate a strong correlation between the metastatic phenotype of a cell and its IL-8 expression, suggesting a role for IL-8 in promoting the metastatic potential of breast tumor cells.

A human fibrosarcoma cell line producing multiplication stimulating activity (MSA)-related peptides.

WE suggested previously that transformed cells may produce and release cellular growth factors capable of interacting with a specific class of cellular receptors, making them unavailable as receptors for external ligands1,2. A prediction of this model was that a human fibrosarcoma line, which had been shown not to bind 125I-labelled multiplication stimulating activity (MSA)2, might be secreting molecules functionally related to MSA. We describe here some properties of growth factors produced by this human tumour cell line, derived from a 25-yr-old female with fibrosarcoma of the leg. The cells produce a family of MSA-related compounds with different molecular weights that can be separated on Sephadex G-75. The major activities correspond to proteins of approximate molecular weight (MW) of 11,000 and 7,000. Both of these fractions stimulate cell division, and will compete with 125I-labelled MSA for its receptors on mouse, rat or human cell membranes. Fibrosarcoma cells in culture may constitute an important alternate source to human serum and plasma for the isolation and characterisation of growth stimulating factors.

Atypical methylation of the interleukin-8 gene correlates strongly with the metastatic potential of breast carcinoma cells

Previously, we have shown that a strong correlation exists between the metastatic potential of breast carcinoma cell lines and their ectopic expression of IL-8. The undifferentiated, highly metastatic cell lines with high metastatic potential produce much more IL-8 than their differentiated lower metastatic counterparts. After eliminating the possibility that transcription factor activity was responsible for differences in IL-8 release, we examined the IL-8 gene for possible epigenetic modifications. Here, we report an aberrant methylation pattern that may be responsible for the differences in IL-8 release between the high and low metastatic cell lines. We determined that none of the deoxycytidylate-phosphate-deoxyguanylate (CpG) sites in the reported IL-8 promoter were methylated in either cell type. Much further upstream in the IL-8 gene, two CpG sites were identified that are differentially methylated. These two sites were fully methylated in the high metastatic cell lines, which produce large quantities of IL-8 and remain unmethylated in the low metastatic cell lines where the IL-8 gene is relatively silent. The DNA methylation results presented here differ from the common epigenetic paradigm in which methylation of promoter CpG islands silences gene expression, suggesting that there are additional epigenetic control mechanisms that as yet have not been fully appreciated or explored.

Paradoxical roles for antioxidants in tumor prevention and eradication

Antioxidants have been shown to provide protection against carcinogens, toxic xenobiotics and oxidative stress. This has led to the hypothesis that the addition of antioxidants to cancer chemotherapeutic regimens could increase their efficacy while reducing the side effects often encountered during treatment. The work described in this study set out to test this hypothesis using two different chemotherapeutics, paclitaxel and FUdR, and three different antioxidants, epigallocatechin gallate, phenethyl isothiocyanate and tert-butylhydroquinone. Experiments were carried out on two different breast carcinoma cell lines, MCF-7 and MDA MB435S. Importantly, we did not observe an enhancement of the efficacy of the chemotherapeutic agents in the twelve combinations tested. In fact, for several combinations, simultaneous treatment with an antioxidant attenuated the efficacy of the chemotherapeutic agent. We also determined that the survival advantage provided by antioxidants is consistent with their ability to induce the expression of genes whose regulatory regions contain antioxidant response elements. Together, these findings suggest that the simultaneous use of antioxidants and chemotherapeutic agents has the potential to attenuate the efficacy of chemotherapy by inducing the expression of enzymes that can detoxify cytotoxic agents. In view of these findings, we suggest that the design of chemotherapeutic regimens that combine antioxidants with chemotherapeutic agents should be considered carefully before being initiated.