Acute Hypoxia Enhances Spontaneous Lymph Node Metastasis in an Orthotopic Murine Model of Human Cervical Carcinoma

Abstract

An orthotopic mouse model of cervical carcinoma has been used to investigate the relationship between acute (cyclic) hypoxia and spontaneous lymph node metastasis in vivo. The human cervical carcinoma cell line ME-180 was stably transfected to express the fluorescent protein DsRed2, which allowed the in vivo optical monitoring of tumor growth and metastasis by fluorescent microscopy. The surgically implanted primary tumors metastasize initially to local lymph nodes and later to lung, a pattern consistent with the clinical course of the disease. The effect of acute hypoxia on the growth and spread of these tumors was examined by exposing tumor-bearing mice to treatment consisting of exposure to 12 cycles of 10 min 7% O 2 followed by 10 min air (total 4 h) daily during tumor growth. After 21 days, the tumors were excised, lymph node and lung metastases were quantified, and the hypoxic fraction and relative vascular area of the primary tumors were assessed by immunohistochemical staining for the hypoxic marker drug EF5 [2-(2-nitro-1H-imidazole-1-yl)-N-(2,2,3,3,3-pentafluoropropyl) acetamide] and the vascular marker CD31, respectively. In untreated mice, the primary tumor size was directly correlated with lymph node metastatic burden. The acute hypoxia treatment resulted in a significant decrease in the size of the primary tumors at the time of excision. However, the mice in the acute hypoxia group had an increased number of positive lymph nodes (2-4) as compared with control mice (1-3). Lung metastasis was not affected. The acute hypoxia treatment also decreased the relative vascular area in the primary tumors but did not affect the hypoxic fraction. These results suggest that fluctuating oxygenation in cervical carcinoma tumors may reduce tumor growth rate, but it may also enhance the ability of tumor cells to metastasize to local lymph nodes.

The Unfolded Protein Response: A Novel Component of the Hypoxic Stress Response in Tumors

“…Similarly, in soft tissue sarcomas, investigators have also reported that hypoxic soft tissue sarcomas were more likely to metastasize (12,13). These clinical studies are supported by laboratory studies indicating that hypoxia is a strong stimulus for the metastatic spread of tumors (7,14,15). Collectively, these findings provide strong evidence that hypoxia has a profound effect on tumor growth and clinical outcomes.…”

Significance of Polypyrimidine Tract–Binding Protein 1 Expression in Colorectal Cancer

“…In the strongly positive group, lymphatic invasion, venous invasion, and number of buddings were significantly higher than the negative/weakly positive group (Table 1). Because hypoxia promotes lymph node metastasis (16,17), we performed coimmunostaining for PTBP1 and CAIX in the early-stage clinical specimens. PTBP1-positive cases (Fig.…”

Acidic Extracellular pH Promotes Experimental Metastasis of Human Melanoma Cells in Athymic Nude Mice

“…Experimental studies addressing the mechanisms behind these clinical observations have been initiated in several laboratories and significant evidence that hypoxia (pO 2 <10 mm Hg) may promote metastasis has been provided (13)(14)(15)(16)(17)(18)(19)(20)(21)(22). Thus, tumor cells exposed to hypoxia in vitro show enhanced invasiveness in Matrigel invasion chambers (13,14) and enhanced lung colonization potential after i.v.…”

“…Moreover, murine and xenografted tumors with high hypoxic fractions metastasize more frequently than genetically equivalent control tumors with low hypoxic fractions, whether high hypoxic fractions are occurring naturally (17,18) or are imposed by irradiating the tumor bed (19,20) or by keeping the host mice in a low-oxygen atmosphere (21,22). The enhanced metastatic potential has been shown to be caused by hypoxia-induced up-regulation of several metastasis-promoting gene products, including proteolytic enzymes, proangiogenic factors, and antiapoptotic proteins (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23).…”