The cancer journal from Scientific American最新文献

Unlabelled: For transforming normal fibroblasts to malignant cells, oncogenic Ras mutants such as v-Ha-ras require Rho family GTPases (Rho, Rac, and CDC42) that are responsible for controlling actin-cytoskeleton organization. Ras activates Rac through a PI-3 kinase-mediated pathway. Rac causes uncapping of actin filaments (F-actin) at the plus-ends, through phosphatidylinositol 4,5 bisphosphate (PIP2), and eventually induces membrane ruffling. Several distinct F-actin/PIP2-binding proteins, such as gelsolin, which severs and caps the plus-ends of actin filaments, or HS1, which cross-links actin filaments, have been shown to suppress v-Ha-Ras-induced malignant transformation when they are overexpressed. Interestingly, an F-actin cross-linking drug (photosensitizer) called MKT-077 suppresses Ras transformation. Thus, an F-actin capping/severing drug might also have an anticancer potential.

Purpose: This study was conducted to determine first whether Ras-induced malignant phenotype (anchorage-independent growth) is suppressed by overexpression of the gene encoding a large plus-end F-actin capping protein called tensin and second to test the anti-Ras potential of a unique fungal antibiotic (small compound) called chaetoglobosin K (CK) that also caps the plus-ends of actin filaments.

Methods and results: DNA transfection with a retroviral vector carrying the tensin cDNA was used to overexpress tensin in v-Ha-Ras-transformed NIH 3T3 cells. All stable tensin transfectants rarely formed colonies in soft agar, indicating that tensin suppresses the anchorage-independent growth. The anti-Ras action of CK was determined by incubating the Ras-transformants in the presence of CK in soft agar. Two microM CK almost completely inhibited their colony formation, indicating that CK also suppresses the malignant phenotype. However, unlike tensin, CK causes an apoptosis of Ras-transformed NIH 3T3 cells and, less effectively, of normal NIH 3T3 cells, indicating that CK has an F-actin capping-independent side effect(s). CK-induced apoptosis is at least in part caused by CK-induced inhibition of the kinase PKB/AKT. However, a specific ICE/caspase-1 inhibitor called N1445 completely abolished the CK-induced apoptosis by reactivating PKB, but without affecting the CK-induced suppression of Ras transformation.

Conclusions: Like the F-actin cross-linking drug MKT-077, the F-actin capping drug CK may be useful for the treatment of Ras-associated cancers if it is combined with the ICE inhibitor N1445, which abolishes the side effect of CK. Our observations that two distinct F-actin capping molecules (i.e., tensin and CK) suppress Ras-induced malignant phenotype strongly suggest, if not prove, that capping of actin filaments at the plus-ends alone is sufficient to block one of the Ras signaling pathways essential for its oncogenicity. This notion is compatible with the fact that Ras induces

Background: Appropriate adjuvant chemotherapy for resected head and neck cancer patients has yet to be defined. Multiple trials have noted trends toward improved disease-free survival and local control. The Southwest Oncology Group undertook a feasibility trial of postoperative cisplatin and radiotherapy followed by three cycles of cisplatin and 5-fluorouracil.

Methods: Patients with resected stage III or IV head and neck cancer received cisplatin, 100 mg/m2, on days 1, 22, and 43 of radiotherapy. This therapy was followed by three cycles of cisplatin, 100 mg/m2 or last tolerated dose, and 5-fluorouracil, 1000 mg/m2, on days 1 to 4 every 21 days.

Results: Seventy-two patients from 22 institutions were registered; 68 were evaluable. Sixty-eight patients received radiotherapy. Only 25 of 68 patients (36.7%) were able to complete all six cycles of chemotherapy. Forty-three of 68 patients (63%) completed all three cycles with radiotherapy. Toxicities were tolerable. One toxic death occurred.

Conclusions: It is not feasible to deliver six cycles of chemotherapy postoperatively in the sequence described. Compliance issues need further exploration to define effective adjuvant chemotherapy for head and neck patients.

Purpose: This pilot study was conducted to evaluate the efficacy and toxicity of a new intensive drug regimen, combined with involved-nodal-field radiotherapy, in advanced Hodgkin's disease not treated by chemotherapy.

Patients and methods: From September 1990 to March 1993, 73 evaluable patients with newly diagnosed stage IIB, III (A and B), and IV (A and B) Hodgkin's disease or who were relapsing after primary subtotal or total nodal irradiation were treated with eight cycles of etoposide, epirubicin, bleomycin, cyclophosphamide, and prednisolone (VEBEP) followed by radiotherapy (30-36 Gy) to the nodal site or sites of pretreatment disease. The median duration of follow-up was 68 months.

Results: The complete remission rate was 94% (95% CI: 86-98). At 6 years, freedom from progression and overall survival rates were 78% (95% CI: 68-88) and 82% (95% CI: 73-91), respectively. There was one episode of fatal sepsis after bone marrow aplasia that occurred after VEBEP and extended-field irradiation. Hematologic toxicity during chemotherapy was acceptable; without the support of growth factors, grade IV leukopenia and grade IV neutropenia, as determined within cycles, occurred in 38% and 85% of patients, respectively, but was reversible in the vast majority of patients by the day of treatment recycle. No episodes of epidoxorubicin-related cardiomyopathy or symptomatic pulmonary toxicity were documented. Overt and/or subclinical hypothyroidism occurred in 38% of cases. Gonadal damage was evident in the large majority of male patients but reversible in half of them, whereas permanent sterility was observed in females at least 35 years of age. No secondary leukemia has been so far detected.

Discussion: VEBEP followed by involved-nodal-field radiotherapy is an effective treatment for chemotherapy-naive Hodgkin's disease and is associated to acceptable rates of acute and intermediate-term toxicity. This intensive regimen, which does not routinely require the support of hematopoietic growth factors and can be delivered in an outpatient setting, warrants a prospective comparison in a randomized trial versus one of the more effective standard-combination regimens.

Background: Few effective treatments exist for patients with metastatic melanoma. The United States Food and Drug Administration has approved the use of interferon alfa-2b after the resection of locoregional disease, and dacarbazine or interleukin-2 for the treatment of patients with metastatic melanoma beyond the locoregional area, although many additional agents and combinations of agents are currently in use.

Methods: Between January 1997 and June 1998, the Surgery Branch of the National Cancer Institute conducted a prospective analysis of 226 consecutive patients with metastatic melanoma referred for protocol evaluation. The previous systemic treatments these patients received both before and after the development of metastatic disease were tabulated, along with the association of these treatments with formal institutional protocols. Only the identity of the agents and not the dose or the schedule of treatments was considered in this analysis. Complete information could be obtained from 189 of the 226 patients.

Results: Of the 189 patients evaluated for this study, 135 (71%) received some form of systemic therapy before referral to the National Cancer Institute. Before the development of metastatic disease, 80 patients were administered 25 different systemic treatments, including 23 different agents. After the development of metastatic disease, 53 patients were administered 57 different systemic and regional treatments, including 37 different agents. After the resection of all metastatic sites, 23 patients were administered nine different systemic adjuvant treatments. Overall, 78 different systemic treatments were administered to these patients. The majority of treatments in each group were not associated with formal institutional protocols.

Conclusions: This study has demonstrated that a large number of agents and different combinations of agents are currently being administered to patients before and after the development of metastatic melanoma, and frequently not within the context of an approved institutional protocol. These results indicate a need for more formal evaluation of treatments in prospective protocols and greater standardization of the treatment of patients with melanoma.

Purpose: This study was conducted to obtain and compare the preferences assigned to cancer states and prevention measures by women who had breast cancer, were at high risk for breast cancer, or had neither condition.

Patients and methods: We administered a time trade-off questionnaire to 21 breast cancer patients, 28 women with a personal history of multiple breast biopsies or a family history of breast cancer, and 135 women without these conditions (the reference group). We stratified the reference group into two groups aged 20 to 32 years and 33 to 50 years, respectively.

Results: All four groups assigned higher preference to breast cancer than to ovarian cancer. Both reference groups preferred using a tamoxifen-like drug to having mastectomy or oophorectomy for cancer prevention; the high-risk and breast cancer groups did not. None of the four groups had a preference between prophylactic mastectomy and breast cancer. All the groups were willing to subtract more years from their life expectancy to protect offspring from genetic risk than to protect themselves. Reference group members in the 33- to 50-year age range had lower mean ratings than the breast cancer group for almost all the health states, and breast cancer patients were less willing than other respondents to trade time for health. Most of these differences were not statistically significant. The high-risk group was similar to the older reference group in time trade-off ratings.

Discussion: The time trade-off-based preferences of healthy women may be used to predict the treatment preferences of women with BRCA1/2 mutations. Obtaining healthy women's ratings of treatment outcomes may help health care policy makers envision the consequences of the difficult choices that high-risk women face.