Safety evaluation of immune-cell therapy for malignant tumor in the Cancer Immune-cell Therapy Evaluation Group (CITEG).

BACKGROUND AIMS: With the aim of strengthening the scientific evidence of immune-cell therapy for cancer and further examining its safety, in October 2015, our hospital jointly established the Cancer Immune-Cell Therapy Evaluation Group (CITEG) with 39 medical facilities nationwide. METHODS: Medical information, such as patients' background characteristics, clinical efficacy and therapeutic cell types obtained from each facility, has been accumulated, analyzed and evaluated by CITEG. In this prospective study, we analyzed the adverse events associated with immune-cell therapy until the end of September 2022, and we presented our interim safety evaluation. RESULTS: A total of 3839 patients with malignant tumor were treated with immune-cell therapy, with a median age of 64 years (range, 13-97 years) and a male-to-female ratio of 1:1.08 (1846:1993). Most patients' performance status was 0 or 1 (86.8%) at the first visit, and 3234 cases (84.2%) were advanced or recurrent cases, which accounted for the majority. The total number of administrations reported in CITEG was 31890, of which 960 (3.0%) showed adverse events. The numbers of adverse events caused by treatment were 363 (1.8%) of 19661 administrations of αßT cell therapy, 9 of 845 administrations of γδT-cell therapy (1.1%) and 10 of 626 administrations of natural killer cell therapy (1.6%). The number of adverse events caused by dendritic cell (DC) vaccine therapy was 578 of 10748 administrations (5.4%), which was significantly larger than those for other treatments. Multivariate analysis revealed that αßT cell therapy had a significantly greater risk of adverse events at performance status 1 or higher, and patients younger than 64 years, women or adjuvant immune-cell therapy had a greater risk of adverse events in DC vaccine therapy. Injection-site reactions were the most frequently reported adverse events, with 449 events, the majority of which were associated with DC vaccine therapy. Among all other adverse events, fever (228 events), fatigue (141 events) and itching (131 events) were frequently reported. In contrast, three patients had adverse events (fever, abdominal pain and interstitial pneumonia) that required hospitalization, although they were weakly related to this therapy; rather, it was considered to be the effect of treatment for the primary disease. CONCLUSIONS: Immune-cell therapy for cancer was considered to be a safe treatment without serious adverse events.

Development of adoptive immunotherapy with KK-LC-1-specific TCR-transduced γδT cells against lung cancer cells.

The present study analyzed the antitumor effect of γδT cells transduced with the TCR of cancer-specific CTLs to establish forceful cancer-specific adoptive immunotherapy. We cloned the TCRαß genes from CTLs showing HLA-B15 restricted recognition of Kita-Kyushu lung cancer antigen-1 (KK-LC-1), a cancer/germline gene antigen, identified in a lung adenocarcinoma case (F1121). The TCRαß and CD8 genes were transduced into γδT cells induced from PBLs of healthy volunteers stimulated with zoledronate and IL-2. The KK-LC-1-specific TCRαß-CD8 γδT cells showed cytotoxic activity against the KK-LC-1 positive lung cancer cell line F1121L and produced IFN-γ against F1121L and KK-LC-1 peptide-pulsed F1121 EBV-B cells. These responses were blocked by HLA class I and HLA-B/C antibodies. An in vivo assay using NOD/SCID mice with xenotransplantation of human lung cancer cells was performed, and the TCRαß-CD8 transduced γδT cells (TCRαß-CD8 γδT cells) were intravenously injected. Growth inhibition of KK-LC-1+ , HLA-B15+ lung cancer cells was confirmed in mice with injection of the TCRαß-CD8 γδT cells from 1 wk after xenotransplantation of cancer cells but not in those treated 2 wk after xenotransplantation. The resected specimens of the tumor, 2 wk after xenotransplantation, highly expressed FasL but not programmed death ligand-1 (PD-L1) by immunohistochemical staining. FasL highly expressed cancer cells xenotransplanted 2 wk ago were resistant to TCRαß-CD8 γδT cells injection. These results suggested that apoptosis of Fas-positive TCRαß-CD8 γδT cells may be induced by a Fas-mediated signal after interacting with FasL-positive cancer cells.

Identification of prognostic factors for γδT cell immunotherapy in patients with solid tumor.

BACKGROUND AIMS: Activated γδT cells have been shown to exhibit cytotoxicity against tumor cells. However, the efficacy of γδT cell immunotherapy for a large number of patients with solid tumors remains unclear. In this study, we examined the efficacy of γδT cell immunotherapy using in vitro-activated γδT lymphocytes in combination with standard therapies in terms of the survival of patients with solid tumors, and determined prognostic factor for γδT cell immunotherapy. METHODS: 131 patients enrolled in this study received γδT cell immunotherapy with or without standard therapies. Their overall survival was analyzed by the Kaplan-Meier with log-rank test and Cox regression methods. Immunological analysis was performed by flow cytometry (FCM) before and after six cycles of γδT cell immunotherapy. RESULTS: Multivariable analysis revealed that patients who showed stable disease (SD) and partial response (PR) to γδT cell immunotherapy showed better prognosis than those with a progressive disease (PD) (P = 0.0269, hazard ratio [HR], 0.410, 95% confidence interval [CI], 0.190-0.901). Furthermore, when immunological parameters were examined by FCM, the high Vγ9/γδT ratio (i.e., the high purity of the Vγ9 cells within the adoptively transferred γδT cells) before treatment was found to be a good prognostic factor for γδT cell immunotherapy (P = 0.0142, HR, 0.328, 95% CI, 0.125-0.801). No serious adverse events were reported during γδT cell immunotherapy. CONCLUSION: Thus, γδT cell immunotherapy might extend the survival of patients with solid tumors.

[Clinical significance of micrometastases in the lymph nodes of patients with resectable lung cancer].

Clinical evaluation of micrometastases in the lymph nodes of lung cancer patients is not currently recommended in guidelines because of several different results concerning their prevalence and prognostic implications. However, a recent large, prospective, multicenter clinical study has shown a significant prognostic impact of micrometasteses in the lymph nodes of patients with resectable lung cancer; therefore, the clinical significance of micrometastases as predictive markers of recurrence and prognosis has begun to be clarified. From the viewpoint of surgery for lung cancer, sentinel node navigation surgery, segmentectomy, and individualized therapies such as adjuvant chemotherapy are expected to be developed. In the near future, standardization and improvement of the efficiency of diagnostic procedures will be necessary in common clinical practice. Recently, minimal residual cancer cell research, such as circulating tumor cells in the peripheral blood and disseminated tumor cells in the bone marrow, has made good progress. As research in this field continues, it is expected that the mechanism of metastasis and novel therapeutic strategies targeting minimal residual cancer cells will become better understood.

Differences in sensitivity to tumor-specific CTLs between primary and metastatic esophageal cancer cell lines derived from the same patient.

PURPOSE: MHC antigens and adhesion molecules, such as the intracellular adhesion molecule (ICAM-I), play an important role in cellular immune response. We examined the expression patterns of these molecules in both primary and metastatic esophageal carcinoma cells from the same patient and evaluated the cellular immune responses against these cells. MATERIALS AND METHODS: In the esophageal cancer patient (H122), tumor cell lines were established from primary and subcutaneous metastatic lesions. We compared the expression of cell surface molecules on the metastatic tumor cell line (H122SC) with that on the primary tumor cell line (H122ESO) using flow cytometry. Moreover, we analyzed the differences in cellular immune responses against these cell lines, which expressed similar levels of the Tara antigen, using the Tara antigen-specific CTL clone. RESULTS: H122SC ICAM-1 expression was significantly lower in H122ESO, and the Tara antigen-specific CTL clone produced lower levels of TNF in response to H122SC than H122ESO. ICAM-1 transfection into the H122SC rendered these cells as sensitive to the CTL clone as the H122ESO. CONCLUSION: The metastatic tumor cells displayed lower regulated ICAM-1 expression levels and were less sensitive to specific CTLs. ICAM-1 downregulation may be one mechanism by which tumor cells escape immunologic surveillance.

Pleural lavage cytology immediately after thoracotomy in patients with completely resected non-small cell lung cancer.

This study evaluated 325 patients who had undergone pleural lavage cytology (PLC) immediately after thoracotomy following a complete resection for non-small cell lung cancer (NSCLC) between 2004 and 2008. The number of patients with negative and positive findings in PLC was 309 and 13, respectively. The proportion of T1 in the PLC-positive group was significantly smaller than that of the PLC-negative group. The pathologic examinations revealed that the parietal pleural invasion was significantly more severe in the PLC-positive group than in the PLC-negative group. Pathologic lymphovascular invasion was also significantly more prominent in the PLC-positive group than in the PLC-negative group. The 5-year survival rate after surgery in the PLC-positive group and PLC-negative group was 54.7% and 79.0%, respectively. The positive finding in PLC showed a tendency of an unfavorable prognosis for NSCLC patents following complete resection. Further clinical studies will be necessary to evaluate the efficacy of adjuvant therapy for PLC-positive patients.

[Clinical analysis of esophageal cancer associated with other primary cancers].

This study aims to investigate the therapeutic and prognostic implications of esophageal cancer in patients with other primary cancer. Between April 1992 and December 2008, in 83 patients underwent surgery for esophageal cancer at our department. Among them, 24 patients (28.9%) had medical history of additional primary cancer. There were 16 metachronous cancers and 8 synchronous cancers. Six patients had antecedent other primary cancers, and subsequent primary cancers developed in 10 patients. The other primary cancers included head and neck cancer in 8 patients, gastric cancer in 8, lung cancer in 6, colorectal cancer in 3, and other cancer in 3. The patients with other primary cancers were both heavy smokers and heavy drinkers in comparison to those without other primary cancers. The post-operative 5-year survival rate in patients with subsequent cancers, antecedent cancers, and synchronous cancers were 100%, 70.0%, and 46.9%. The 5-year survival rate was 33.4% in patients without other primary cancers. A high incidence of multiple primary cancers was observed in patients with esophageal carcinoma but the prognosis of these patients with metachronous cancers are better than that of patient with synchronous cancers and patients without other primary cancers. Post-operative follow up is considered to be necessary for early detection of multiple occurrences of carcinoma, especially in the upper aerodigestive tract.

Identification of ribosomal protein L19 as a novel tumor antigen recognized by autologous cytotoxic T lymphocytes in lung adenocarcinoma.

The purpose of the present study was to identify a novel tumor-specific antigen capable of inducing a specific cellular immune response in lung cancer patients. The co-culture of regional lymph node lymphocytes and the CD80-transfected autologous lung adenocarcinoma cell line H1224L resulted in a successful induction of bulk cytotoxic T lymphocytes (CTL). CTL clone L7/8 was established by the limiting dilution method from these bulk CTLs and lysed H1224L but not autologous Epstein-Barr virus-transformed B cells or K562. The CTL clone also recognized allogeneic lung cancer cell lines in an HLA-A*31012-restricted manner. Using the CTL clone, an antigen-coding gene was identified using the cDNA expression cloning technique, which encodes ribosomal protein L19 (RPL19). Finally, a 9 mer antigenic peptide was identified by means of construction of mini-genes. RPL19 was overexpressed in the lung cancer tissue from patient H1224. All of the normal tissues examined expressed lower levels of RPL19 mRNA than that of the lung cancer tissue. RPL19 was also found to be overexpressed in 12 of 30 (40%) non-small-cell lung cancer tissues by immunohistochemical staining. The expression level of RPL19 in tumor cell lines correlated positively with the production of interferon (IFN)-gammaby CTL clone L7/8 in response to such cell lines. In addition, the suppression of RPL19 expression by transfection with small interfering RNA resulted in the suppression of cyclinD1, D3 synthesis, and the growth inhibition of lung cancer cell lines overexpressing RPL19. Therefore, this growth suppression could be ascribed to the inhibition of the cell cycle. These results may indicate that RPL19 is a novel overexpressed antigen which may therefore be a useful candidate as a target for specific immunotherapy.

Identification of a lung cancer antigen evading CTL attack due to loss of human leukocyte antigen (HLA) class I expression.

The human lung cancer cell line, C831L, lost HLA class I expression due to a mutation of the ß2-microglobulin (ß2m) gene, and it may have been the result of immunoediting by CTL cytotoxicity. By restoration of HLA class I expression, we could identify the antigen that may be associated with HLA downregulation. Such an antigen might be a promising target of immunotherapy because it potentially may induce a sufficient immune response to eradicate cancer cells. The CTL clone could be established from lymph node lymphocytes in patient C831 by stimulation with wild-type ß2m-transduced C831L (C831L-wß2m). The CTL clone showed reactivity against C831L-wß2m in a HLA-B*0702-restricted manner, but not Parental-C831L or autologous normal cells. The cDNA expression cloning method was used to identify the antigen coding gene recognized by the CTL clone. The cDNA clone exhibited a homology with a part of the mRNA that codes for leucine rich repeat containing eight family member A (LRRC8A). A transfection analysis of minigenes indicated that the antigen peptide was derived from protein translated from the downstream of the registered open reading frame in LRRC8A mRNA. The antigenic 9-mer peptide (GPRESRPPA) was identified. The present methodology should be useful to find the crucial tumor antigens, which are potentially associated with loss of HLA expression. Furthermore, such an antigen may help in achieving a better understanding of the immunological escape mechanisms and it may also provide a favorable immune response in cancer immunotherapy.

Mediastinal metastasis from a fibrolamellar hepatocellular carcinoma: Report of a case.

Fibrolamellar hepatocellular carcinoma (FL-HCC) is an uncommon clinicopathological variant of hepatocellular carcinoma (HCC). The etiology of FL-HCC is unknown, but FL-HCC is not associated with hepatic viruses or alcohol. Hepatocellular carcinoma usually occurs in cases of chronic hepatitis or cirrhosis, whereas FL-HCC predominantly occurs in a normal liver and in younger adults. Fibrolamellar HCC shows relatively slow growth, and late recurrence is common. Repeated resections for recurrences should be considered not only because there is a lack of other effective treatment options but also because FL-HCC shows a relatively better prognosis after a resection in comparison to common HCC. This report presents a case of a rare mediastinal metastasis from FL-HCC in a patient who had undergone a previous resection for retroperitoneal metastasis after the initial hepatic operation. This is the second report of the same case. This patient also had a mediastinal neurogenic tumor, and these mediastinal tumors were concurrently resected.

Clinicopathologic characteristics of mucinous carcinoma of the breast.

The mucinous carcinoma of breast cancer is a relatively rare malignant tumor. This study investigated the clinical and pathologic features of mucinous carcinoma. The medical records of 237 patients with invasive breast cancer who underwent surgery between 1995 and 2006 were reviewed. These cases included 10 patients (4.2%) with mucinous carcinoma. The age of the patients ranged from 43 to 71 years (mean, 55.5 years). The tumor size was T1 in 5 patients and T2 in 5 patients. Lymph node metastasis was diagnosed as being negative in 9 patients and positive in 1 patient. Six patients (60%) were positive both for estrogen and progesterone receptor. The 10-year survival rates of mucinous carcinoma and other types of invasive breast cancer were 87.5% and 80.7%, respectively. Mucinous carcinoma showed a lower incidence of lymph node metastasis than other types of invasive breast cancer. Mucinous carcinoma tended to have a better prognosis in comparison with other types of invasive breast carcinoma.

[Results of surgical resection for patients with pulmonary cryptococcosis].

Pulmonary cryptococcosis is a fungal infection caused by inhalation of Cryptococcus neoformans. Pulmonary cryptococcal infections tend to occur in immunocompromised individuals, although they can occasionally develop even in immunocompetent hosts. This report presents a retrospective clinical study of 8 patients who underwent a surgical resection for pulmonary cryptococcosis between 1999 and 2008. The age of the patients ranged from 49 to 85 years old (mean 62.6). There were 4 male and 4 female patients. All patients except for 1 had no symptoms. Two patients were immuno-compromised hosts undergoing corticosteroid therapy due to myasthenia gravis and rheumatoid arthritis, respectively. There were 7 patients with a single nodule and 1 patient with multiple nodules. The tumors ranged from 9 to 21 mm in diameter. None of the patients were definitely diagnosed prior to the surgical resection. The surgical procedures included 5 partial resections, 1 segmentectomy and 2 lobectomies. It is often difficult to make a differential diagnosis between lung cancer and pulmonary cyptococosis, because pulmonary cyptococosis shows similar imaging findings in CT. Therefore, a surgical resection is recommended if an observation of the pulmonary nodes is required to make a differential diagnosis of malignant tumors. All of the patients in the current series showed a good outcome without any relapse including cryptococcal meningitis after a surgical resection.

[Long-term survival after surgical resection of bone metastasis from lung cancer].

BACKGROUND: The prognosis of patients with bone metastasis from primary lung cancer is poor, and the effective treatment for bone metastasis had not been established. We report a case of more than 6 years survival after a surgical resection of rib metastasis. CASE: A 56-years-old woman underwent right lower lobectomy and mediastinal lymph node dissection for lung cancer (well differentiated adenocarcinoma, pT1N0M0, stage IA) in another hospital in July 1995. In May 2003, the patient suffered right lateral chest pain and the chest computed tomography (CT) showed an osteolytic mass of right 5th rib. Percutaneous ultrasound-guided fine-needle aspiration cytology revealed adenocarcinoma and the tumor was diagnosed as bone metastasis from primary lung cancer. A chest wall resection for bone metastasis of right 5th rib was carried out and she underwent adjuvant chemotherapy. She is presently alive and well without recurrence more than 6 years after chest wall resection. CONCLUSION: A resection of bone metastasis from lung cancer may offer the possibility of a long-term survival in selected patients.

[Bronchial artery-pulmonary vein fistula undergoing right upper lobectomy; report of a case].

We report a case of arteriovenous fistula of the bronchial artery. A 42-year-old woman was referred to our hospital because of an abnormal shadow noted on a chest X-ray. A chest computed tomography (CT) scan showed abnormal blood vessels in the right upper lobe. Bronchoscopic examination showed a pulsatile tortuos lesion at the orifice of the right B3 bronchus. Bronchial angiography revealed a convoluted and dilated right bronchial artery and hypervascularization in the right upper lobe. On the basis of a clinical diagnosis of bronchial artery-pulmonary vein fistula, a right upper lobectomy and ligation of the right bronchial artery were successfully performed. Bronchial arteriovenous fistula is rare, and it is risk factor for severe hemoptysis. When the surrounding lung reveals a congestive and organized changes due to the arteriovenous fistula, resection of the affected lung is considered necessary.

[Treatment recommendations for adrenal metastasis of non-small cell lung cancer].

To evaluate the optimum treatment strategy for metastatic adrenal tumors derived from non-small cell lung cancer (NSCLC), we retrospectively analyzed 17 consecutive cases (8 resection cases: 4 synchronous and 4 metachronous: 9 non-resection cases: 3 synchronous and 6 metachronous) who received surgical resection for NSCLC. The patients included 12 males and 5 females with a mean age of 63.9 years. Of these, 9, 3, 2, 2, and 1 patient (s) were diagnosed as having adenocarcinoma, squamous cell carcinoma, pleomorphic carcinoma, large cell carcinoma, and adenosquamous cell carcinoma, respectively. The mean interval after lung resection and treatment of metachronous adrenal metastasis was 9.9 months. The mean time to progression from treatment of metachronous adrenal metastasis to disease progression was 8.9 months. A survival analysis showed no significant prognostic difference between the patient age, gender, pathological stage, synchronous/metachronous classification, CEA, and site of metastases. However, patients who received an adrenalectomy had a more favorable prognosis. The 2-year survival of patients following resection versus those who did not undergo a resection for adrenal metastasis was 62.5 and 22.8%, respectively. These data indicate that metastatic adrenal tumors should be resected if the patient can tolerate surgery after appropriate selection.

Prognostic Factors for Endometrial and Cervical Cancers of Uterus Treated With Immune-cell Therapy: A Retrospective Study.

BACKGROUND/AIM: In this retrospective study, we aimed to investigate the efficacy of immune-cell therapy using T lymphocytes activated in vitro with or without dendritic cell vaccination in combination with standard therapies in terms of the survival of patients with advanced or recurrent endometrial and cervical cancers of the uterus. PATIENTS AND METHODS: A total of 187 patients with advanced or recurrent uterine cancer were enrolled in this study. The correlation between overall survival and various clinical factors was examined by univariate and multivariate analyses. RESULTS: Univariate analysis revealed that the prognosis was improved in uterine cancer patients who received immune-cell therapy without prior chemotherapy or without distant metastasis. Multivariate analysis demonstrated that the absence of prior chemotherapy for endometrial cancer and liver/lung metastasis of cervical cancer are indications for immune-cell therapy. CONCLUSION: Survival benefit in uterine cancer patients could be potentially obtained by a combination of immune-cell therapy with other therapies.

Adoptive Immune-Cell Therapy for the Treatment of Neuroendocrine Carcinoma of the Uterine Cervix.

BACKGROUND/AIM: We aimed to investigate the efficacy of immune-cell therapy in terms of the survival of patients with neuroendocrine carcinoma of the uterine cervix (NECC), which lacks standardized therapeutic approaches. PATIENTS AND METHODS: We identified 17 patients who were diagnosed as having NECC and treated with immune-cell therapy. The clinical characteristics of these patients were extracted from their records and their overall survival was measured. RESULTS: Of the 17 patients, two patients with early-stage NECC without recurrence and three patients with less than four treatments were excluded. The median survival times from the time of diagnosis and from the initial administration of immune-cell therapy were 49.7 and 24.4 months, respectively. The overall survival rates at 1, 2, and 5 years were 63.6%, 38.2%, and 25.5%, respectively. Long-term survival was observed in the patients with distant metastases. CONCLUSION: The preliminary results of this retrospective study suggested the potential efficacy of immune-cell therapy for NECC.

Changes in Immunological Status in Patients With Metastatic Colorectal Cancer Treated With First-line Chemoimmunotherapy.

BACKGROUND/AIM: Chemoimmunotherapy is a promising treatment for various malignant diseases. In this study, we examined whether first-line chemoimmunotherapy using adoptive immune-cell therapy was effective for metastatic colorectal cancer (mCRC). PATIENTS AND METHODS: The therapeutic efficacy and safety of the standard first-line chemoimmunotherapy with adoptive αß T cell therapy and bevacizumab were assessed using thirty-two patients with mCRC in our hospital. Immunological status after this chemoimmunotherapy was also evaluated. RESULTS: The response and disease control rates were 68.8% and 87.5%, respectively. Further, median progression-free and overall survival were 14.2 and 35.3 months. Immunotherapy-associated toxicity was minimal. Significant decrease in the change of monocyte number (p=0.006) and increase in the change of rate of lymphocyte-to-monocyte ratio (p=0.039) were seen in the complete response group. CONCLUSION: First-line chemoimmunotherapy with adoptive αß T cell therapy may be useful for mCRC.

Malignant mesothelioma-associated antigens recognized by tumor-infiltrating B cells and the clinical significance of the antibody titers.

Malignant pleural mesothelioma (MPM) is difficult to diagnose at an early stage. The present study attempted to obtain a tumor-specific antibody against MPM derived from tumor-infiltrating B lymphocytes in MPM by using a xenotransplanted severe combined immunodeficiency (SCID) mouse model, and to identify the antigens recognized by the antibodies. Among the antigen-antibody relationships, the clinical usefulness of antibody titers in the sera was evaluated from the viewpoint of diagnosis of MPM and monitoring of therapeutic effects. Tumor tissue specimens from two patients with MPM were engrafted subcutaneously in SCID mice and blood samples were obtained and pooled every 2 weeks after xenotransplantation until 14 weeks when the mice were killed. A cDNA library was constructed from the mRNA of a MPM cell line (K921MSO). Immunoscreening of the libraries was carried out by serological identification of antigens by a recombinant expression cloning method (SEREX) and four antigens were identified as MPM-associated antigens. Among them, antibody titers against two antigens, Gene-X and thrombospondin-2 (THBS-2), were analyzed by phage plaque assay as the first step. ELISA systems correlated with the phage plaque assay to detect antibody titers against the two antigens were constructed using 20-mer peptides of the antigen-coding genes. The cut-off value was decided by the average and standard deviation of normal healthy persons. Antibody against Gene-X was detected in 10 out of 18 (55.6%) mesothelioma patients and antibody against THBS-2 was detected in 16 out of 18 (88.9%) mesothelioma patients. No patients with lung cancer regardless of asbestos exposure exhibited positive antibody titer against the two antigens. Furthermore, the serum antibody titers decreased after surgical treatment of MPM and increased after recurrence of the disease. The titers of the antibodies against Gene-X and THBS-2 could be used as tumor markers for the diagnosis and follow up of patients with MPM.

Matrix metalloproteinase 12 accelerates the initiation of atherosclerosis and stimulates the progression of fatty streaks to fibrous plaques in transgenic rabbits.

Whether fatty streaks are directly followed by fibrous plaque formation in atherosclerosis remains controversial. Disruption of the basement membrane and elastic layers is thought to be essential for this process. Matrix metalloproteinase 12 (MMP-12) can degrade a broad spectrum of substrates, but the role of MMP-12 in the early stage of atherosclerosis is unclear. To investigate MMP-12 function in the initiation and progression of atherosclerosis, we investigated macrophage migration and elastolysis in relation to fatty streaks in human MMP-12 transgenic (hMMP-12 Tg) rabbits. Fatty streaks in hMMP-12 Tg rabbits fed a 1% cholesterol diet for 6 weeks (cholesterol-induced model of atherosclerosis) were more pronounced and were associated with more significant degradation of the internal elastic layer compared with wild-type (WT) animals. Numbers of infiltrating macrophages and smooth muscle cells in the lesions were increased in hMMP-12 Tg compared with WT animals. In both cuff- and ligation-induced models of atherosclerosis, smooth muscle cell-predominant atherosclerotic lesions were elevated with significant elastolysis of the internal elastic lamina in Tg compared with WT animals; "microelastolytic sites" were recognized before formation of the neointima in the cuff model only. These results indicate that MMP-12 may be critical to the initiation and progression of atherosclerosis via degradation of the elastic layers and/or basement membrane. Therefore, a specific MMP-12 inhibitor might prove useful for the treatment of progressive atherosclerosis.