To find a recommended dose of attIL2-TIL cell therapy that can be given to participant with either relapsed or metastatic sarcomas (has come back or spread to other parts of the body, respectively).

To further test the dose found in Part A to see if it can help to control liposarcoma growth.

Primary Objectives Part A. Determine the safety, maximum tolerated dose and/or recommended phase 2 dose of T cell membrane-anchored tumor- targeted IL12 (attIL12)-TIL cell therapy in combination with cyclophosphamide in participants with advanced/metastatic soft tissue or bone sarcomas Part B. Characterize the safety and tolerability and assess preliminary efficacy of attIL12 TIL cells in combination with cyclophosphamide by evaluating the 4-month progression free survival rate (PFS 4 months) in participants with recurrent unresectable liposarcoma

Secondary Objectives

1) Evaluate the anti-tumor efficacy achieved following adoptive transfer of T cell membrane- anchored tumor- targeted IL12 (attIL12)-TIL cell therapy in combination with cyclophosphamide in participants with advanced/metastatic soft tissue or bone sarcomas

Exploratory Objectives

1. Characterize the immune response following adoptive transfer of attIL12 TIL cell therapy in paired in pre-treatment and on-treatment tumor specimens and peripheral blood samples
2. Assess collagen and FAP changes in pre-treatment and on-treatment tumor specimens and correlate with clinical benefit/anti-tumor response
3. Determine changes in cell surface vimentin (CSV)-positive circulating tumor cells (CTCs) in peripheral blood before and after adoptive transfer of T cell membrane-anchored tumor- targeted IL12 (attIL12)-TIL cell therapy and correlate with clinical benefit/anti-tumor response

Inclusion Criteria:

1. Age ≥ 12 years old
2. Histologically-confirmed locally advanced or metastatic soft tissue or bone sarcoma scheduled to undergo resection or biopsy as part of standard of care
3. Liposarcoma expansion cohort: histologically confirmed unresectable recurrent/metastatic liposarcoma scheduled to undergo resection or biopsy as part of standard of care
4. Participants undergoing resection should have other measurable disease or be high risk for recurrence within 12 month per investigator assessment and has prior approval by PI.
5. Measurable disease according to RECIST 1.1 present prior to infusion of attIL12-TIL. If the only measurable disease is the same as the lesion biopsied for the study, it needs to be at least 2 cm in largest diameter.
6. Participants must have received at least 1 prior line of systemic therapy for the treatment of sarcoma, unless no standard therapy exists for a specific sarcoma subtype.
7. At least 3 weeks must have elapsed since the last cytotoxic chemotherapy or immunotherapy prior to tumor tissue collection. For targeted therapies, at least 4 half-lives or 3 weeks must have elapsed prior to tumor tissue collection (whichever is shorter). Standard of care anti- cancer therapy will be permitted following tumor tissue collection but prior to initiation of cyclophosphamide such that at least 3 weeks must have elapsed since last cytotoxic chemotherapy or immunotherapy prior to starting treatment with cyclophosphamide. For targeted therapies, at least 4 half-lives or 3 weeks must have elapsed prior to initiation of treatment with cyclophosphamide (whichever is shorter). Investigational anti-cancer therapy will not be permitted.
8. At least 2 weeks must have elapsed for palliative radiation to any tumor site other than the tumor site identified for tissue collection
9. Participants must have organ and marrow function as defined below
10. Absolute neutrophil count (ANC) > 1 K/uL, Hemoglobin > 9 g/dL, Platelets > 100 K/mm3
11. Serum creatinine </= 2 mg/dL OR creatinine clearance > 50 mL/min
12. Aspartic transaminase (AST) . 1.5 x upper limit of normal (ULN), Alanine transaminase (ALT) \