We have used Raman spectroscopy to assess biomolecular changes of two human head and neck cancer xenografts in response to radiation therapy. We injected radiation-sensitive UM-SCC-22B and –resistant UM-SCC-47 cell lines into the flanks of 80 mice to grow tumor xenografts. Animals were distributed into control and radiation groups where the latter group received a single dose of 2 Gy. In vivo Raman spectroscopy was conducted before, 1, 24, and 48 hours after radiation and data were decomposed using principal component analysis and multi variate curve resolution. We found statistically significant differences in biomolecular changes among radiation-sensitive and –resistant groups.
Tumor hypoxia is a critical indicator of poor clinical outcome in patients with cancers of the breast, cervix, and oral cavity. The ability to noninvasively and reliably monitor tumor oxygenation both prior to and during therapy can aid in identifying poor treatment response earlier than is currently possible and lead to effective changes in treatment regimen. Diffuse reflectance spectroscopy (DRS) has been used in several studies to measure tissue scattering, total hemoglobin content (THb), and vascular oxygenation (sO2) in tissue. In this study, we validate in vivo DRS-based measurements of vascular oxygenation using immunohistochemical staining of tumor hypoxia using pimonidazole, an established hypoxia marker. Using tumor xenografts grown from two different head and neck cell lines—UM-SCC-22B and UM-SCC-47—we demonstrate statistically significant negative correlations between tumor hypoxic fraction (HF) and THb (r = − 0.45; p = 0.04) and sO2 (r = − 0.50; p = 0.02). In addition, we also found a statistically significant positive correlation between HF and mean reduced scattering coefficient (r = 0.60; p = 0.005). Our results demonstrate that DRS-based measures of sO2 can provide reliable indirect measurements of tumor hypoxia that can be of significant utility in preclinical and clinical studies.
Currently, anatomical assessment of tumor volume performed several weeks after completion of treatment is the clinical standard to determine whether a cancer patient has responded to a treatment. However, functional changes within the tumor could potentially provide information regarding treatment resistance or response much earlier than anatomical changes. We have used diffuse reflectance spectroscopy to assess the short and long-term re-oxygenation kinetics of a human head and neck squamous cell carcinoma xenografts in response to radiation therapy. First, we injected UM-SCC-22B cell line into the flank of 50 mice to grow xenografts. Once the tumor volume reached 200 mm3 (designated as Day 1), the mice were distributed into radiation and control groups. Members of radiation group underwent a clinical dose of radiation of 2 Gy/day on Days 1, 4, 7, and 10 for a cumulative dose of 8 Gy. DRS spectra of these tumors were collected for 14 days during and after therapy, and the collected spectra of each tumor were converted to its optical properties using a lookup table-base inverse model. We found statistically significant differences in tumor growth rate between two groups which is in indication of the sensitivity of this cell line to radiation. We further acquired significantly different contents of hemoglobin and scattering magnitude and size in two groups. The scattering has previously been associated with necrosis. We furthermore found significantly different time-dependent changes in vascular oxygenation and tumor hemoglobin concentration in post-radiation days.
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