P‐Glycoprotein Mediated Drug Interactions in Animals and Humans with Cancer

Drug–drug interactions can cause unanticipated patient morbidity and mortality. The consequences of drug–drug interactions can be especially severe when anticancer drugs are involved because of their narrow therapeutic index. Veterinary clinicians have traditionally been taught that drug–drug interactions result from alterations in drug metabolism, renal excretion or protein binding. More recently, drug–drug interactions resulting from inhibition of P‐glycoprotein‐mediated drug transport have been identified in both human and veterinary patients. Many drugs commonly used in veterinary patients are capable of inhibiting P‐glycoprotein function and thereby causing an interaction that results in severe chemotherapeutic drug toxicity. The intent of this review is to describe the mechanism and clinical implications of drug–drug interactions involving P‐glycoprotein and anticancer drugs. Equipped with this information, veterinarians can prevent serious drug–drug interactions by selecting alternate drugs or adjusting the dose of interacting drugs.     

The immunophenotype of peripheral blood lymphocytes in clinically healthy dogs and dogs with lymphoma in remission

Lymphoma is a common cancer of dogs that frequently is treated with chemotherapy or radiation therapy. Response to therapy is variable and currently available diagnostic tests do not reliably predict response to therapy. Treatment for lymphoma often results in lymphopenia, but it is unknown whether the changes in circulating lymphocytes result from generalized or specific reduction of lymphocytes. In this study, blood lymphocytes from 12 clinically healthy dogs, 10 dogs in remission because of treatment for B-cell lymphoma, and 8 dogs in remission from T-cell lymphoma were analyzed by flow cytometry by using a panel of 20 antibodies reactive with canine leukocyte antigens. Results identified similar lymphocyte parameters in treated dogs regardless of the type of lymphoma. Treated dogs had >50% reduction in blood lymphocyte concentration, and an absolute decrease in most subsets of lymphocytes. Both groups of treated dogs had relative increases in the proportion of CD3+, T-cell receptor (TCR)αβ+, and CD90+ lymphocytes, and a decreased proportion of CD45RA+ cells. In addition, dogs with T-cell lymphoma in remission had a significant increase in the proportion of CD49d+ lymphocytes. These findings were interpreted as representing likely suppression of lymphocyte regeneration by chemotherapy, with a relative increase in the proportion of memory over naïve lymphocytes. Lack of correlation with the T- or B-cell origin of the initial lymphoma suggested that, by using flow cytometric methods, residual circulating neoplastic cells could not be detected. However, the changes in the lymphocyte profile of dogs treated with chemotherapy may have relevance to their immunocompetence.     

Cultivation and identification of human colon cancer stem cell-like cells and antiproliferative effects of n-3 polyunsaturated fatty acids

AIM: To cultivate stem-like spheres from SW620 cell line in the specific serum-free medium and evaluate the features of the cancer stem cells, and to investigate the effects of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) on the growth of SW620 stem cell-like cells. METHODS: Human colon cancer stem cell-like cells (CSCLC) were obtained from SW620 spheres cultured in serum-free medium. These cells were tested for the expression of SSEA-1 and TRA-1-81 by immunofluorescence staining. The mRNA expression of Sox-2 and Oct-4 was detected by real-time PCR. The efficiency of colony formation on a soft agar gel and tumor formation in the nude mice was compared between SW620 adherent cells and CSCLC. The inhibitory effects of 5-fluorouracil (5-FU) and mitomycin C on both types of cells were measured by MTS assay. MTS assay, Annexin V/PI staining and trypan blue staining were used to determine the effects of DHA and EPA on both types of cells. MTS assay was also used to analyze the combined effect of DHA or EPA with chemotherapeutic drugs on SW620 CSCLC. RESULTS: SW620 cells formed spheres in serum-free culture. The cells from spheres highly expressed SSEA-1 and TRA-1-81, transiently expressed Sox-2 and Oct-4genes and were more resistant to 5-FU and mitomycin C treatments. These cells exhibited a greater ability in clone formation and tumorigenicity, indicating that these cells carried stem cell-like features, hence were considered SW620-derived CSCLC. DHA and/or EPA suppressed SW620 CSCLC by inhibiting cell growth, inducing cell apoptosis and sensitizing them to chemotherapeutic drugs. CONCLUSION: The cells with stem cell-like features, such as high efficiency in clonogenicity, tumorigenicity and resistance to chemotherapeutic drugs, can be obtained from SW620 spheres cultured in serum-free condition. DHA and EPA induce apoptosis in SW620-derived CSCLC and sensitize them to chemotherapeutic drugs.     

Survival Analysis of 97 Cats with Nasal Lymphoma: A Multi-Institutional Retrospective Study (1986–2006)

Background: Feline nasal lymphoma (NLSA) is a condition for which no standard of care exists.
Hypothesis: There is no difference in survival times of cats with NLSA treated with single or multimodality therapy.
Animals: Records from 97 cats diagnosed with NLSA were examined.
Methods: The purpose of this retrospective study was to compare the survival times of cats with NLSA treated with radiation therapy (RT) alone, chemotherapy alone, or RT + chemotherapy and identify potential prognostic variables that affected survival. Cats were grouped according to therapy: RT + chemotherapy (n = 60), RT alone (n = 19), or chemotherapy alone (n = 18).
Results: Survival was calculated with 2 methods. The 1st survival analysis (method A) included all cats, but counted only deaths caused by progressive NLSA. The median survival time (MST), regardless of therapy modality, was 536 days. The 2nd survival analysis (method B) also included all cats and counted all deaths, regardless of cause, as events. The overall MST calculated for all deaths was 172 days. A negative independent prognostic variable identified was anemia ( P < .001), and positive independent prognostic variables were a complete response to therapy ( P < .001) and total radiation dose >32 Gy ( P = .03).
Conclusions and Clinical Importance: There were no significant differences in survival times among the 3 treatment groups but these results suggest that the addition of higher doses of RT to a cat's treatment protocol may control local disease and therefore influence survival.     

Postoperative adjuvant treatment of invasive malignant mammary gland tumors in dogs with doxorubicin and docetaxel

BACKGROUND: Treatment outcome after surgery alone is unsatisfactory in dogs with invasive malignant mammary gland tumors. HYPOTHESIS: Adjuvant doxorubicin or docetaxel will improve the treatment outcome in dogs with high-risk malignant mammary gland tumors, and the use of docetaxel will be feasible in affected dogs. ANIMALS: Thirty-one dogs with malignant mammary gland tumors of histologic stages II and III (vascular or lymphatic invasion, regional lymph node metastasis, or distant metastasis) were used. METHODS: A prospective clinical trial in which dogs were treated with surgery alone (n = 19) or also received adjuvant chemotherapy (n = 12) with doxorubicin or docetaxel was conducted. Docetaxel was given as an IV infusion at a dose of 30 mg/m2 preceded by dexamethasone and diphenhydramine administration. RESULTS: The recurrence-free interval ranged from 13 to 2,585 days (median not reached); the median metastasis-free interval and overall survival were 294 days and 370 days, respectively. Dogs treated with chemotherapy had a tendency toward higher long-term local control and survival rates, but there was no significant difference in the recurrence-free interval (P = .17), time to metastasis (P = .71), and overall survival (P = .12). Factors found to influence the time to metastasis and overall survival included lymph node metastasis (P = .009) and tumor fixation to underlying structures (P = .043, time to metastasis), as well as age (P = .018) and histologic stage (P < .001, survival). Mild allergic skin reactions were the most frequently observed complications of docetaxel treatment. CONCLUSIONS AND CLINICAL IMPORTANCE: Chemotherapy did not lead to an improved outcome in this population. Docetaxel treatment was well tolerated. Additional investigations of adjuvant chemotherapy in dogs with high-risk mammary cancer are warranted.     

肿瘤细胞三种药敏测试方法的比较研究

以人早幼粒白血病细胞系ＨＬ－６０为对象，进行了ＭＴＴ法细胞浓度曲线和五种抗癌药物的敏感试验，并与台盼蓝拒染法、￣３Ｈ－ＴｄＲ掺入法进行了比较，结果表明在一定活细胞范围内（１．２５×１０￣４～２×１０￣５），ＭＴＴ法所测光密度与细胞数成线性关系（ｒ＝０．９９８０，Ｐ＜０．０５）；三种方法测定的５－Ｆｕ、ＭＴＸ、ＶＣＲ、Ｈ、Ａｒａ－Ｃ药物敏感性结果一致，ＭＴＴ法灵敏度与台盼蓝拒染法相似（Ｐ＞０．０５），但低于￣３Ｈ－ＴｄＲ掺入法（Ｐ＜０．０５）。     

Low-dose cyclophosphamide selectively decreases regulatory T cells and inhibits angiogenesis in dogs with soft tissue sarcoma

Background: Low‐dose, continuous (metronomic) chemotherapy improves tumor control by inhibiting tumor angiogenesis and suppressing regulatory T cells (Treg) in mice and humans. The effects of metronomic chemotherapy on Treg and tumor angiogenesis in dogs has not been investigated previously. Objective: To determine whether metronomic cyclophosphamide (CYC) therapy decreases Treg or exhibits antiangiogenic activity or both in dogs with soft tissue sarcoma (STS). We hypothesized that Treg numbers would be increased in dogs with STS and that continuous dosing of CYC would decrease Treg in a dose‐dependent manner, as well as exhibit antiangiogenic activity. Animals: Eleven client‐owned dogs with grade I or II STS. Twenty‐one healthy dogs were used as controls. Methods: Prospective, open, clinical trial. Dogs with STS were enrolled in 2 dose cohorts and administered CYC at 12.5 or 15 mg/m² PO once daily for 28 days. Whole blood and tumor biopsy specimens were obtained on days 0, 14, and 28 to assess changes in T lymphocyte subsets by flow cytometry and tumor microvessel density (MVD), respectively. Results: Administration of CYC at 12.5 mg/m²/d significantly decreased the number of Treg from days 0 to 28, but there was no change in the percentage of Treg or tumor MVD. In dogs that received CYC at 15.0 mg/m²/d, both the number and percent of Treg as well as tumor MVD were significantly decreased over 28 days. Conclusions: CYC administered at 15 mg/m²/d should be used in further studies examining the antitumor properties of low‐dose CYC in dogs.